One health bacteriology

OneHealth: Open Source Bacteriology
Prof. Dr. Khushi Muhammad
DVM (UAF), M.Sc. (Hons), Microbiology (UAF), PhD, University
of Surrey, UK
Prof. Dr. Masood Rabbani
DVM (CVS), M. Sc. (Hons), PhD (CVS, Lahore, Pakistan)
DEPARTMENT OF MICROBIOLOGY
UNIVERSITY OF VETERINARY AND ANIMAL SCIENCES,
LAHORE
2014

TEAM MEMBERS/CO-AUTHORS
01. Prof. Dr. Khushi Muhammad, Chairman, Department of
Microbiology, UVAS, Lahore
02. Prof. Dr. Masood Rabbani, Director, University Diagnostic
Laboratory (UDL), UVAS, Lahore
03. Prof. Dr. Tahir Yaqub, Director, Quality Operations Laboratory
(QOL), UVAS, Lahore
04. Dr. Imran Altaf, Assistant Professor, QOL, UVAS, Lahore
05. Dr. Aftab Ahmad Anjum, Associate Professor, Department of
06. Dr. Mamoona Ali, Assistant Professor, Epidemiology, UVAS,
Lahore
07. Dr. Ali Ahmad, Assistant Professor, UDL, UVAS, Lahore
08. Dr. Jawad Nazir, Assistant Professor, Department of Microbiology,
UVAS, Lahore
09. Dr. Arfan Ahmad, Assistant Professor, Department of
10. Dr. Muhammad Nawaz, Assistant Professor, Department of
11. Dr. Zubbair Shabbir, Assistant Professor, QOL, UVAS, Lahore
12. Dr. Imran Najeeb, Department of Microbiology, UVAS, Lahore.
13. Dr Haroon Rashid, Lecturer, Pathobiology Department, The
Islamia University Bahawalpur
14. Dr. Muhammad Asad Ali, Lecturer, Department of Microbiology,
UVAS, Lahore
15. Dr. Kashif Hanif, Lecturer, Department of Microbiology, UVAS,
Lahore
16. Dr. Hassan Bin Aslam, Lecturer, Department of Microbiology,
UVAS, Lahore
17. Dr. Fareeha Akhtar, UDL, UVAS, Lahore
18. Dr. Farah Ali, Lecturer, Department of Microbiology, UVAS,
Lahore
19. Dr. Rabia Tahir, Lecturer, Department of Microbiology, UVAS,
Lahore
20. Dr. Muhammad Javed, UDL, UVAS, Lahore
Compiled By,
Haroon Rashid
Chaudhry

Prophet Muhammad (PBUH)
Enunciate Ya Muhammad
Walking the land after Jesus
Completing the work of Abraham
Ending What was started by Moses
Shuning the meat of the ham
The last of the Lord,s undying Legacy
Completing the supreme prophecy
The leader the earth shall never see
Like of him on the earth will never be
The torch bearer of truth and guidance
Leading away the people from Satan and forbiddance
The leader more powerful in stature
A conqueror with a moral nature
Likes of him no mother will yield
No prophet to walk in his field
Guide this servant to the eternal light
For he is in torture and in plight
Haroon Rashid Chaudhry alias Bhulaya, 2013
Dedicated to all the Humanitarians of the world, Abraham (R. A), Moses (R. A.), Jesus (R. A.) and
Muhammad (S.A.W.)
Dedicated to the century old traditions and people which kept the the name of UVAS alive first as
CVS, Lahore-Pakistan and now as UVAS, Lahore-PAKISTAN
Dedicated to the All the veterinarians, helping the voiceless, helpless and the selfless those which
are nurtured to be slaughtered in the name of God and Humanity

Forward
Teacher is a close
apprentice of the
Preacher and the
Preacher has but a
thin line between
the prophet. Science
has evolved as the
new religion on
earth but that does
not mean we forget
the religion most of
the good scientists
are but themselves
very religious and
best of
humanitarians, we
are not leader but
of us are trained
leaders which work
and serve
humanity.

Prokaryotic cell structure, essential and non-essential organelles.
Prokaryotes____ bacteria
Prokaryotic cell structure:
Shape:
 Cocci – round
 Bacilli – rods
 Spirochetes – spiral shaped
 Pleomorphic – bacteria that have many different shapes,
(like jello – spreads out in different shapes)
The shape is determined by the rigidity of the cell wall!
Arrangement:
 Pairs Diplo
 Chains - Strepto
 Grape cluster – Staphylo
Arrangement is determined by degree of attachment at time of cell division. E.g. cocci, diplococci,
streptococci, staphylococci.
Size:
 Range from 0.2 ~ 5 µm.
 The smallest bacteria, Mycoplasma, are about the same size as the largest virus (Pox).
 A largest bacterium is Bacillus Anthracis.
Essential components:
 Nuceloid (genome)
 Cytoplasm
 Cytoplasmic membrane
 Cell wall
 Ribosomes
 Mesosomes
 Periplasm
Non-essential components:
 Capsule
 Pili/Fimbria
 Glycocalyx
 Flagellum
 Spore
 Plasmid
 Granule
Essential organelles:
1. Cell wall
 It is the outer most layer of almost all bacteria.
 Contains antigens which can be identified in the lab.
 It is osmotically resistant and has gram staining properties.
 Its components:
♦ Inner layer
- is peptidoglycan (aka murein/mucopeptide)
- gives support and helps maintain the shape of the cell
- allows cell to withstand low osmotic pressure e.g. H20

- it contains transpeptidase which makes cross-linking between two tetrapeptidase ^ so it’s
a good target for drugs (penicillin inhibits synthesis of peptidoglycan by inhibiting
transpeptidase)
- it is much thicker in G+ bacteria.
♦ Outer membrane:
- is found in G- bacteria only and consists of:
- Lipopolysaccharide (LPS) is an endotoxin
- Lipoprotein
- Phospholipids
- Porin proteins -allows passage of sugars, amino acids, vitamins and penicillin
 Specific components of G+ cell wall:
♦ Teichoic acid: consist of glycerol and orbital phosphate and is of medical importance as
induces septic shock & mediates attachment to mucosal cells.
♦ Lipoteichoic acid: is a glycerol teichoic acid that penetrates the
peptidoglycan layer and links covalently to lipids in the cytoplasmic
membrane.
 Specific components of G- cell wall:
♦ Lipopolysaccharide (LPS):
- is an endotoxin (endotoxins are part of cell wall while exotoxins are released from cell)
- it is responsible for features of disease : fever, shock
- has 3 parts:
 Lipid A- is a phospholipids responsible for toxic effect
 Core polysaccharide
 Outer polysaccharide called O-antigen- is used in lab
identification of bacteria.
♦ G- organelles-are associated with O, H and K antigens.
O = LPS, H = flagella, K = capsule.
2. Cytoplasmic membrane:
 Consist of phospholipids bilayer, does NOT contain sterols like Mycoplasma and eukaryotes do.
 Functions:
♦ Active transport into cell.
♦ Energy production through oxidative phosphorylation.
♦ Synthesis precursors of cell wall.
♦ Secretes enzymes and toxins.
3. Mesosome
 Is an invagination of cytoplasmic membrane.
 It is important for cell division - where it forms the transverse septum.

 It is the binding site for DNA.
4. Cytoplasm
 Has 2 regions:
♦ Amorphous matrix-which contains:
- Ribosomes
- Nutrient granules
- Metabolites
- Transposons (carry important genes)
- Plasmids (can be the following: antibiotic resistant, exotoxin, resistant to heavy metals
and UV light, pili, bacteriocin - lethal to other bacteria)
♦ Inner nucleoid region -consist of DNA
5. Ribosomes
 Site of protein synthesis and where drugs perform their actions.
6. Nucleoid
 Location of DNA (prokaryotic DNA is single stranded and circular)
 DNA has no introns.
7. Periplasmic space (only in G-)
 Space between outer membrane and cytoplasmic membrane.
 Contains ß-lactamase that degrades penicillin and other ß-lactamase drugs.
Non essential organelles:
1. Capsule.
 Gelatinous layer covering the entire bacteria
 Consist of polysaccharides
 Importance:
♦ Determines the virulence of bacteria, since it inhibits it from being eaten by other bacteria
etc = antiphagocytic effect.
♦ Important for specific identification of bacteria ^ in presence of homologous antibodies, the
capsule will swell. The swelling (Quellung reaction) is important for identifying the
organism.
♦ Capsular polysaccharides are used as antigens in certain vaccines - because they can elicit
some antibodies.
♦ Helps in adherence of bacteria to human tissue (= first step of infection).
2. Flagella.
 Responsible for bacterial locomotion. Helps move the bacteria towards nutrients chemotaxic.
 Composed of flagellin protein.
 Energy for movement is made by ATP.
 Only RODS have flagella! Cocci do not and spirochetes use axial filaments for movement.
 The number and location
of flagella varies:
♦ Monotrich
♦ Ampitrich
♦ Lophotrich
♦ Peritrich
3. Pili (Fimbria).
 Hair like filaments - short and straight.
 Made up of protein pilin.
 Found mainly in G- bacteria
 Importance:
♦ Mediate attachment of bacteria to receptors on human cell surface - initiates infection.
♦ Sex pilus makes attachment between male and female during conjugation.
4. Glycocalyx (slime layer).
 Polysaccharide coating
 Helps bacteria adhere strongly to different structures (skin, heart valves, catheters etc).
 Importance in plaque formation ^ in dental caries (S. Mutans).
5. Spore.
 Resistant to heat and toxins


6. Plasmid.
 DNA, contain genes for antibiotic resistance and toxins.
7. Granules.
 Site of nutrients in cytoplasm.

ANTIBACTERIAL DRUGS
Importance of antimicrobial therapies is selective toxicity: selective inhibition of the growth of
microorganisms without damaging the host. So it should be very toxic to the bacteria, but not/very little
toxic to humans. This is done by using the difference between metabolism and structure of the
microorganism & the features of the human cell.
Major site of action for bacterial drugs:
 Cell wall
 Ribosomes
 Nucleic acid
 Cell membranes
Major groups of antibacterial drugs.:
 Broad spectrum drugs: are active against several types of organisms, e.g. cephalosporins,
aminoglycosides, tetracyclins.
 Narrow spectrum drugs: are active against one or very few types of microorganisms, e.g.
vancomycin for staphylococci and enterococci only.
 Bactericidal drugs: kills the bacteria
 Bacteriostatic drugs: inhibits the bacteria’s growth, but doesn’t kill it.
 Chemoprophylaxis drugs: are used to prevent disease, e.g. penicillin and ampicillin. Used in 3
circumstances:
♦ Prior to surgery
♦ In immunocompromised patients
♦ In people who have been exposed to an organism.
When choosing a drug, one should be aware of:
 sufficient therapeutic concentration,
 appropriate dosage and timing.
Antibiotics with bactericidal effect:
1. Penicillin
2. Cephalosporins
3. Aminoglycosied
4. Fluroquinolons
Broad spectrum penicillin derivatives for both G- and G+:
1. Ampicillin
2. Amoxicillin
3. Piperacillin
4. Azlocillin
5. Mezlocillin

