Basic Microbiology

BASIC MICROBIOLOGY http://crisbertcualteros.page.tl

RULES IN GRAM STAINING
Most cocci are Gram positive EXCEPT:
Neisseria
Moraxella
Veillonella
Spirochetes are a negative
Most bacilli are GRAM NEGATIVE except B 2 – Bacillus, Bifidobacterium A - Actinomyces N - Nocardia S - Streptomyces C 2 - Clostridium, Corynebacterium E - Erysipelothrix L 2 - Listeria, Lactobacillus

Actinomyces israelii

Bacteria Not Seen by Gram staining Giemsa or other tissue stain Intracellular, Very small Rickettsiae Inclusion bodies in cytoplasm Intracellular, very small Chlamydiae None No cell wall M. pneumoniae Darkfield micro/ Fluorescent micro Too thin to see Spirochetes Acid-fast stain High lipid in cell wall Mycobacteria Alternative Reason Name

ACID-FAST STAINING
Carbol fuchsin method
Ziehl-Neelsen Method
Kinyoun Method
C arbol fuchsin
A cid alcohol,
M ethylene blue/malachite green
Acid-fast: red
Non-acid-fast: blue or green
Fluorochrome method
Auramine/rhodamine
Acid-alcohol
K permanganate
Fluorescent microscope

Acid-fast organisms
Mycobacterium spp.
Nocardia spp. (partial)
Legionella micdadae
Cryptosporydium
Isospora

Genes can be transmitted between bacteria by each of the following processes/ except:
generalized transduction
conjugation
C. transversion
D. lysogenic conversion

Which of the following is responsible for the passage of low molecular weight solutes through the outer membrane of Gram negative bacteria?
Capsules
Endospores
Mesosomes
porins

Bacteria which are able to grow at temperature below 25 o C are called
halophiles C. psychrophiles
osmophiles D. thermophiles
7. Most of the bacteria pathogenic to man are
A. halophilic C. psychrophilic
B. aerophilic D. thermophilic

TYPICAL BACTERIAL CELL

BACTERIAL STRUCTURE Adherence to surfaces Polysaccharide Glycocalyx vs. phagocytosis Polysaccharide Capsule Division septa Invagination of c.m. Mesosome Hydrolytic enzymes (phosphatases, B-lactamases, etc) Space between c.m. and o.m. Periplasm Osmotic barrier Oxidative and transport enzymes Lipid bilayer Cyto. membrane Endotoxin O antigen Lipid A Somatic O polysaccharide Outer membrane (porin, LPS) Rigid support Protection vs. osmotic pressure peptidoglycan Cell wall 1 , 2 , 3 Function Chem Comp Structure

BACTERIAL STRUCTURE Motility Protein (flagellin): basal body, hook, filament Flagellum Motility of spirochetes Axial filaments Common: attach to cell surface Sex: conjugation Glycoprotein (pilin) Pilus/fimbriae Storage of food and energy Glycoprotein, lipids, polyphosphates Granule Resistance to drying, heat, chemicals, UVL Keratin-like coat, dipicolinic acid Endospore Genes for antibiotic R, toxins DNA Plasmid Genetic material DNA Nucleoid Function Chem Comp Structure

CELL WALL
Peptidoglycan
Glycan:
N-Ac-glucosamine
N-Ac-muramic acid
Tetrapeptide
Crosslink – peptide bridges

Cell Wall-less Forms
Treated with lysozyme or antibiotic (e.g., penicillin)
Protoplasts – from gram positive cells
Spheroplasts – from gram negative cells
L-forms – genetically cell wall-containing
capable of regenerating the cell wall
may be formed spontaneously
produce chronic infections
relatively resistant to antibiotics
Mycoplasma – inherently cell wall-less

COMPARISON BETWEEN GRAM POSITIVE AND GRAM NEGATIVE BACTERIA
Gram positive:
very thick peptidoglycan layers
contains techoic acids
Gram negative:
thinner cell wall
covered by an outer membrane
Has periplasmic space

ENDOSPORES
Bacillus, Clostridium, Coxiella
For survival in adverse environment:
Heat, drying, chemicals, UVL, depelted nutrients
Dehydrated
Dipicolinic acid
Metabolically inactive
Not for reproduction

Each of the following statements concerning bacterial and human cells is correct EXCEPT
A. Bacteria are prokaryotic (ie, they have one molecule of DNA, are haploid, and have no nuclear membrane)
B. Bacteria derive their energy by oxidative phosphorylation within the mitochondria in manner similar to human cells
C. Bacterial and human ribosomes are of different sizes and chemical compositions
D. Bacterial cells possess peptidoglycan, whereas human cells do not

Cell envelopes of both gram positive and gram-negative bacteria are composed of complex macromolecules. Which of the following statements describes both gram-positive and gram-negative cell envelopes?
A. They contain a significant amount of teichoic acid
B. They contain all the common amino acids
C. Their antigenic specificity is determined by the polysaccharide O antigen
D. They are a diffusion barrier to large charged molecules

Each of the ff statements concerning the surface structures of bacteria is correct EXCEPT
A. Pili mediate the interaction of bacteria with mucosal epithelium
B. Polysaccharide capsules retard phagocytosis
C. Both gram-negative rods and cocci have polysaccharides (endotoxin) in their cell wall
D. Bacterial flagella are non-antigenic in humans because they closely resemble human flagella in chemical composition

An aliquot of Escherichia coli is treated with EDTA. The first wash is analyzed and found to contain alkaline phosphatase, DNAse, and penicillinase. The anatomic area of the cell affected is most likely to have been the
Periplasmic space
Mesosomal space
chromosome
plasma membrane

L forms are correctly characterized as:
A. generally susceptible to amphotericin B
B. unable to revert to their bacterial parental types
C. not induced by penicillin or ultraviolet light
D. containing sterols in the membrane

The fine filamentous appendages, arising from basal bodies in the cytoplasmic membrane of many gram negative bacilli are known as
spores
mesosomes
pili
capsules
flagella

The toxic property of endotoxin lies in the
A. protein C D. O antigen
B. polysaccharide core E. lipid A
C. protein A
Septicemic shock from Gram-negative rods is triggered by
endotoxin
exotoxin
Chemotaxis
exaggerated immune response
immune complexes

The substance which is responsible for producing endotoxic shock is
enterotoxin P of Staphylococcus aureus
pyocyanin of Pseudomonas aeruginosa
protein M of Streptococcus pyogenes
lipid A of Neisseria meningitidis
the polysaccharide capsule of Hemophilus influenzae

GROWTH REQUIREMENTS OF BACTERIA
1. Source of Carbon and Nitrogen
autotrophs - use inorganic compounds
-photolithotroph – light as energy source
-chemolithotroph – chemical rxns as energy source
heterotrophs - use organic compounds
-photoorganotroph – light as energy source
-chemoorganotroph - chemical rxns as energy source
2. Vitamins and minerals
3. Amino acids
4. Water
5. pH - 7.2 to 7.6

GROWTH REQUIREMENTS OF BACTERIA
6. Temperature -
psychrophile – 0-20 C
mesophile – 20-40 C
thermophile – 40-80 C
7. Oxygen
obligate aerobes
obligate anaerobes
facultative aerobes/anaerobes
microaerophiles
aerotolerant
O 2
O -2
SOD
H 2 O 2
catalase
H 2 O + O 2

Obligate Anaerobes
Sporeforming – Clostridium
Non-sporeforming
Bacteroides
Fusobacterium
Bifidobacterium
Lactobacillus
Actinomyces
Propionibacterium
Peptococcus
Peptostreptococcus
Veillonella
Nonsporeforming anaerobes:
normal flora: mouth, URT, GIT, CUT
Require low redox potential
Polymicrobic infection

Bacterial Growth Curve # viable cells time a b c d a- Lag phase b- Logarithmic phase c- stationary phase d- decline phase

Optimum pH for growth of most bacteria is
A. 5.5-6.5 C. 8.0-9.3.
B. 7.2-7.6 D. none of the above
Oxygen is toxic to
facultative anaerobes
obligate anaerobes
aerotolerant anaerobes
none of the above

Bacteria that make either a fermentative or respiratory set of enzymes are known as
A. facultative organism C. microaerophiles
B. obligate aerobes D. obligate anaerobes
Bacteria which are able to grow at temperature below 25 o C are called
A. halophiles C. osmophiles
B. psychrophiles D. thermophiles