Mechanism of action of antibacterial drugs.
 Inhibition of cell wall synthesis:
♦ Penicillin
- Binds to active site of transpeptidase and in this way inhibits peptidoglycan synthesis (which is
needed for the cell’s structural support).
- Exposure to penicillin activates autolytic enzymes that degrade the bacteria. If these autolytic
enzymes are not activated, the bacteria are not killed - seen in some strains of Staphylococcus
Aureus (said to be tolerant).
- It kills bacteria when they are growing i.e. when they are synthesizing new peptidoglycans.
Penicillins are thus more effective/active during the log phase/exponential phase than during
lag phase.
- Both penicillin and cephalosporin are ß-lactam drugs, meaning an intact ß-lactam ring is
needed for activity. Without it, they won’t work
- Hypersensitivity to penicillin is a growing problem.
- All penicillin family antibiotics have ß-lactam ring, this is why they are called fi-lactam
antibiotics. Penicillin passes through channels in the cell wall called porin - then the ß-lactam
ring binds to and inhibits the transpeptidase enzyme -} cell wall synthesis gets arrested and the
cell dies. So in order to be effective, the P-lactam penicillin must:
 Penetrate th e cell layers
 Keep its ß-lactam ring intact
 Bind the transpeptidase
- The purpose of using ß-lactamase inhibitors in antibacterial therapy is that the combination of
ß-lactamase inhibitors (eg. clavulanic acid or sulbactam) with ß-lactamase sensitive penicillins
(e.g. amoxicillin or ampicillin) can overcome resistance mediated by many but not all
lactamase.
♦ Cephalosporins
- Is structurally same as penicillin - both have ß-lactam ring.
- Inhibits cross-linking of peptidoglycan.
- Has a broad range, well tolerated and fever hypersensitivity reactions than penicillin.
- First generation cephalosporins are mainly active against G+ cocci, while 2nd
, 3rd
and 4th
generation cephalosporins have expanded to also act against G+ rods.
♦ Vancomycin
- Is a glycopeptide - not a ß-lactamase.
- It inhibits cell wall synthesis in G+ bacteria by blocking transpeptidase.
 Inhibition of protein synthesis:
♦ Aminoglycosides
- Acts on 30s subunit of bacteria.
- It inhibits bacterial protein synthesis by binding to 30s subunit, which blocks the initiation
complex. No peptide bonds are formed and no polymerases are made.
- Are a family of bactericidal drugs which include:
 Gentamicin
 Tobramycin
 Streptomycin
 Amikacin
♦ Tetracyclines
- Acts on 30s subunit of bacteria.
- Inhibits bacterial protein synthesis by blocking the binding of aminoacyl t-RNA to the 30s
ribosomal subunit.
- Effective against both G+ and G-.
♦ Chloramphenicol
- Acts on 50s subunit.
- Inhibits bacterial protein synthesis by blocking peptidyl transferase ^ the enzyme that adds new
amino acids to the growing polypeptide.
- Effective against G+, G- and anaerobes.
-
♦ Erythromycin
- Acts on 50s subunit
- Inhibits bacterial protein synthesis by blocking the release of the t-RNA after is has delivered its
amino acids to the growing polypeptide.
- Erythromycin is a member of the macrolides family.

- Has wide spectrum of activity.
♦ Clindamycin
- Acts in the same way as erythromycin
- Effective against many anaerobic bacteria.
 Inhibition f nucleic acid synthesis:
♦ Sulfonamides & Trimethoprim
- Inhibit the synthesis of folic acid, the main donor of the methyl groups that are needed for
synthesis of adenine, guanine and thymine.
- A combination of both is often used because bacteria resistant to one drug will often be
inhibited by the other.
♦ Quinolones
- Inhibit DNA synthesis by blocking the DNA gyrase ,the enzyme that unwinds DNA strands so
that they can replicate.
- They are a family of drugs.
♦ Rifampin
- Inhibits RNA synthesis in bacteria by blocking RNA polymerase, which synthesizes RNA.
 Altering cell membrane function:
Anti-fungal drugs are the most important in this category, because fungal cell membranes contain ergosterol,
while human cell membranes have cholesterol. Bacteria, with exception of Mycoplasma, don’t have sterols in
their membranes and thus are resistant to these drugs.
♦ Amphotericin B
- Disrupts fungal cell membrane by binding to the site of ergosterol in the membrane.
- It is used to treat systemic fungal infection, but it has side effects, especially on kidneys.
♦ Azoles
- Are antifungal drugs that inhibit ergosterol synthesis.
- The azole family is useful in systemic as well as skin and mucous membrane infections.
 Additional drug mechanisms:
♦ Isoniazid
- Inhibits the synthesis of mycolic acid, a long chain fatty acid found in cell of mycobacterium.
- It is a prodrug that requires a bacterial peroxidase (catalase) to activate the isoniazid to become
the metabolite that inhibits mycolic acid synthesis.
- Isoniazid is the most important drug in treatment of tuberculosis + other mycobacterial
diseases.
♦ Mitronidazole
- Is effective against bacteria and certain protozoa because it acts on electron sink ^ it takes
away the electrons the organism needs to survive.
- It also forms toxic intermediates which damage DNA.

♦ Chemoprophylaxis
- These antimicrobial drugs are also used to prevent infectious diseases.
- They are given mainly in 3 circumstances:
 To prevent surgical wounds from getting infected
 To prevent opportunistic infections in immunocomprised patients
 To prevent infections in those known to have been exposed to pathogens that can cause
serious infectious diseases.
Bacterial resistance to antibacterial drugs: significance and mechanisms of action.
The 4 mechanisms of antibiotic resistance are:
1. Enzymatic degradation of the drug.
2. Modification of the drugs’ target.
3. Reduced permeability of the drug.
4. Active export of the drug.
Most drug resistance is the result of a genetic chance in the organism, caused either by a chromosomal
mutation or acquisition of a plasmid or transposon.
 Genetic basis of resistance
♦ Chromosomal mutation
- Either changes the target of the drug so the drug won’t be able to bind, or it changes the
membrane so that the drug doesn’t penetrate well into the cell.
- This occurs at low frequency, affecting only one drug or one family of drugs.
♦ Plasmids
- Cause drug resistance by encoding enzymes that degrade or modify the drug.
- This happens at higher frequency, affecting multiple drugs.
♦ Transposons
- Are small pieces of DNA that move from one site on the bacterial chromosome to another or
from one bacterial chromosome to plasmid DNA.
- They often carry drug resistant genes.
 Non genetic basis of resistance
♦ Non genetic reason why bacteria may not be inhibited by antibiotics are that drugs may not be
able to reach the bacteria located in the middle of an abscess and also that certain drugs, like
penicillin don’t affect bacteria that are growing. The presence of foreign bodies also makes it
more difficult to achieve a successful antibiotic treatment.
 Specific mechanism of resistance
♦ Resistance to penicillin and cephalosporins is mediated by 3 mechanisms:
- Degradation by ß-lactamase (THE MOST IMPORTANT MECH.!)
- Mutation in genes for penicillin binding proteins.
- Reducing permeability.
Antibiotic sensitivity testing
 The minimal inhibitory concentration (MIC) is the lowest concentration of drug that inhibits the
growth of the bacteria isolated from the patient. In this test though, it isn’t known if the inhibited
bacteria have been killed or just stopped growing.
 The minimal bactericidal concentration (MBC) is the lowest concentration of drug that kills the
bacteria isolated from the patient. In certain diseases, like endocarditis, it is important to use a
concentration of drug that is bactericidal.
Use of antibiotic combination
 Two or more antibiotics are used under certain circumstances, like in life threatening infections
before the cause has been identified, to prevent the emergency of resistant bacteria during prolonged
treatment regimes, and to
achieve a synergic effect.
Synergism:when the effect of two drugs together is significantly higher than the sum of the effect of the
two drugs alone.
Antagonism:when the effect of the two drugs together is significantly lower than the effect of the effective
drug alone.

Sterilization
Sterlization is killing or removing all microorganisms, including spores, in a physical matter.
Usually done by:
 Autoclaving
 Hot air oven (dry heat)
 Gamma radiation
 Filtration (fluids)
 Gas sterilization
(NOT boiling, UV or pasteurization!!)
Heat can be applied in 3 ways:
 Moist heat (boiling or autoclaving0
 Dry heat
 Pasteurization
In general, heat kills by denaturing proteins, but membrane damage and enzymatic cleavage of DNA are
also involved.
 Autoclaving
♦ Is the most frequent used method of sterilization.
♦ Moist heat sterilization at 121C pressure for 15-10 min!
♦ It also kills spores. Since spores are resistant to boiling (100C), they must be exposed to higher
temp., and autoclaving achieves this. This is the reason why it is favored.
 Hot air oven (dry heat)
♦ Used less frequently than autoclaving.
♦ In hot hair oven at 180C for 2 hours!
♦ Used for sterilization of glass equipment.
 Gamma radiation
♦ Has high energy (higher than UV) and penetrating power.
♦ It kills mainly by producing free radicals ->these radicals can break covalent bonds in DNA
and thereby killing the organism.
♦ Used for sterilization of heat sensitive items like suture material, surgical gloves and plastic
items like syringes.
 Filtration
♦ Is preferred when it comes to sterilization of fluids e.g. those with heat sensitive components.
♦ The membrane filters (cellulose esters) have usually pores the size of 0.22 µm - this is the size
of the smallest bacteria (so the bacteria won’t be able to go through the pore).
♦In the past, solutions for intravenous use were autoclaved, but the heat resistant endotoxins in the
cell wall of dead G- bacteria would cause fever in the patient, so now solutions are filtered to
make them pyrogen-free before they are autoclaved (IF autoclaved).
 Gas sterilization
♦ Ethylene gas is used extensively in hospitals for sterilization of heat sensitive materials, like
surgical instruments and plastics.
♦It kills by alkylating both proteins and nucleic acid.
Disinfectants
Disinfection is the killing of many, but not all, microorganisms.So basically, if you can’t kill them,
you are at least reducing their number. And this is done in a chemical way. Chemicals that are used to kill
microorganisms on the surface of skin and mucous membranes are called antiseptics.
The major groups of disinfectants are:
 Alcohol
 Aldehydes (alkylating agents)
 Phenol derivatives
 Detergents
 Chlorine
 Iodine
(Chlorine and iodine are oxidizing agents)
The main modes of action of disinfectants are:
1. Damaging lipid containing cell membranes
2. Modification of proteins
3. Modification of DNA

1.Chemical agents which damage the cell membrane.
 Alcohols
♦ Ethanol
- Widely used to clean the skin before immunization or venipuncture.
- Functions mainly by disorganizing the lipids structure in membranes,
but it also denatures proteins.
- Ethanol needs the presence of water for max effect ->it works better at
70% than 100% alcohol.
♦ Isopropanol.
 Detergents
They have a hydrophilic and hydrophobic group.Chemically they are classified as cationic, anionic, and
non-anionic (not important in microbiology):
♦ Cationic detergents
- Are more effective than the anionic ones.
- It reacts with the lipids in the cell membrane through its hydrophobic chain and the
surrounding water through their polar groups ->this way they disrupt the membrane.
- Its most known compound is the Quaternary Ammonium Compound (e.g. ammonium
chloride) ->used to disinfect skin.
- They work at alkaline pH.
- Advantages: has low toxicity, high stability in water and stable in solutions.
♦ Anionic detergents
- Are the soaps and fatty acids.
- Damage the lipids of the cell membrane.
- Effective in acidic pH.
- Not that effective against G- bacteria.
Note: the cationic and anionic detergents may neutralize each other!
 Phenols
♦ Was the first disinfectant used in the operating room by Lister in 1860s, but rarely used today.
♦ Damage membranes and denature proteins.
♦ The 5% solutions can be used to disinfect materials like sputum, urine, feces and contaminated
instruments and utensils.
♦ Their activity is reduced at alkaline pH, organic material, low temp., or presence of soap.
♦Examples: cresol, hexachlorophene, chlorohexidine.
2.Disinfectants which modify/denature proteins.
 Chlorine
♦ Used to purify water supply and to treat swimming pools
♦ Component of bleach, Clorox ->used as disinfectant in homes and hospitals.
♦ Is it a powerful oxidizing agent.
 Iodine
♦ Most effective skin antiseptic used in medical practice ->used to disinfect skin prior to obtaining
blood culture and installing intravenous catheter - to kill natural flora.
 Acids, alkaline and organic dissolvent
♦ Denature proteins
♦ Useful for preservation of food;
♦ E.g. benzoic acid, lactic acid, acetoic acid.
 Heavy metals
♦ Mercury and silver react with SH-group of enzymes and form mercaptoid - like this they
prevent enzymatic activity.
♦ Mercury used in skin antiseptics.
♦ Silver nitrate drops useful in preventing infection by N. Gonorrhea.
3.Agents that modify functional groups of proteins and nucleic acid.
 Aldehyde (alkylating agents)
♦ The two most effective Aldehydes are formaldehyde and glutaraldehyde.
♦ The alkylation of proteins leads to irreversible inhibition of enzymes.
♦ Room temp and relative humidity between 60 - 80% is necessary.
Bacterial virulence factors.
 Virulence: is a quantitative measure of pathogenicity. It is measure by the number of organisms
needed to disease.
♦ 50% lethal dose (CD50) - is the number of organisms needed to kill half of the hosts.
♦ 50% infectious dose (ID50) - is the number of organisms needed to cause infection in half
of the host.
The infectious dose of a bacterium depends on their virulence factors. For example if their pilus allows
them to adhere well to the mucous membranes, whether they produce exotoxins or endotoxins, whether
they have a capsule, if they can survive the different non-specific host defense like acids in stomach