Which is LEAST acceptable as specimen for the diganosis of anaerobic infections?
Transtracheal aspirate
Suprapubic aspirate
Vaginal swab
Sample from tissue of infected site

What do you call the stage of growth where there is slow loss of cells through death that is just balanced by the formation of few cells through growth and division?
A. Acceleration C. lag
B. Maximum stationary D. exponential
Which is NOT anaerobic?
Fusobacterium D. Clostridium
Bacteroides E. Peptostreptococcus
Branhamella

STERILIZATION AND DISINFECTION

STERILIZATION-DISINFECTION
STERILIZATION- the process of destroying all forms of life including spores

DISINFECTION - does not necessarily destroy all forms of life but aims to destroy the disease-producing organisms

DISINFECTANT - chemical agent used inanimate objects

ANTISEPTIC - chemical agent used to kill organisms on the surface of skin and mucous membrane

A. HEAT: denature proteins, membrane damage or DNA cleavage
1. MOIST HEAT:
a. BOILING: spores are resistant
b. STEAM UNDER PRESSURE ( autoclaving)
-121 C at 15 psi for 15-20 minutes
-kills spores
c. PASTEURIZATION
- 62 C for 30 min. or;
- 72 C for 15 sec.
PHYSICAL AGENTS

2. DRY HEAT:
a. HOT AIR OVEN - 170 - 180 C for 2 hrs
-sporocidal
b. open flame
c. incineration
PHYSICAL AGENTS

B. RADIATION:
-UVL - formation of pyrimidine dimers (DNA)
- 240 - 280 nm.
-X-RAYS, GAMMA RAYS, ETC. - production of free radicals

C. FILTRATION - preferred for certain liquids that are heat-sensitive like serum, enzyme solutions
-membrane filters: 0.22  m
PHYSICAL AGENTS

D. LYOPHILIZATION
- freeze-drying
- rapid freezing and sublimating the ice in a
vacuum
-preservation of cultures (bacteriostatic)

E. REFRIGERATION - bacteriostatic
F. FREEZING - bacteriostatic
PHYSICAL AGENTS

A. DISRUPTION OF CELL MEMBRANES
ALCOHOLS
PHENOL - standard for new chemical agents
CRESOL
HEXACHLOROPHENE
DETERGENTS

B. DENATURE PROTEINS
ALCOHOLS
PHENOL
ACIDS AND ALKALIS
CHEMICAL AGENTS

C. MODIFICATION OF PROTEINS & NUCLEIC ACID
1. HEAVY METALS - oxidizing agents
MERCURY - merthiolate, mercurochrome
SILVER - silver nitrate
2. HALOGENS - SPOROCIDAL
-oxidizing agent: form S-S bonds from -SH groups
CHLORINE - purify water supply
-active component of hypochlorites
IODINE - MOST EFFECTIVE SKIN ANTISEPTIC
-TINCTURE OF IODINE - irritating
-IODOPHORS - less irritating
CHEMICAL AGENTS

3. HYDROGEN PEROXIDE
-oxidize -SH groups
4. ALDEHYDES - alkylate proteins and nucleic acids
-SPOROCIDAL
FORMALDEHYDE
GLUTARALDEHYDE - 10X more effective than
formaldehyde
-cold sterilant
-sterilization of heat-sensitive instruments
5. ETHYLENE OXIDE - alkylating agent
-gas
-SPOROCIDAL
-sterilization of heat-sensitive instruments
CHEMICAL AGENTS

Antimicrobial Agents Drugs Mechanism of Action Penicillins, cephalosporins, imipenem, aztreonam, bacitracin, vancomycin, cycloserine Inhibition of cell wall synthesis Chloramphenicol, erythromycin, clindamycin Aminoglycosides, tetracyclines Inhibition of Protein synthesis Bind to 50S ribosomal subunit Binds to 30S ribosomal subunit -Sulfonamides, trimethoprim -quinolones, novobiocin, Metronidazole Rifampin Inhibition of nucleic acid synthesis Inhibition of nucleotide synthesis Inhibition of DNA synthesis Inhibition of mRNA synthesis

Antimicrobial Agents Drugs Mechanism of Action Alteration of Cell Membrane Polymyxin Antibacterial Isoniazid Others Inhibits mycolic acid synthesis Amphotericin B, nystatin, ketoconazole Antifungal