Adherence to cell structures
1. Pili
 Is the main mechanism of adherence to human cells.
 They extend from the surface of bacteria and mediate attachment to specific receptors on cells.
2. Glycocalyx
 Is a polysaccharide “slime layer” secreted by some strains of bacteria.
 It mediates strong adherence to certain structures like heart valves, prosthetic implants and
catheters.
3. Fimbria
Binding to tissue
The different molecules that mediate adherence to cell surfaces are called adhesin.
Invasion and intracellular survival.
Invasion of tissue is enhanced by enzymes secreted by bacteria e.g. hyaluronidase and collagenase secreted
by S. Pyogenes degrades hyaluronic acid in subcutaneous tissue ->this allows the organism to spread
rapidly.
1. IgA protease
degrades secretory IgA - allowing bacteria to attach to mucous membrane e.g. in mouth.
2. Coagulase
accelerates the formation of a fibrin clot from its precursor form ->it clots plasma.
3. Capsule
surrounds the bacteria
antiphagocytic.
4. M-protein
found in cell wall of G+ cocci
antiphagocytic.
5. Protein A
founds in cell wall of G+ cocci
 binds to IgG and inhibits complement binding to bacteria.
Intracellular survival -once the bacterium is inside the body it protects itself by avoiding attack by
macrophages and neutrophils;
 Inhibits fusion of phagosomes with lysosomes - like this is avoids the enzymes of the lysosome.
 Inhibits acidification of phagosomes - reduces the activity of lysosmal degredative enzymes.
 Escapes from phagosomes in cytoplasm where there are degredative enzymes.
 Leucocidin (by S. Aureus) - kills macrophages and leukocytes.
Toxin production.
Is the second major way bacteria cause disease.
 Exotoxins
♦ Produced by both G+ and G- bacteria
♦ They are polypeptides secreted by certain bacteria and alter specific cells functions resulting in
symptoms of disease.
♦ Found in plasmids or bacterial Lysogenic viruses.
♦ Most toxic substance known.
♦ They are antigenic and induce antibodies called antitoxins.
♦ They have an A (active) subunit ->is an enzyme (ADP ribosylation) + has toxic activity and B
(binding) subunit.
♦ They have different mechanism of action and different targets within the cell and therefore
cause many different diseases with characteristic symptoms; some act by proteolytic cleavage
of cell component, while others act as superantigens causing overproduction of cytokines.
♦ When the exotoxins are treated with formaldehyde (or acid/heat), they convert into toxoids
which are used in protective vaccines because they keep their antigenicity but have lost their
toxicity.
♦ Types
1. Neurotoxins are exotoxins that act on nerves or motor endplates to cause paralysis e.g.
tetanus toxin, botulinum toxin.
2. Enterotoxins are exotoxins that act on GI tract to cause diarrhea. They inhibit NaCl
absorption and activate NaCl secretion or mediate destruction of epithelial cells. End result
is fluid accumulation in intestines ->diarrhea.
Enterotoxins cause 2 disease manifestations:
a) Infectious diarrhea ->bacteria colonize and bind to the GI tract and continuously

release their enterotoxins until they are killed by the immune system or by antibiotics.
b) Food poisoning ->bacteria grow in food and release enterotoxins in food, the
eneterotoxin is then ingested leading to diarrhea and vomiting.
3. Pyrogenic exotoxins stimulate release of cytokines and cause rash, fever and toxic shock
syndrome.
4. Tissue invasive exotoxins allow bacteria to destroy and funnel themselves through tissues.
These induce enzymes that destroy DNA, collagen, fibrin, NAD, RBC and WBC.
5. Miscellaneous exotoxins are the main virulence factors of many bacteria - can cause
disease unique to the individual bacteria.
 Endotoxins
♦ Only in G- rods and cocci.
♦ They are part of the cell wall (so not secreted!).
♦ Are lipopolysaccharides (LPS).
♦ They all produce the same general effect: fever and shock.
♦ Weakly antigenic ->they produce weak antibodies, so multiple episodes may occur.
♦ They don’t produce toxoids, so not used in vaccines.
♦ They are the cause of septic shock, seen in intensive care units.
- In septic shock it s the bacteria itself that is circulating in the blood, while in toxic shock it
is the toxin., so blood cultures are positive for septic shock, but negative for toxic shock.
- Septic shock causes death of patient even though the antibiotics have killed the bacteria in
the blood. This is because septic shock is mediated by cytokines like TNF and IL-1 that
continue to act even thought the bacteria that induced them has been killed.
♦ The toxic part of LPS is Lipid A ->causes the overproduction of cytokines.
♦ Biological effects of endotoxins include:
1. Fever - due to release of endogenous pyrogen (IL-1) by macrophages ->act on temp.
center in hypothalamus.
2. Hypotension - leads to shock and decreased perfusion of essential organs, caused by
bradykinin which increases vascular permeability.
3. Disseminated Intravascular Coagulation (DIC) - due to activation of coagulation
system through Hageman factor leading to thrombosis and tissue ischemia leading to
organ failure.
4. Activation of alternative pathway of complement cascade leading to inflammation and
tissue damage.
5. Activation of macrophages ->increasing their phagocytic ability and activating antibody
production.
PROPERTY EXOTOXIN ENDOTOXIN
Source Some bacteria of G+ and G- bacteria Cell wall of G- bacteria
Secreted from cell Yes No
Chemistry Polypeptide Lipopolysaccharide
Location of genes Plasmid or bacteriophage Bacterial chromosome
Toxicity High (fatal dose at 1µg) Low (fatal dose at hundreds of µg)
Clinical effect Various Fever and shock
Mode of action Various Induces TNF and IL-1
Antigenicity Induce high antibody titer, antibodies
called antitoxins
Poorly antigenic
Vaccines Toxoids used as vaccine No toxoids formed and no vaccine available
Heat stability Destroyed rapidly at 60% (except
staphylococcal enterotoxin)
Stable at 100C for 1 hour
Typical disease Tetanus, botulism, diphteria Meningococcemia, sepsis by G- rods

Exotoxins by G + bacteria
Bacteria Exotoxins Action & Effects
Corynebacterium DiphteriaDiphteria toxin Inhibits protein synthesis by inactivating elongationfactor 2 (EF-2).
Clostridium
Tetani
Tetanus toxin Is a neurotoxin – prevents release of neurotransmitters.
It stops the release of glycine (inhibitory), so excitatoryneuronsarenot unopposedleadingto
muscle spasm and spastic paralysis (lock jaw).
Clostridium
Botulinum
Botulinum toxin Is a neurotoxin – prevents release of neurotransmitters. It stopsthereleaseofacetylcholine
(excitatory) at synapse leading to flaccid paralysis.
Clostridium
Difficile
Exotoxin B Is a cytotoxin – damages the colonic mucosa causing pseudomembraneformationandalso
destroys actin filaments in the cytoskeleton leading to apoptosis.
Clostridium Perfringes
& other Clostridia
species
They all facilitate in the
spread of gas gangrene!
Alpha toxin Is an enzyme (lecithinase) – hydrolyzes lethicin in cell membraneleadingtodestructionof
membrane and cell death.
Collagenase Is an enzyme that breaks peptide bonds in collagen.
Protease Is an enzyme that catalyzes the hydrolytic breakdownofproteinsintopeptidesoraminoacids
and thereby destroying extracellular structures.
Hyaluronidase Is an enzyme that catalyzes the breakdown of hyaluronic acid in the
body, thereby increasing tissue permeability to fluids. Also called spreading factor.
Deoxyribonuc-
lease (DNase)
Is an enzyme that catalyzes the hydrolysis (depolymerization) of DNA.
The 7 lethal
factors
Have hemolytic and necrotizing activity.
Bacillus Anthracis
(agent of anthrax)
Edema factor Is an adenylate cyclase that increases the cyclic AMP concentration
in the cell,leadingtoloss ofchloride ions andwater resultingin edema formation in tissue.
Lethal factor Is a protease – it cleaves phosphokinase which is neededforthesignaltransductionpathways
that control cell growth. Loss of phosphokinase means the cell isunabletogrowleadingto
death.
Protective
antigen
Binds to cell surface receptors and forms pores in cell membrane which allowstheedema
factor and lethal factor to enter the cell.
S. Aureus Toxic shock syndrome
toxin (TSS)
Is a superantigen - binds directly to class II MHC proteins on surface ofantigenpresenting
cells (macrophages) ^will interact with T -cells leading to release of large amounts of
interlukins (IL1 and IL2).
Staphylococcal
enterotoxin
Is a superantigen, but because it is ingested in acts locally on lymphoid cells liningsmall
intestines. Causes foodpoisoning1-6hours after ingestion ^ vomitingandwatery diarrhea.
Exfoliatin Is a protease – causes scalded skin syndrome.
S. Pyogenes Erythrogenic
toxin
Is a superantigen – causes rash seen in scarlet fever.
Exotoxins by G - bacteria
E. Coli Heat-labile
enterotoxin
Stimulates adenylate cyclase activity in cells of small intestines -^
increased concentration of cyclic AMP fluid and electrolyte loss ^
watery, non bloody diarrhea.
Heat-stabile
enterotoxin
Increases concentration of cyclic GMP ^ inhibits reabsorption of
sodium ions ^ diarrheaVerotoxin aka
Shigella like
toxin
Produced by strains of E.Coli that have O157:H7
serotype – causes bloody diarrhea.
V. Cholera &
Bacillus Cereus
Enterotoxins Act in the same manner as heat-labile toxin –
cause diarrhea.B. Petrussis Petrussis Toxin Causes whopping cough - catalyzes transfer of ADP
ribose from NAD to an inhibitory G-protein increases
cyclic AMP ^ edema and cough. Also inhibits signal transduction pathwayofchemokine
receptors causing lymphocytosis.

Transmission of infections, portals of entry of pathogenic microbes.
 Mode of transmission
♦ Human-to-human
- Direct contact - intimate contact, sexual passage through birth.
- No direct contact - faecal-oral (ingestion of contaminated food etc), finger to mouth.
- Transplacental - across placenta, from mother to baby.
- Blood-borne - blood transfusion, intravenous drug use.
 Vertical transmission: from mother to baby (transplacental, through birth canal, breast
milk).
 Horizontal transmission: all other pathways.
♦ Non human-to-human
- Soil source - spores in soil enter wounds.
- Water source - bacteria in water aerosol are inhaled into lungs.
- Fomite source - bacteria in object e.g. towel ->transferred to skin.
- Animal source
 Directly - bacteria enter through cat scratch.
 Via insect vector - bacteria enter via tick bite.
 Via animal feces - bacteria in cattle feces ingested in undercooked hamburgers.
 Portals of entry
♦ Respiratory tract, e.g. pneumonia, meningitis, tuberculosis.
♦ G.I. tract, e.g. typhoid fever, cholera, dysentery.
♦ Skin, e.g. tetanus, Rocky Mountain spotted fever.
♦ Genital tract, e.g. gonorrhea, syphilis, urethritis.
 Stages of bacterial pathogenesis
♦ Transmission from external source into portal of entry.
♦ Evasion of primary host defense like skin or stomach acid.
♦ Adherence to mucous membrane (usually by pili).
♦ Colonization by growth of bacteria at site of adherence.
♦ Disease symptoms caused by toxins product or invasion (accompanied by inflammation).
♦ Host response (non-specific + specific), during steps 3, 4 and 5.
♦ Progression and resolution of disease.
Non - specific defenses against pathogenic microbes.
Innate (non-specific) defense protects against microorganisms in general. It can be classified into 3
categories:
1) Physical barrier ->skin or mucous membranes.
2) Phagocytic cells ->e.g. neutrophils, macrophages, NK cells.
3) Proteins ->e.g. complement, lysosomes and interferon.
 Physical barrier - loss of physical barrier predisposes to infection.
♦ Skin:
- Intact skin is the first line of defense.
- Provides protection both as a physical barrier and also via the fatty acids secreted by the
sebaceous glands in the skin, which have antibacterial and antifungal properties.
- The skin’s low pH (3-5), provided by the fatty acids, also has an antimicrobial effect.
♦ Mucous membrane of respiratory tract:
- Lined with cilia and covered by mucous ->mucous will more the mucosa to the nose and
mouth where the bacteria will be trapped and expelled.
- This “ciliary elevator” can be damaged by alcohol, smoking and viruses ->damage will
predispose host to bacterial infection.
- Other protective mechanisms in resp. tract:
 Macrophages
 Lysozyme
 Hairs in nose
 Cough reflex - prevents bacteria from entering the lungs

♦ Protection in G.I. tract by:
- Hydrolytic enzymes in the saliva (lysosome and secretory IgA).
- Acid in stomach (very low pH).
- Degredative enzymes and macrophages in small intestines.
- Panet cells in small intestines ->produce lysosomes.
♦ Vagina
- Protected by low pH provided by lactobacilli (part of normal flora).
♦ Bacteria of normal flora of skin, nasopharynx, colon and vagina
- Bacteria of normal flora of skin, nasopharynx, colon and vagina also provide protection by
not allowing pathogens to multiply at these sites..
♦ Defensins
- positively charged (cationic) peptides that create pores in membranes of bacteria, and thereby
killing them. They are found in different places of the body.
- Neutrophils and Panet cells in the intestinal crypts of G.I. contain a-defensin.
- Respiratory tract produces ß-defensin.
 Inflammatory response and phagocytosis
♦ The presence of foreign bodies (bacteria) will provoke a protective inflammatory response - it is
characterized by clinical findings like: redness, swelling, warmth at site of infection.
♦ The signs are due to increased blood flow, increased capillary permeability and the escape of
fluid from cell into tissue spaces.
♦ The increase in permeability is due to chemical mediators: histamine, prostaglandins and
leukotriens. Complement components (C3a, C5a) also increase permeability, while bradykinin
is a mediator of pain.
♦ Macrophages and neutrophils are the most important cells in inflammatory response.
Neutrophils are predominant in acute pyogenic infection, while macrophages are predominant in
chronic granulomatous infection.
♦ Macrophages are both antiphagocytic and produce two important “pro-inflammatory” cytokines:
IL1 and TNF.
♦ Neutrophils and macrophages are attracted to site of infection by chemokines ->small
polypeptides produced by cells at the infected site. IL8 and C5a are the most important
chemokines of neutrophils.
♦ Both neutrophils and macrophages are phagocytic cells, but macrophages are also antigen
presenting cells to CD4 positive (helper) T-cells (neutrophils are not antigen presenting cells).
♦ In response to bacterial infection, there will be an increase in number of neutrophils in blood.
This increase is caused by production of granulocyte stimulating factor by macrophages. After
neutrophils are attracted to the site of infection, they attach to the endothelium via ICAM protein
(on endothelium) and selectin (on endothelium) - integrin (on neutrophils) coupling neutrophils
will migrate through endothelium (diapedesis) and ingest the bacteria. Recurring pyogenic
infection occurs in those who have inadequate neutrophils.
♦ Infection causes an increase in body temperature (fever) which is attributed to endogenous
opiates (IL-1) released by macrophages. This is a protective response since many bacteria and
viruses grow slower in higher temperatures.
♦ The importance of inflammatory response to limit infection is emphasized by the ability of anti-
inflammatory agents like corticosteroids to lower resistance to infection.
♦ There are two main types of host defenses against bacteria:
1. Pyogenic response = pus producing response.
- Pyogenic bacteria are often called “extracellular pathogens” because they don’t invade the
cell e.g. S. Aureus, S. Pyogenes.
- This response involves the action of antibodies, complement and neutrophils.
2. Granulomatous response
- These bacteria invade and survive inside the cell and thus called “intracellular pathogens”
e.g. Mycobacterium Tuberculosis, Listeria Monocytogens.
- Response involves macrophages and CD4 helper T-cells

Specific immune response against pathogenic microbes.
Acquired Immunity (= specific immunity) is obtained either from exposure to the organism itself
(active immunity) or from receiving preformed antibodies made in another host (passive immunity).
 Passive acquired immunity
♦ Protection based on the transfer of preformed antibodies (in serum) from one person (or animal)
to another person.
♦ Its important advantage is that its protective ability becomes present immediately (while in
active immunity, it takes a few days/weeks).
♦ Its main disadvantage is that the antibody concentration decreases fairly fast as the proteins are
degraded. So protection usually lasts only for a few months.
♦ Passive immunity also occurs naturally when immunoglobulins are passed through placenta
(IgG) or breast milk (IgA) from mother to child.
 Active acquired immunity
♦ Refers to protection based on exposure to the organism in the form of overt disease; subclinical
infection (infection without symptoms) or a vaccine.
♦ It is mediated by both antibodies (immunoglobulins) and T-cells (cell-mediated)
♦ Has slower onset, but longer duration than passive - primary response usually takes 7-10 days
for antibodies to become detectable.
♦ An important advantage of active immunity is that an anamnestic (secondary) response occurs,
meaning there is a rapid response (~3days) of a larger amount of antibodies to an antigen that
the immune system has been exposed to before.
♦ Essential host defense
- Antibody mediated (humoral immunity) ->against encapsulated pyogenic bacteria and
exotoxins.The role of specific antibodies in antibacterial immunity:
 Neutralization of exotoxins and enzymes
 Complement dependent bacteriolysis (G-negative)
 Opsonisation (helping phagocytosis)
 Interfering with attachment of bacteria to mucosal surfaces
- Cell-mediated ->against intracellular bacteria (macrophages and helper T-cell) and virus
infected cells (cytotoxic T-cells).
- Reduced host defense results in an increase in frequency and severity of infection. Main
causes include:
 Different genetic immunodeficiencies (low antibody-, complement-, neutrophil- or CD4
cells number).
 Presence of foreign bodies (urinary/intravenous catheter, prosthetic heart valves,
prosthetic joints etc).
 Presence of certain chronic diseases like diabetes and renal failure.
- IgG ->main opsonizing antibody.
- IgG and IgM ->activate complement.
- IgA ->interferes with attachment to mucosa.
Hypersensitivity in infectious diseases. Serum sickness.
 Hypersensitivity
♦ Is a term used to describe when an immune response results in an exaggerated/inappropriate
reaction which is harmful to the host.
♦ It occurs on contact with a specific antigen which the individual is hypersensitive to (specific to
all people).
♦ The first contact the person has with the antigen will sensitize the individual ->induce
antibodies. The second contact with antigen will result in an allergic response.
♦ The hypersensitivity reactions can be divided into 4 main types:
- Type I - Immediate (Anaphylactic) Hypersensitivity (mediated by IgE)
- Type II - Cytotoxic Hypersensitivity (mediated by IgG)
- Type III - Immune-Complex Hypersensitivity (mediated by IgG) ->discussed in this title.
- Type IV - Delayed (Cell-Mediated) Hypersensitivity.
Immune complex-mediated (Type III) hypersensitivity
Is characterized by the formation of immune antigen-antibody complexes that accumulate in various
tissues. Under normal circumstances, monocytes remove these immune complexes, but in the presence of
excess antigen, they overwhelm the body's ability to clear them. The accumulation of these complexes
activates the complement cascade and leads to undesirable inflammation and damage to the surrounding
tissue. Accumulation of type III hypersensitivity complexes is most commonly observed in the kidneys,
blood vessels, joints and skin.
Three types of diseases can lead to immune complex hypersensitivity:
1. Chronic infection with a virus, bacteria or protozoa, along with a weak antibody response, will
eventually lead to the deposition of immune complexes and trigger this allergic response.
2. A second type of this condition stems from antibody raised against self-antigens. Since the antigens
are not removed in this case, immune complexes are constantly being formed and this is one of the
major damaging side effects of autoimmune disease such as systemic lupus erythematosus and
rheumatoid arthritis.

3. Third, constant chronic exposure to a particular antigen at a body surface can cause type III
hypersensitivity reactions. Farmer's lung is an example of this type of disease ->repeated exposure
to fungal spores present in moldy hay elicits an immune response and results in the formation of IgG
antibody directed against the spores. Subsequent exposure causes the formation of IgG-spore
immune complexes that accumulate in the alveoli of the lungs and cause inflammation leading to
lung tissue damage.
Immune complex diseases:
1. Glomerulonephritis (Acute
Poststreptococcal
Glomerulonephritis)
- It occurs
several weeks after a group A-beta
hemolytic streptococcal infection (especially of the skin).
- The compliment level will be low, which suggests an antigen-antibody reaction.
2. Rheumatoid Arthritis
- Is a chronic inflammatory autoimmune disease of joist, seen mainly in young women.
- Serum and synovial fluids contain “rheumatoid factors” = the IgM and IgG antibodies
that bind to Fc fragments of normal human IgG.
- The deposition of the immune complexes on synovial membrane and in blood vessels
will activate complement and attract polymorphonuclear cells, causing inflammation.
3. Systemic Lupus Erythematosus (SLE)
- Is a chronic inflammatory autoimmune disease that affects several organs, especially
skin of face, joints and kidneys.
- Antibodies are formed against DNA and other components of the nucleus of cells. These
antibodies will form immune complexes ->activate complement.
- Complement activation produces C5a which will attract neutrophils ->releases enzymes
->damages tissue.
 Serum Sickness
♦ Is a systemic inflammatory response to the presence of immune complexes that are deposited all
over the body.
♦ After a foreign serum or a certain drug has been injected into the body antigens start to slowly be
excreted -during this time antibody production starts ->the antibodies and antigens form
complexes ->start circulating and get deposited at different sites in the body.
♦ Symptoms start occurring few days to a couple of weeks after the injection of the serum/drug and
typically include:
- Fever
- Urticaria (skin hives)
- Arthralgia (joint pain)
- Lymphadenopathy
- Splenomegaly
- Eosinophilia
♦ Even though it takes several days for the symptoms to appear, serum sickness is classified as an
immediate reaction because symptoms occur right after immune complexes are formed!
♦ Symptoms get better as the immune system starts to remove the antigens and disappear
completely once the antigens are cleared from the system.
♦ These days serum sickness is caused more often by drugs like penicillin than by foreign serum,
since it is no longer frequently used.
Active and passive immunization, principles, side effects and complications.
 Bacterial diseases can be prevented by immunization that induces either passive or active immunity.
 Immunization is the process by which an individual is exposed to an agent that is designed to
upgrade his/her immune system against a specific agent, the agent is known as an immunogen.
 Immunization is the same as inoculation and vaccination, in that they both use a viable infective
agent as immunization does.
 When the human immune system is exposed to a disease once, it can develop the ability to quickly
respond to a second infection by the same agent. Therefore, by exposing an individual to an
immunogen in a controlled way, their body will be able to protect itself later on in life.