Figure 5-9 Mechanisms of bacterial gene transfer. (From Rosenthal KS, Tan J: Rapid reviews microbiology and immunology, St. Louis, 2002, Mosby.) Downloaded from: StudentConsult (on 24 September 2006 05:26 AM) © 2005 Elsevier Transformation -the transfer of naked or free DNA -requires competence of recipient cell

Figure 5-9 Mechanisms of bacterial gene transfer. (From Rosenthal KS, Tan J: Rapid reviews microbiology and immunology, St. Louis, 2002, Mosby.) Downloaded from: StudentConsult (on 24 September 2006 05:26 AM) © 2005 Elsevier Transduction - the transfer mediated by a bacteriophage

Figure 5-9 Mechanisms of bacterial gene transfer. (From Rosenthal KS, Tan J: Rapid reviews microbiology and immunology, St. Louis, 2002, Mosby.) Downloaded from: StudentConsult (on 24 September 2006 05:26 AM) © 2005 Elsevier Conjugation -the transfer of DNA thru a cell-to-cell contact -usually involves the sex pilus

Strong mineral acids and alkalis
A. have an antiseptic effect
B. are both contained in Lysol
C. have a disinfectant effect
D. have no relationship to their dissociation in solution
The most effective method of sterilization by heat is
A. steam under pressure C. hot air oven
B. boiling D. live steam

Many of this type of bacteria do not possess superoxide dismutase and catalase
Obligate aerobes
Obligate anaerobes
Facultative anaerobes
microaerophiles

It is the period when the bacterium is assessing the nutrients present in the medium; the bacterium does not divide but there is a intense metabolic activity. The phase of growth is
Lag
Logarithmic
Stationary
Decline

These are groups of genes that are clustered together in the DNA of some bacterial species and which may enable them to invade a host
Pathogenicity island
Episomes
Transposons
Replicons

Which is true about the bacterial chromosome?
Contains histones that stabilize the DNA
Composed of a single pair of homologous chromosomes
Replicates in a very different manner from that of the eukaryotic chromosomes
Contain single copy of each gene

A non-encapsulated strain of Hemophilus influenzae acquires the gene for capsule production from a DNA extract of an encapsulated strain. The event that has occurred is
Transformation
Conjugation
Transduction
transversion

A hospitalized patient with dysuria and suprapubic pain is teated with ciprofloxacin.This antibiotic acts by inhibiting
DNA-dependent RNA polymerase
Protein synthesis by binding with 30S ribosomal subunit
Protein synthesis by binding with 50S ribosomal subunit
Topoisomerase II

Which is the predominant indigenous flora of the colon?
anaerobic, gram negative, non-sporeforming bacteria
anaerobic, gram positive, non-sporeforming bacteria
aerobic, gram negative, non-sporeforming bacteria
aerobic, gram positive, sporeforming bacteria

Gaseous sterilization employs which of the following substances?
A. rocal D. hexachlorophene
B. ethylene oxide E. iodophor
C. glutaraldehyde
Contaminated wound dressings are sterilized best by
A. boiling in water for 1 hour
B. immersion in a quaternary ammonium compound
C. autoclaving for 20 minutes
D. exposure to a germicidal ultraviolet light
E. soaking' in 70 percent ethanol for 2 hours

If an agent is introduced into a growing bacterial colony, cell multiplication ceases; removal of the agent however, allows bacterial cell division to resume. This agent may be described as
A. a disinfectant C. a bacteriostat
B. a bactericide D. an antiseptic
Procedure where organisms are frozen rapidly and dehydrated in a high vacuum container is called
A. Tyndallization C. cephalization
B. Saponification D. lyophilization

Limited primarily to the testing of new bactericidal agents:
A. Zephiran C. benzalkoniun chloride
B. phenol D. Tween 80
The phenol coefficient is
A. a method used to test the bacteriological power of phenol
B. the lowest dilution of unknown disinfectant that kills all types of organisms
C. the highest dilution of unknown disinfectant that kills all types of organisms
D. the standardization of disinfectant by comparison with the lethal action of phenol

Resistance of bacteria to antibiotic is due to
A. chromosomal changes C. plasmids
B. episomes D. all of the above
The indication for the use of two or more antimicrobials simultaneously are as follows, EXCEPT:
A. to mask serious infections
B. to delay the emergence of resistant mutants
C. for mixed infection
D. to achieve bacterial synergism