 Active immunity
This refers to immunity produced by the body following exposure to antigens.
♦ Naturally acquired active immunity
Exposure to different pathogens leads to sub-clinical or clinical infections which result in a
protective immune response against these pathogens.
♦ Artificially acquired active immunity
Immunization may be achieved by administering live or dead bacteria or their components.
Vaccines used for active immunization consist of:
1. Live, attenuated vaccine
2. Killed, bacterial vaccine
3. Toxoid vaccine (inactive protein exotoxins)
4. Subunit vaccines (capsular polysaccharide or purified protein)
1. Live, attenuated vaccine
The only example of live bacterial vaccine is one against tuberculosis (Mycobacterium Bovis:
BCG).
- Advantages: -
 Induces not only serum antibodies, but also cellular immunity and local IgA antibodies.
 Some may be applied orally.
 Usually few doses are needed
- Disadvantages:
 Attenuated strains may revert to virulent in rare cases.
 They may cause disease in immunosupressed patients.
 Live attenuated microbes are usually heat sensitive and must be refrigerated
2. Killed, bacterial vaccine
Most bacterial vaccines are killed organisms:
- Typhoid
- Cholera
- Plague
- Pertussis etc;
3. Toxoid vaccine (inactive protein exotoxins)
Vaccines that contain capsular polysaccharides as immunogen are directed towards:
- Streptococcus Pneumoniae
- Haemophilus Influenzae
- Neisseria Meningitides
- Salmonella Typhi
4. Subunit vaccines (capsular polysaccharide or purified protein)
Two vaccines contain toxoids as immunogen, vaccine against:
- Diphteria
- Tetanus.
 A toxoid is an inactivated toxin that has lost its ability to cause disease but has kept its
immunogenecity.
 Passive immunity
Immunity can be acquired, without the immune system being challenged with an antigen. This is done by
transfer of serum or gamma-globulins from an immune donor to a non-immune individual. Alternatively,
immune cells from an immunized individual may be used to transfer immunity. Passive immunity may be
acquired naturally or artificially.
♦ Naturally acquired passive immunity
- Immunity is transferred from mother to fetus through placental transfer of IgG or colostral
transfer of IgA.
♦ Artificially acquired passive immunity
- Immunity is often artificially transferred by injection with gamma-globulins from other
individuals or gammaglobulin from an immune animal.
- Passive transfer of immunity with immune globulins or gamma-globulins is practiced in
numerous acute situations of infections (diphtheria, tetanus, etc.), poisoning (insects,
reptiles, botulism), and as a prophylactic measure (hypogammaglobulinemia).
- In these situations, gamma-globulins of human origin are preferable although specific
antibodies raised in other species are effective and used in some cases (poisoning,
diphtheria, tetanus, gas gangrene, botulism).
- While this form of immunization has the advantage of providing immediate protection,
heterologous gammaglobulins are effective for only a short duration and often result in
pathological complications (serum sickness) and anaphylaxis. Homologous
immunoglobulins carry the risk of transmitting hepatitis and HIV.

Bacterial vaccines.
 CAPSULAR POLYSACCHARIDE VACCINES.
1. Streptococcus Pneumonia vaccine.
♦ Contain capsular polysaccharides of the 23 most prevalent types.
♦ Mostly for elderly and patients with chronic disease e.g. diabetes and cirrhosis.
2. Neisseria Meningitidis vaccine.
♦ Contains capsular polysaccharides of the 4 most important types (A, C, W-135 and Y).
♦ Given when there is high risk of meningitis e.g. outbreaks, military personnel.
3. Haemophilus Influenzae vaccine.
♦ Contains type B polysaccharide conjugated to diphteria toxoid or other carrier proteins.
♦ Given to kids between ages 2-15 months to prevent meningitis.
4. Typhoid Fever vaccine.
♦ Contains capsular polysaccharide of Salmonella Typhi.
♦ Given to people living or traveling to areas where there is high risk of Typhoid fever and to
people who are in close contact with those who are chronic carriers.
 TOXOID VACCINES
1. Corynebacterium Diphteriae vaccine.
♦ Contains the toxoid (formaldehyde-treated-exotoxin).
♦ It is given to all children in 3 doses at 2, 3 and 6 months of age with booster given 1 year
later.
2. Clostridium Tetani vaccine.
♦ Contains tetanus toxoid.
♦ Given to everybody, both early in life and later as booster.
3. Bordetella Petrussis vaccine.
♦ Contains petrussis toxoid + other proteins as well.
 A and B are subunit vaccines!
 PURIFIED PROTEIN VACCINES.
1. Two Bordetella Petrussis vaccines.
♦ One acellular vaccine containing purified proteins and another vaccine containing whole
killed bacteria.
♦ The acellular one contains inactivated petrussis toxin (petrussis toxoid), filamentous
hemaglutinin and pertractin for full protection.
♦ Acellular vaccine is given to all kids as protection against whopping cough.
♦ It is given in combination with diphteria and tetanus toxoids.
2. Lyme disease vaccine.
♦ Contains purified outer surface proteins of Borrelia Burgdorferi as immunogen.
♦ Given to those living in areas where disease in endemic.
3. Bacillus Anthracis vaccine.
♦ Contains “protective antigen” purified from organism.
♦ Given to those whose occupations put them at danger.
 LIVE ATTENUATED BACTERIAL VACCINE.
1. Vaccine against Tuberculosis.
♦ Contains live attenuated Mycobacterium Bo vis called BCG.
♦ Given to kids in countries with high risk of exposure (e.g. Norway/Sweden).
2. Vaccine against Typhoid fever.
♦ Contains live attenuated Salmonella Typhi.
♦ Given to those traveling to where there is a risk of Typhoid fever and to those in close
contact of infected people or carriers.
♦ Typhoid fever also has a capsular vaccine.
3. Vaccine against Tularemia.
♦ Contain live attenuated Francisella Tularensis.
♦ Given to those who could get exposed due to their occupation.

 KILLED BACTERIAL VACCINE.
1. Vibrio Cholera vaccine.
♦ Given to people traveling to areas where Cholera is endemic.
2. Yersinia Pestis vaccine.
♦ Given to those at high risk of contracting plaque.
3. Typhus vaccine.
♦ Containing killed Rickettsia Ricketsii.
♦ Give to members of armed forces.
4. Q-fever vaccine.
♦ Contains killed Coxiella Burnetti.
♦ Given to those at high risk of being exposed to animals infected with the organism.
Diagnostic immune reactions in microbiology.
Immunological techniques are used in diagnosis of infectious diseases. They are based on detection of:
a) presence of infectious agent (antigen, Ag)
b) detection of antibodies (Ab)
This means the patient has developed a specific immune response to the infectious agent.
 Reactions between Ag and Ab are highly specific, meaning the Ag will react in a highly selective
matter with the corresponding Ab or sensitized lymphocytes, instead of just producing a large
number of antibodies.
 The diagnosis of infection is usually based on demonstrating an increasing antibody levels (titer).
 The first serum should be collected during the acute phase of illness and the second serum should
be taken ~2 weeks later.
 IgM always proves disease.
 IgG only proves disease in case of a 4x fold increase in titer!
 Precipitation
♦ Reaction of soluble antigens like microbial toxins with antibodies, if there are enough
complexes formed it will cause precipitation. There are 2 types of precipitations:
- Ring precipitation ->is observed in a test tube. If concentration of Ag and Ab is optimal,
then precipitation will appear.
- Precipitation in gel ^ gel diffusion test is used to demonstrate toxin production of
Corynebacterium Diphteriae (ELEK test).
♦ Quellung test is used for identification of S. Pneumoniae - the capsule antigen will react with
specific antibodies and this can be observed using a microscope.
 Complement Fixation Test
♦ Complement is an enzymatic system of serum proteins that is activated by many types of Ab-Ag
reactions (complexes). This activation is used to test for Ags or Abs. The test determines the
presence of absence of Abs in the serum that is capable of fixing complement. Some Abs don’t
fix to complement, so the results of the test should be interpreted in terms of presence/absence
of complement fixing Abs, rather than presence/absence Abs in general.
♦ A principle of competitive binding is important for understanding this test = labeled Ags
compete with unlabelled Ags for the binding sites on specific Abs.
♦ This stage can be visualized in 2 stages:
1) Test system:
- In this case the antigen is cardiolipin (lipid extract from beef).
- The patient’s serum is heated at 56C for 30 min to inactivate the complement, then male
guinea pig complement is added instead- the antigen and serum is mixed with the
complement. If the patient has antibodies for the specific disease then Ag-Ab complexes
will form and fix to the guinea pig complement.
2) Indicator system:
- A suspension of sheep RBC is added to the test system mixture to determine if unbound
complement is available.
- The sheep RBC are sensitized with anti-sheep RBC called Hemolysin (causes
destruction of RBC releasing hemoglobin).
♦ Results:
- Positive result = the patient has Abs to the disease ->the complement has been fixed in the
first test (test system) therefore there is no hemolysis in the indicator system.
- Negative results = patient does not have Abs ->meaning the complement has not been fixed
(they are “free”) -you will be able to see lysis in the indicator test.
- The test has allot of controls, to make sure the RBC don’t lyse spontaneously in absence of
complement and to make sure that the complement survives stage 1 in absence of Ag-Ab
reaction.

- Complements are most effectively fixed in Ab excess or when Ag and Ab are in proper
proportion to form maximum binding to each other. Ag excess tends to result in poor
fixation of complement.
- Complement fixation is often used to test for Syphilis (Treponema Pallidum).
 Agglutination
♦ Is similar to precipitation, except the antigen is not soluble, but particulate. There are 2 types:
1. Slide agglutination:
- For identification of different antigens of different bacteria:
 E. Coli (K and O antigen)
 Salmonella (O and H antigen)
 Shigella (O antigen)
- These are all tested for epidemiological purposes. One drop of specific antiserum is put onto
a slide and then bacterial colony is added - mixed well. If the test is positive you will the
agglutination (lumps formed).
- Co-agglutination test: for identifying beta-hemolytic streptococci.
2. Tube agglutination:
- Makes a 2 fold dilution of the patient’s serum (the specimen is the serum) - here the question
is if the patient has specific antibodies or not.
- The particular antigen (bacterium) is added and incubated at 37C - agglutination will be seen
in some tubes. The titer (the highest dilution), is that dilution of serum in which you can still
see agglutination (the concentration of serum in which agglutination is still possible).
- The tube agglutination test in some cases has special names, depending on the bacteria:
 Salmonella Typhi -> Gruber Widal reaction.
 Rickettsia Prowazeki -> Weil Felix reaction.
 Brucella -> Wright reaction.
 RIA (Radio Immuno Assay)
♦ Based on competition between radioactively labeled (known) and unlabelled (unknown)
antigens for specific antibodies.
♦ Complexes forming between antigen and antibody can be separated in a radioactive way.
♦ RIA is very sensitive (nanograms/ml) method applied to the assay of hormones or drugs in
serum - the concentration of specific Ag in the unknown sample ca be determines.
♦ Disadvantage: radioactivity is dangerous.
 Allergic Skin Test
♦ Based on Type IV (delayed type) Hypersensitivity.
♦ The bacterium itself or its proteins (e.g. PPD of Mycobacterium) are inoculated intracellularly
and the reaction is checked 48-72 hours later.
♦ In positive reaction there will be erythema and edema.
♦ This test is performed for:
- Leprosy
- Tuberculosis (Mantoux test)
- Brucellosis
- Tularemia
- Psittacosis
- Lymphogranuloma Venerum
 Toxic Skin Test
♦ Used to demonstrate sensitivity or protection against exotoxins.
♦ Diluted toxins are inoculated intracellularly. If patient has antibodies (protected) there will be no
reaction (because the Abs neutralizes the toxin). However, if the patient is sensitive (no
antibodies) it will result in a positive result ->erythema of skin.
♦ This test is performed for:
- Streptococcus Pyogenes - Dick test.
- Corynebacterium Diphteria - Shick test.
 Immunofluorescence
♦ Fluorescent dyes can be attached to antibodies and then observed by UV-light in fluorescent
microscope. The labeled antibodies can be used to identify antigens on the surface of bacteria or
in cells in histological specimens.
♦ There are 2 ways of performing the test:
1. Direct :
- This is when known labeled antibody interacts with unknown antigen (indirectly).
2. Indirect:
- A known antigen is attached to a slide and the patient’s serum with unknown serum
antibodies is added. If the serum antibodies react with the antigen, they will remain fixed to
the slide even after washing and can then be detected by adding a fluorescent-labeled
antiglobulin (second antibody).
- This test is more sensitive than the direct test because more than one labeled antibody
adheres per antigenic site.
- The method is widely used to rapid identification of bacteria and viruses.
 Sandwich Technique
♦ Used to identify antibodies in tissue.
♦ Known antigen is added to the tissue and is then abound by a specific (unknown) antibody
present in the tissue.
♦ Specific fluorescent-labeled antibody (known) is added which reacts with the fixed antigen.