Each of the following statements concerning the mechanism of action of antimicrobial drugs is correct EXCEPT
A. Vancomycin acts by inhibiting peptidoglycan synthesis
B. Quinolones, such as ciprofloxacin, act by inhibiting the DNA gyrase of bacteria
C. Erythromycin is a bacterial drug that disrupts cell membranes by a detergent-like action
D. Aminoglycosides such as streptomycin are bactericidal drugs that inhibit protein synthesis

A gynecologist wants the hospital to sterilize her fragile stainless steel instruments in preparation for a surgery. Which of the following is the most practical for this purpose?
Wipe well with hypochlorite solution
Spray with ethylene oxide gas
Expose to UVL overnight
Soak in glutaraldehyde solution, then rinse with sterile water

NORMAL FLORA
Most common organism
SKIN - S. epidermidis
NOSE - S. aureus
MOUTH -
- oropharynx – Viridans streptococci
- gingival crevices - Anaerobes
COLON
-adults: OBLIGATE ANAEROBES ( Bacteroides )
-breastfed baby: Bifidobacterium
-formula-fed baby: Lactobacillus acidophilus
VAGINA - Lactobacillus
STOMACH – none
Blood, internal organs – generally sterile

How bacteria produce disease
1. Colonization
Adherence
Pili/ fimbriae
Techoic acid
Adhesins
IgA proteases
Avoiding immediate destruction
Capsule, etc: anti-phagocytic
Streptococcus pyogenes – M protein
Neisseria gonorrheae - pili
Staphylococcus aureus – protein A
IgA protease – Neisseria, Hemophilus, S. pneumoniae

How bacteria produce disease
2. Ablity to survive intracellularly
M. tuberculosis – inhibiy phagosome-lysosome fusion
Listeria – quickly escapes phagosome before fusion
Brucella
Francisella
Legionella
3. Inflammation or Immune-mediated damage
Rheumatic fever - cross-reaction of bacteria-induced Ab with tissue antigens
Delayed type of hypersensitivity
Intracellular bacteria:
Mycobacterium tuberculosis, leprae
4. TOXIN Production

TOXINS
EXOTOXIN ENDOTOXIN

1. Excreted by living Gram 1. Integral part of the cell
positive or negative bacteria wall of Gram negative bacteria
2. Polypeptides complex 2. Lipid A complex (LPS)
3. Heat-labile 3. Heat-stable
4. Highly antigenic 4. Do not stimulate formation of antitoxin
5. Converted to toxoid 5. Not converted to toxoid
6. Highly toxic 6. weakly toxic
7. Nonpyrogenic 7. pyrogenic

The criteria that provide proof that a specific bacterium caused a particular disease is
A. Koch's postulate C. Danyz phenomenon
B. Koch's phenomenon D. none of the above
Each of the following statements concerning endotoxins is correct EXCEPT
A. They are less potent (ie, less active on a weight basis) than exotoxins
B. they are more stable on heating than exotoxins
C. they bind to specific cell receptors, whereas exotoxins do not
D. they are part of the bacterial cell wall, whereas exotoxins are not

The mode of action of oxidizing agents is exemplified by:
A. distribution of the cell membrane or wall
B. damage to DNA
C. protein denaturation
D. removal of free sulfhydryl groups
Ultraviolet light
A. acts as alkylating agent
B. disrupts bacterial cell membrane
C. removes free sulfhydryl groups
D. causes formation of pyrimidine dimers

In the culture for voided urine, the colony count considered significant and indicative of infection is
A. less than 10,000 colonies/ml
B. between 10,000 - 100,000 colonies/ml
C. greater than 100,000 colonies/ml
D. none of the above

MIC in antibiotic susceptibility tests means
A. least concentration that kills the test organism
B. peak concentration that kills the test organism
C. least concentration that inhibits the test organism
D. peak concentration that inhibits the test organism
E. least concentration that inhibits all organisms

Concerning penicillin G
A. it has wide antimicrobial spectrum
B. it rarely elicits allergic responses
C. it is resistant to bacterial beta-lactamase
D. it is destroyed by acid in the stomach

All of the following statements are true concerning transformation EXCEPT
A. A great deal of homology is required between donor and recipient DNA
B. Recipient cells must be, competent
C. Recipient cells become F+
D. DNase can prevent transformation from occurring
E. Soluble, double stranded DNA is required