 Flow Cytometry (FAC - Fluorescent Activated Cell Sorter)
♦ It analyzes a single cell suspension flowing through a set of laser beams in order to measure the
relative amount of light scattered by microscopic particles (giving info about relative size and
granularity) and the relative fluorescent of the particles.
♦ For a mixture of white blood cells, it is easy to separate the cells into major classes e.g. small
lymphocytes separated from granulocytes which are larger and contain more granules (scatter
more light).
♦ This technique is used in clinical medicine and biochemical research.
 ELISA (Enzyme Linked Immuno Sorbent Assay).
♦ In order to measure antibodies, known antigens are fixed to a solid phase (plastic microdilution
plate), incubated with test serum dilution, washed and reincubated with anti-immunoglobulin
labeled with an enzyme (e.g. horse radish peroxidase).
♦ Enzyme activity, measured by adding the specific substrate and measuring the color reaction, is
a direct function of the amount of antibody bound.
 Western Blot aka Immunoblotting.
♦ It is used to identify a particular antigen in a complex mix of proteins.
♦ The mix of proteins is subjected to sodium dodecyl sulfate (SDS) polyacrylamide gel
electrophoresis. This separates the proteins according to molecular size. The proteins are
transferred to a filter (microcellulose) so that the position of the elected proteins corresponds to
their position in the gel. The filter reacts with a specific antibody, which binds only to epitopes
of the proteins. The Ag-Ab complex can be detected by an enzymatic reaction or by
radiolabeled reaction.
♦ Western Blot is useful for confirmation of HIV-1 virus seropositivity. (First always test with
ELSA, if it is positive, then check again with Western Blot).

STAPHYLOCOCCUS AUREUS INFECTIONS
STAPHYLOCOCCUS
Characteristics gram + (stains blue with gram
stain)
coccus (small, round
cell)
grow in grape-like cell
clusters
non-motile (has no
flagellae)
non-spore forming (does not form a sturdy
vegetative
infectious
particle)
facultative anaerobic (may survive in both oxygen-rich
andoxygen-poor environments)
Grow on no enriched
media
Moderately sized white
or golden colonies
Commensals on skin and
mucous membranes
Comparatively stable in
environment
Cause pyrogenic
infections
COAGULASE + STAPHYLOCOCCI
Staphylococcus Aureus
Characteristics non-
encapsulated
beta-hemolytic (completely lyses RBCs on blood
agar,
forms a clear halo around it's colonies on blood
agar)
opportunistic
pathogen
Reservoirs humans (normal flora of the skin, nasopharynx,
oropharynx
and female
genitalia)
animals (primarily
cattle)
Transmission directcontact("person-to-
person")
perinatal("mother-to-
child")
zoonotic ("animal-to-
human")
contaminated
food
Toxins staphylococcal enterotoxin (causes secretion of
histamine from mast cells " peristalsis " food

poisoning,
exfoliatin (disrupts
desmosomes of skin epithelium "
scalded skin syndrome, see
below)
toxic shock syndrome toxin-1
("TSST-1", causes massive
activation of helper T-cells " massive IL-2
secretion "
staphylococcal toxic shock syndrome
Diseases
most
common cause of skin infections (folliculitis,
cellulitisand impetigo), skin abscesses (pustules,
furuncles,
carbuncles), and wound infections
(together with
Streptococcus Pyogenes)
most common cause of acute infections
endocarditis
bronchopneumonia and pulmonary
abscesses
cystitis and renal abscesses (primarily if urinary
catheter)
meningitis and cerebral
abscesses
infective arthritis (primarily occurs in children and
elderly)
and osteomyelitis (primarily occurs in male
children)
septicemia (primarily if central venous
catheter)
Food
Poisoning
most common cause of food poisoning
gastroenteritis (abdominal pain, vomiting and watery
diarrhea)
spontaneously resolves in < 24 hours
caused by Staphylococcus Aureus contamination of food "
production and secretion of staphylococcal enterotoxin (see
above) " ingestion of staphylococcal enterotoxin-
containing
food may progress to
staphylococcal toxic
shock syndrome

Scalded Skin Syndrome
epidermal skin shedding
primarily occurs around the umbilicus of neonates
caused by Staphylococcus Aureus infection of skin "
production and secretion of exfoliatin (see above)
may progress to staphylococcal toxic shock syndrome
Staphylococcal Toxic Shock Syndrome
- "STSS"
high fever, vomiting and watery diarrhea " diffuse
erythematous rash and focal epidermal skin shedding "
hypotension
may lead to septic shock " death
primarily occurs in menstruating females using tampons
caused by Staphylococcus Aureus septicemia " production
and secretion of TSST-1
Treatment beta-lactamase resistant penicillins
vancomycin (if resistant ot beta-lactamase resistant
penicillins, "methicillin-resistant staphylococcus aureus",
"MRSA")

COAGULASE NEGATIVE STAPHYLOCOCCI
COAGULASE - STAPHYLOCOCCI
Staphylococcus Epidermidis
Characteristics - encapsulated
- gamma-hemolytic (does not lyse RBCs on blood agar)
- opportunistic pathogen
Reservoirs - humans (only reservoir, normal flora of the skin,
nasopharynx, oropharynx and GI tract)
Transmission - direct contact
Toxins - none in particular
Diseases Nosocomial Infections
- cystitis (primarily if urinary catheter)
- subacute infectious endocarditis (primarily if prosthetic
heart valves)
- infective arthritis (primarily if prosthetic joints)
- septicemia (primarily if central venous catheter)
Treatment - vancomycin
- trimethoprim-sulfamethoxazole
Staphylococcus Saprophyticus
Characteristics - non-encapsulated
- gamma-hemolytic
- obligate pathogen
Reservoirs - humans (only reservoir, not normal flora)
Diseases - second most common cause of cystitis (after Escherichia
Coli, see 18, primarily occurs in sexually active females)
Treatment - broad spectrum penicillins

STREPTOCOCCUS PYOGENES: PYOGENIC INFECTIONS
STREPTOCOCCUS PYOGENES: SCARLET FEVER AND
SECONDARY STREPTOCOCCAL DISEASES
STREPTOCOCCUS
Characteristics - gram +
- coccus
- grow in chains or in pairs
("diplococci"/”streptococci”)
- non-motile
- non-spore forming
- facultative anaerobic
- classified according to the structure of the C carbohydrate in their
respective cell walls ("lancefield antigen") as well as their
respective hemolytic abilities
Fastidious, require enriched
media
Catalase negative
Commensals on mucous
membranes
Cause pyrogenic infections
Streptococcus Pyogenes
- lancefield group A antigen ("group A Streptococcus")
- beta-hemolytic
- obligate pathogen
- droplet nuclei("respiratory spray")
Toxins - pyrogenic exotoxin ("erythrogenic exotoxin", causes scarlet fever
and streptococcal toxic shock-like syndrome, see below)
Diseases Invasive Diseases
- most common cause of skin infections (folliculitis, cellulitis and
impetigo), skin abscesses (pustules, furuncles, carbuncles), and
wound infections (together with Staphylococcus Aureus, see 1)
- most common BACTERIAL cause of acute pharyngitis ("acute
tonsillitis", "strep throat")
- otitis media and mastoiditis
- subacute infectious endocarditis
- septicemia
Cross Reactive Diseases
- rheumatic fever
- acute post-streptococcal glomerulonephritis ("diffuse proliferative
glomerulonephritis")
Scarlet Fever

- high fever and diffuse, brightly erythematous ("scarlet-red") rash
beginning on the trunk and neck and then progressing to the
extremities " shedding of the affected skin
- caused by Streptococcus Pyogenes septicemia " production and
secretion of pyrogenic exotoxin (see above)
- may progress to streptococcal toxic shock-like syndrome (see
below)
Streptococcal Toxic Shock-Like Syndrome
- "STLS"
- analogous to staphylococcal toxic shock syndrome (see 1)
- caused by Streptococcus Pyogenes septicemia " production and
secretion of pyrogenic exotoxin (see above)
Treatment - narrow spectrum penicillins
- beta-lactamase resistant penicillins (if skin infections, due to the
possibility that the skin infections might be of Staphylococcus
Aureus origin, see 1)

STREPTOCOCCUS PNEUMONIAE
Streptococcus Pneumoniae ("Pneumococcus")
- no lancefield antigen
- alpha-hemolytic (partially lyses RBCs on blood agar, forms a
greenish halo around it's colonies on blood agar)
Reservoirs - humans (only reservoir, normal flora of the nasopharynx,
oropharynx and conjunctiva)
- droplet nuclei
- contaminated fomites (indigestible objects)
Diseases - most common cause of lobar pneumonia and pulmonary abscesses
- most common cause of meningitis and cerebral abscesses
- most common cause of otitis media (primarily occurs in children)
- sinusitis
- subacute infectious endocarditis and acute pericarditis
- septicemia
- macrolides

THE "STREPTOCOCCUS VIRIDANS" GROUP, THEIR ROLE
IN CARIOGENESIS
ENDOCARDITIS LENTA AND ITS BACTERIAL DIAGNOSIS
Streptococcus Viridans
Species - S. Mutans
- S. Intermedius
- S. Salivarius
- no lancefield antigen
- alpha-hemolytic
Reservoirs - humans (only reservoir, normal flora of the skin, nasopharynx,
oropharynx and oral cavity)
Transmission - perinatal
Diseases - most common cause of dental caries (primarily caused by S.
Mutans)
- most common cause of subacute infectious endocarditis
("endocarditis lenta", caused by all species of Streptococcus
Viridans)
- cerebral abscesses and hepatic abscesses (primarily caused by S.
Intermedius)
- septicemia (caused by all species of Streptococcus Viridans)
- broad spectrum penicillins in conjunction with aminoglycosides (if
subacute infectious endocarditis, due to the possibility that the
subacute infectious endocarditis might be of enterococcus faecialis
origin, )

STREPTOCOCCUS AGALACTIAE, ENTEROCOCCUS
FAECIALIS
Streptococcus Agalactiae
- lancefield group B antigen ("group B Streptococcus")
- beta-hemolytic
Reservoirs - humans (normal flora of the GI tract and female genitalia)
- animals
Transmission - perinatal
Diseases - most common cause of neonatal pneumonia
- most common cause of neonatal meningitis
- cystitis and endometritis
- endocarditis and peritonitis
- infective arthritis and osteomyelitis
- septicemia
- aminoglycosides (if neonatal meningitis, due to the possibility that
the neonatal meningitis might be of Escherichia Coli origin,
-

Streptococcus Faecalis ("Enterococcus Faecalis")
- lancefield group D antigen ("group D Streptococcus")
- alpha-hemolytic
- facultative alkaliphilic (may survive in both both neutral- and
alkaline environments, thus may grow in bile)
Reservoirs - humans (normal flora of the GI tract)
- animals
Transmission - trauma
Diseases - second most common cause of subacute infectious endocarditis
(after Streptococcus Viridans, see 7)
- wound infections
- cholecystitis (due to it's facultative alkaliphilic nature, see above)
- cystitis
- septicemia
Treatment - broad spectrum penicillins in conjunction with aminoglycosides
(due to high antibiotic resistance)
- vancomycin (if resistant to broad spectrum penicillins and/or
aminoglycosides)

PEPTOCOCCUS AND PEPTOSTREPTOCOCCUS
PEPTOCOCCUS
Species - P. Niger (all other species that previously were part of the Peptococcus
genus are now part of the Peptostreptococcus genus, see below)
Characteristics - gram +
- coccus
- grow in chains or in pairs
- non-encapsulated
- non-motile
- non-spore forming
- gamma-hemolytic
Reservoirs - humans (normal flora of the nasopharynx, oropharynx, GI tract and female
genitalia)
- animals
- soil
Transmission - trauma
Diseases - wound infections (primarily if surgical)
- sinusitis
- bronchopneumonia and pulmonary abscesses
- appendicitis, peritonitis and hepatic abscesses
- cystitis
- vulvovaginitis and pelvic inflammatory disease ("PID", endometritis,
salpingitis and oophitis)
- meningitis and cerebral abscesses
- septicemia
- clindamycin

PEPTOSTREPTOCOCCUS
Species - P. Aerobius
- P. Magnus
- P. Micros
Characteristics - same characteristics, reservoirs, transmission, toxins, diseases and
treatment as Peptococcus (see above, Peptostreptococcus only differs from
Peptococcus in it's genome and the amino acid sequence of it's proteins)

NEISSERIA GONORRHOEAE
NEISSERIA
Characteristics - gram - (does not stain with gram stain, but stains red with gram
contrastain)
- curved coccus
- grow in pairs
- non-motile
- non-spore forming
- facultative intracellular (may survive both extracellularly and
intracellularly)
Neisseria Gonorrhoeae ("Gonococcus")
- obligate pathogen
Transmission - sexual( "sexually transmitted disease", "STD","venereal disease")
- perinatal
Toxins - lipooligosaccaride ("LOS", analogous to LPS, )
Diseases In Males
- gonorrheal urethritis ("gonorrhea")
- prostatitis and epididymitis
In Females
- gonorrheal urethritis and cervicitis ("gonorrhea")
- pelvic inflammatory disease (see 9), tuboovarian abscesses, ectopic
pregnancies and infertility
In Both Males and Females
- pharyngitis (primarily if oral intercourse)
- proctitis (primarily if anal intercourse)
- meningitis and subacute infectious endocarditis
- dermatitis in conjunction with infective arthritis ("dermatitis-
arthritis syndrome")
- septicemia
In Neonates
- conjunctivitis and blindness
Treatment - third generation cephalosporins
-

- third generation cephalosporins in conjunction with tetracyclines
(if gonorrheal urethritis and/or cervicitis, due to the possibility that
the urethritis and/or cervicitis may be of Chlamydia Trachomatis
or Ureaplasma Urealyticum origin)
NEISSERIA MENINGITIDIS
Neisseria Meningitidis ("Meningococcus")
Reservoirs - humans (only reservoir, normal flora of the nasopharynx)
- droplet nuclei
Toxins - LOS
Diseases Meningococcemia
- spiking fever, diffuse petechial skin rashes and infective arthritis
- caused by Neisseria Meningitidis septicemia
- may progress to meningitis and/or waterhouse-friderichsen
syndrome (see below)
Meningitis
- intense headache, vomiting and stiff neck " delirium " coma
- permanent central neuropathies upon recovery
- caused by progression of meningococcemia (see above)
Waterhouse-Friderichsen Syndrome
- "fulminant meningococcemia"
- DIC " severe bilateral adrenal hemorrhage " adrenal crisis
- > 50% mortality if untreated (within 6-8 hours (!))
- caused by progression of meningococcemia (see above)
- third generation cephalosporins

ENTEROPATHOGENIC (EPEC), ENTEROTOXIGENIC (ETEC)
AND ENTEROHEMORRHAGIC (EHEC) ESCHERICHIA COLI
ESCHERICHIA
Characteristics - gram -
- rod (thin, elongated cell)
- encapsulated
- motile (has flagellae)
- non-spore forming
Escherichia Coli
Characteristics - opportunistic pathogen
- animals
- fecal-oral
- contaminated water
- contaminated food
- contaminated fomites
Enteropathogenic Escherichia Coli ("EPEC")
Characteristics - gamma-hemolytic
Toxins - lipopolysaccaride ("LPS", "endotoxin")
Diseases - watery diarrhea (primarily occurs in infants)
Treatment - oral fluid and electrolyte replacement

Enterotoxigenic Escherichia Coli ("ETEC")
Toxins - heat-labile enterotoxin ("LT", inhibits the GTPase domain
of adenylate cyclase " ! cAMP " ! Cl- and HCO3-
secretion " ! intraluminal osmotic pressure " osmotic
diarrhea (see below), analogous to choleragen (see 23))
- heat-stabile enterotoxin ("ST", inhibits the GTPase domain
of guanylate cyclase " ! cGMP " same effect as LT, see
above)
- LPS
Diseases - most common BACTERIAL cause of gastroenteritis
("traveler'sdiarrhea","montezuma's revenge",see 1,
primarily occurs in travelers)
Enterohemorrhagic Escherichia Coli ("EHEC")
Toxins - verotoxin ("shiga-like toxin", "SLT", inhibits the 60S
ribosomal subunit " # protein synthesis " necrosis and
inflammation " hemorrhagic colitis and hemolytic uremic
syndrome (see below), analogous to shiga toxin (see 13))
- LPS
Diseases Hemorrhagic Colitis
- low-grade fever, abdominal cramps, abdominal pain,
vomiting and purulent hemorrhagic diarrhea
- spontaneously resolves in < 1 week
- caused by EHEC infection of the GI tract " production and
secretion of verotoxin (see above) " necrosis of the
enterocytes
- may progress to hemolytic-uremic syndrome (see below)
Hemolytic-Uremic Syndrome
- "HUS"
- thrombosis and following thrombocytopenia "
sequestration of RBCs passing through the thrombi and
following hemolytic anemia " occlusion of the glomeruli
by the thrombi and following intrarenal azotemia and
uremia
- most common cause of hemolytic-uremic syndrome
- caused by verotoxin (see above) toxemia " necrosis of the
glomerular endothelial cells

Treatment - oral fluid and electrolyte replacement (if hemorrhagic
colitis)
- careful oral fluid and electrolyte replacement (if hemolytic-
-uremic syndrome, due to occlusion of the glomeruli, -
Uropathogenic Escherichia Coli ("UPEC")
Uropathogenic Escherichia Coli ("UPEC")
Characteristics - beta-hemolytic
Toxins - cytotoxic necrosis factor ("CNF", causes necrosis of the
transitional epithelial cells of the urinary tract " cystitis
and/or pyelonephritis, see below)
- LPS
Diseases - most common cause of cystitis (primarily occurs in sexually
active females) and pyelonephritis
Treatment - fluoroquinolones

Meningitis-Associated Escherichia Coli ("MNEC")
meningeal endothelial cells " neonatal meningitis, see
below)
- LPS
Diseases - second most common cause of neonatal meningitis (after
Streptococcus Agalactiae,
- most common cause of septicemia
Treatment - aminoglycosides (if neonatal meningitis, due to the
possibility that the neonatal meningitis might be of
Streptococcus Agalactiae origin,
- fluoroquinolones (if septicemia)

BACILLARY DYSENTERY
SHIGELLA
Species - S. Dysenteriae
- S. Flexneri
- S. Boydii
- rod
- non-encapsulated
- non-motile
- non-spore forming
- facultative intracellular
- obligate pathogen
- fecal-oral
- vectorial (flies)
- contaminated food
Toxins - shiga toxin (analogous to verotoxin (see 12), causes hemorrhagic
bacillary dysentery and hemolytic-uremic syndrome (see below))
- LPS
Diseases Bacillary Dysentery
- low-grade fever, abdominal cramps, abdominal pain, vomiting and
purulent hemorrhagic diarrhea
- primarily occurs in children and elderly
- analogous to hemorrhagic colitis
- caused by Shigella infection of the GI tract " production and
secretion of shiga toxin (see above) " necrosis of the enterocytes
Hemolytic-Uremic Syndrome
- see 12
Treatment - broad spectrum penicillins in conjunction with oral fluid and
electrolyte replacement (if bacillary dysentery)
- broad spectrum penicillins in conjunction with careful oral fluid
and electrolyte replacement (if hemolytic-uremic syndrome, due to
occlusion of the glomeruli,

SALMONELLAE CAUSING ENTERIC FEVER
SALMONELLA
- rod
- encapsulated
- motile
- non-spore forming
- facultative alkaliphilic
Salmonella Typhi
Characteristics - obligate pathogen
- fecal-oral
- contaminated food
Toxins - LPS
Diseases Typhoid Fever
- "enteric fever"
- enterocolitis (high fever, headache, abdominal pain, vomiting and
watery diarrhea) and mesenteric lymphadenitis ("mock
appendicitis") " abdominal rash ("rose spots"),
hepatosplenomegaly and generalized lymphadenomegaly
- caused by phagocytosis of Salmonella Typhi by macrophages of
the gut-associated lymphoid tissue ("GALT") " survival of
Salmonella Typhi within the macrophages " dissemination of
Salmonella Typhi in virtually every lymphoid organ
- third generation cephalosporins

SALMONELLA GASTROENTERITIS
Salmonella Enteritidis
Reservoirs - humans (not normal flora)
- animals (primarily cattle and poultry)
- fecal-oral
- zoonotic
- contaminated food (primarily meat, milk and eggs)
Toxins - LPS
Diseases Salmonellosis
- gastroenteritis (see 1)
- caused by Salmonella Enteritidis infection of the GI tract

YERSINIA ENTEROCOLITICA AND YERSINIA
PSEUDOTUBERCULOSIS
YERSINIA
- bipolar (the extremities take up more stain than the center) rod
- non-spore forming
Yersinia Enterocolitica
Characteristics - motile
- non-encapsulated
- obligate pathogen
- animals (primarily swine, cattle and birds)
- fecal-oral
- zoonotic
- contaminated food (primarily meat and milk)
Toxins - yersinial enterotoxin (analogous to ST causes
enterocolitis (see below))
- LPS
Diseases - enterocolitis primarily occurs in children and in
immunocompromised) and mesenteric lymphadenitis ("mock
appendicitis")
- cellulitis, iritis and pharyngitis
- septicemia
Treatment - oral water and electrolyte replacement (if enterocolitis)
- third generation cephalosporins (if septicemia)
--

Yersinia Pseudotuberculosis
Characteristics - same characteristics, reservoirs, transmission, diseases and
treatment as Yersinia Enterocolitica (see above, only differs in
toxins secreted, see below)
- (also causes a disseminated tuberculosis-like syndrome in animals,
thus "Pseudotuberculosis")
enterocytes of the small intestine " enterocolitis, see above)
- LPS
continued in 17
-

YERSINIA PESTIS
Yersinia Pestis
- non-motile
- obligate pathogen
Reservoirs - humans (only in epidemic periods, not normal flora)
- animals (primarily rats and other rodents)
Transmission - droplet nuclei (only in epidemic periods)
- zoonotic
- vectorial (fleas)
Toxins - LPS
Diseases The Bubonic Plague
- "the black death"
- fever and severe focal lymphadenomegaly ("buboae")
- caused by phagocytosis of Yersinia Pestis by macrophages "
dissemination of Yersinia Pestis in regional lymph nodes
- may progress to the septic plague (see below)
The Septicemic Plague
- large black gangrenous hemorrhages of the skin, meninges, GI
tract and genitourinary tract
- > 50% mortality if untreated (within 3-6 days (!))
- caused by Yersinia Pestis septicemia
- may progress to the pneumonic plague (see below)
The Pneumonic Plague
- pneumonia and severe black gangrenous hemorrhages of the lungs
- > 75% mortality if untreated (within 2-4 days (!))
- caused by secondary septicemic spread of Yersinia Pestis to the
respiratory tract or by primary inhalation of droplet nuclei (only in
epidemic periods)
Treatment - aminoglycosides
- tetracyclines

PROTEUS, PROVIDENCIA
PROTEUS
Species - P. Mirabilis
- P. Vulgaris
- P. Penneri
- rod
- motile
- non-spore forming
- non-encapsulated
- water
- soil
Transmission - fecal-oral
- direct contact
Toxins - LPS
Diseases - wound infections
- bronchopneumonia
- cystitis and urolithiasis
- septicemia
Treatment - cephalosporins
- aminoglycosides
-

PROVIDENCIA
Species - P. Stuartii
- P. Rettgeri
- P. Alcalifaciens
Characteristics - same characteristics, reservoirs, transmission and toxins as Proteus
(see above, only differs in diseases and treatment, see below)
Diseases - gastroenteritis (see 1, primarily occurs in travelers)
- wound infections (primarily if burned)
- bronchopneumonia (primarily if intubated)
- cystitis (primarily if urinary catheter) and urolithiasis
- septicemia
Treatment - fluoroquinolones
- tetracyclines

KLEBSIELLA, ENTEROBACTER, CITROBACTER
KLEBSIELLA
Species - K. Pneumoniae
- K. Rhinoscleromatis
- K. Ozeanae
- rod
- encapsulated
- non-motile
- non-spore forming
Reservoirs - humans (normal flora of the skin, nasopharynx, oropharynx and GI
tract)
- animals
- water
- soil
- fecal-oral
Toxins - LPS
Diseases - second most common cause of lobar pneumonia and pulmonary
abscesses (after Streptococcus Pneumoniae, see 5, primarily caused
by K. Pneumoniae)
- rhinoscleroma (granulomas of both the upper and lower respiratory
tract " airway obstruction, primarily caused by K.
Rhinoscleromatis)
- ozena (atrophic rhinitis in conjunction with chronic sinusitis,
primarily caused by K. Ozaenae)
- wound infections (primarily if burned, caused by all species of
Klebsiella)
- cystitis (primarily if urinary catheter, caused by all species of
Klebsiella)
- second most common cause of septicemia
caused by all species of Klebsiella)
- fluoroquinolones

ENTEROBACTER
Species - E. Aerogenes
- E. Agglomerans
- E. Cloacae
- rod
- encapsulated
- motile
- non-spore forming
- animals
- water
- soil
- fecal-oral
Toxins - LPS
- skin infections (folliculitis, cellulitis and impetigo), skin abscesses
(pustules, furuncles, carbuncles), and wound infections
- bronchopneumonia and pulmonary abscesses
- cystitis and renal abscesses (primarily if urinary catheter)
- neonatal meningitis and cerebral abscesses
- osteomyelitis and arthritis
- septicemia
- tetracyclines

CITROBACTER
Species - C. Diversus
- C. Freundii
- C. Amalonaticus
- rod
- encapsulated
- motile
- non-spore forming
- animals
- water
- direct contact
- perinatal
- contaminated food
Toxins - LPS
Diseases - neonatal meningitis and cerebral abscesses (caused primarily by C.
Diversus)
- cystitis and renal abscesses (especially if urinary catheter, caused
by all species of Citrobacter)
- septicemia (caused by all species of Citrobacter)
- chloramphenicol

CAMPYLOBACTER, HELICOBACTER
CAMPYLOBACTER
- helical rod
- motile
- non-spore forming
- non-encapsulated
- aerobic and microaerophilic (may survive in relatively oxygen-
poor environments)
Campylobacter Jejuni
- animals (primarily cattle and poultry)
- direct contact
- zoonotic
- contaminated food (primarily meat and milk)
Toxins - campylobacteral enterotoxin (analogous to choleragen (see 23),
causes gastroenteritis (see below))
- cytolethal distending toxin ("CDT", DNase,causes double-
stranded DNA-breaks " necrosis and inflammation "
hemorrhagic colitis and hemolytic-uremic syndrome, see below)
- LPS
Diseases In Children
- second most common BACTERIAL cause of gastroenteritis (see 1,
after ETEC, see 12)
- hemorrhagic colitis and hemolytic-uremic syndrome
- septicemia
Treatment - oral water and electrolyte replacement (if gastroenteritis and/or
hemorrhagic colitis)
- aminoglycosides (if hemolytic-uremic syndrome and/or
septicemia)
-

Campylobacter Fetus
- animals (primarily cattle, sheep and goats)
- fecal-oral
- zoonotic
- contaminated food
Toxins - LPS
Diseases In Immunocompromized
- meningitis, pleuritis, pericarditis and synovitis
- septicemia
- macrolides
HELICOBACTER
- helical rod
- motile
- non-spore forming
- non-encapsulated
- aerobic and microaerophilic

Helicobacter Pylori
- animals (primarily cats)
- zoonotic
Toxins - vacuolating cytotoxin A ("VacA", causes chronic atrophic gastritis,
gastric adenocarcinoma and MALToma, see below)
- LPS
Diseases - most common cause of duodenal ulcers
- second most common cause of gastric ulcers (after aspirin)
- acute erosive gastritis
- chronic atrophic gastritis
- gastric adenocarcinoma and MALToma
Treatment - hydrogen ion/potassium antiporter inhibitors (if duodenal ulcers,
gastric ulcers and/or acute erosive gastritis)
- metronidazole in conjunction with broad spectrum penicillins (if
chronic atrophic gastritis, gastric adenocarcinoma and/or
MALToma)

VIBRIO AND AEROMONAS
VIBRIO
- curved rod
- motile
- non-spore forming
- non-encapsulated
Vibrio Cholerae
Characteristics - obligate isotonic (may only survive in isotonic environments)
- obligate pathogen
- water
- contaminated food
Toxins - choleragen (analogous to LT causes cholera gravis (see
below))
- LPS
Diseases Cholera Gravis
- severe watery diarrhea (>25 liter per day)
- may lead to hypovolemia " hypovolemic shock
- > 50% mortality if untreated (within hours (!))
- caused by Cholera Gravis infection of the GI tract " production
and secretion of choleragen (see above)
Treatment - oral water and electrolyte replacement
- tetracyclines

Vibrio Parahaemolyticus
Characteristics - facultative hypertonic ("halophilic", may survive in both isotonic
and hypertonic environments, thus may survive in salt water)
- obligate pathogen
- water (both fresh and salt water)
- animals (primarily fish and crustaceans)
- contaminated food (primarily seafood)
Toxins - RTX toxin (causes gastroenteritis, hemorrhagic colitis and
hemolytic-uremic syndrome, see below)
- LPS
Diseases - wound infections
- gastroenteritis (see 1)
- hemorrhagic colitis and hemolytic-uremic syndrome
- septicemia
Treatment - oral water and elecrolyte replacement (if gastroenteritis,
hemorrhagic colitis and/or hemolytic-uremic syndrome)
- tetracyclines (if wound infections and/or septicemia)
AEROMONAS
- rod
- motile
- non-spore forming
- non-encapsulated
- facultative hypertonic
-35 -

Aeromonas Hydrophilia
- water (both fresh and salt water)
- soil
- contaminated soil
- contaminated food (primarily seafood)
Toxins - aeromonas heat-labile enterotoxin ("ALT", "cytotonic
enterotoxin", analogous to choleragen , causes
gastroenteritis (see below))
- LPS
Diseases - gastroenteritis (see 1)
- wound infections (primarily if leech bites)
- endophthalmitis, keratitis and corneal ulcers
- bronchopneumonia
- cystitis
- septicemia
Treatment - oral fluid and electrolyte replacement (if gastroenteritis)
- tetracyclines (if all other diseases)
-36 -

ACINETOBACTER
ACINETOBACTER
- pleomorphic rod (rod in log phase, coccobacillary rod (short
truncated rod) in stationary phase)
- encapsulated
- non-motile
- non-spore forming
- obligate aerobic
Acinetobacter Baumanii
Reservoirs - humans (normal flora of the skin)
- water
- soil
- droplet nuclei
- contaimanted soil
Toxins - LPS
- wound infections (primarily if surgical)
- bronchopneumonia (primarily if intubated)
- peritonitis (primarily if continuous ambulatory peritoneal dialysis)
- cystitis (primarily if urinary catheter)
- meningitis (primarily if external ventricular drainage catheter)
- septicemia
Treatment - carbapenems
- polymixins

PSEUDOMONAS AERUGINOSA
PSEUDOMONAS
- rod
- encapsulated
- motile
- non-spore forming
- obligate aerobic
Pseudomonas Aeruginosa
- water
- soil
- droplet nuclei
- contaimanted soil
Toxins - exotoxin A ("exoA", ribosylates elongation factor 2 " # protein
synthesis " necrosis and inflammation, analogous to diphtheria
toxin,
- LPS
Diseases In Healthy
- endophthalmitis, keratitis and corneal ulcers (primarily if contact
lenses)
- otitis externa ("swimmer's ear")
In Immunocompromized
- second most common cause of acute infectious endocarditis (after
Staphylococcus Aureus, see 1)
- wound infections (primarily if burned)
- tracheobronchitis and bronchopneumonia (primarily if intubated)
- chronic bronchopneumonia and severe progressive pulmonary
abscesses (primarily if cystic fibrosis)
- cystitis and pyelonephritis (primarily if catheterized)
- meningitis (primarily if external ventricular drainage catheter)
- septicemia
Treatment - extended spectrum penicillins in conjunction with aminoglycosides
(due to high antibiotic resistance)

HAEMOPHILUS INFLUENZAE, H. PARAINFLUENZAE
HAEMOPHILUS
- pleomorphic rod
- non-motile
- non-spore forming
Haemophilus Influenzae
Reservoirs - humans (only reservoir, normal flora of the nasopharynx,
oropharynx, oral cavity and conjunctiva)
Transmission - droplet nuclei
Toxins - LPS
Diseases In Neonates and Children
- acute laryngoepiglottitis ("obstructive laryngoepiglottitis")
- meningitis
- septicemia
- chloramphenicol
-39 -

Haemophilus Parainfluenzae
- same reservoirs, transmission and toxins as Hemophilus
Influenzae, see above)
Diseases In Teenagers and Adults
- sinusitis
- bronchopneumonia (primarily if viral interstitial pneumonitis
and/or chronic bronchitis is already present)
- septicemia
- broad spectrum penicillins in conjunction with beta-lactamase
inhibitors (if resistant to broad spectrum penicillins)

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