All of the following statements are, true concerning transduction EXCEPT:
A. Only competent cells can be transduced
B. For specialized transduction to occur a prophage is necessary
C. New genetic material can be transferred to a bacterium via transduction
D. Generalized transduction may occur with lytic phages
E. Lysogenic phages are responsible for the virulence of some bacteria

All of the following statements concerning an episome (F factor) are true EXCEPT
A. Self replicating extra chromosomal DNA
B. Codes for sex pili
C. Can be incorporated into recipient cell genome
D. Codes for common pili
E. Required for conjugation

Which of these is a known virulence factor?
A. Streptococcus pneumoniae capsule
B. Escherichia coli flagella
C. Sex pili of Salmonella typhi
D. Metachromatic granules of Corynebacterium diphtheriae
E. Pyocyanin of Pseudomonas aeruginosa

Which is found in both Gram-positive and Gram-negative bacteria?
A. Endospores
B. Endotoxin
C. Mesosomes
D. Peptidoglycan
E. Teichoic acids

Which if the following is true regarding the bacterial cell?
A. The motility of bacteria is due to flagella, axial filaments or cilia
B. The ability to colonize cell surfaces is dependent on toxin production
C. The ability to survive in soil for long periods of time is dependent on the production of endospores
D. It has the same ribosomes as that of eukaryotic cells

Which of the following agents possess either DNA or RNA?
Viruses
Prions
Bacteria
Fungi

Most pathogenic bacteria grow best at the temperature range of
15-20 o C
30-37 o C
50-60 o C
80-100 o C

A newborn was diagnosed with neonatal meningitis. The causative agent was isolated in the vagina of the mother. Which one of the following microorganisms can be a part of the normal vaginal flora of the mother ad can cause neonatal meningitis?
Mycoplasma pneumoniae
Staphylococcus aureus
Escherichia coli
Streptococcus agalactiae

Almost all parts of the human body are colonized by a diverse group of bacteria that are called normal or indigenous flora. Which of the ff is bacteriologically sterile
Fetus intrauterine environment
Female urethra
GI tract
D. vagina
All of the following are considered normal microbial flora of the colon EXCEPT
A. Bacteroides sp. C. Clostridium sp.
B. Fusobacterium sp. D. Vibrio sp

GRAM (+) COCCI CATALASE TEST STAPHYLOCOCCUS STREPTOCOCCUS COAGULASE MANNITOL SALT AGAR S. AUREUS Novobiocin S S. EPIDERMIDIS S. SAPROPHYTICUS NOVOBIOCIN S. EPIDERMIDIS Sensitive S. SAPROPHYTICUS Resistant (+) (-)

GRAM (+) COCCI CATALASE TEST STAPHYLOCOCCUS STREPTOCOCCUS (+) (-) β -streptococcus S. pyogenes S. agalactiae Bacitracin S CAMP test + Hippurate HOH α -streptococcus S. pneumoniae Viridans Strep Optochin Bile solubility Quellung Animal patho S + + + R - - - γ -streptococcus Enterococcus S. bovis 6.5% NaCl penicillin Grow R No Grow S Gp A Gp B Gp D

S. aureus – resistance to penicillin
beta lactamase – plasmid
altered PBP – chromosomal (e.g., MRSA)
Normal flora Catalase + Coagulase (-) Novobiocin (R) UTI in newly sexually active females S. saprophyticus Predominant skin flora Catalase (+) Coagulase (-) Novobiocin (S) Catheter and prosthetic devices Endocarditis in i.v. drug abusers Adherence: biofilm S. epidermidis B-lactamase Catalase (+) Coagulase (+) MSA (+) Novobiocin (S) Folliculitis, furuncles, carbuncles, impetigo, cellulitis SSS, TSS, osteomyelitis Food poisoning ProteinA TSST-1 Exfoliatin Enterotoxin S. aureus Impt. Feature Distinguishing characteristic Disease Virulence factor Organism

PYR test – pyrrolidonyl arylamidase Normal flora Alpha hemolytic Dental caries Endocarditis Dextran Viridans strep No toxin Vaccine: capsular Alpha hemolytic Optochin (+) Bile solubility (+) Quellung rxn Meningitis (adult) Pneumonia (rusty sputum) Sinusitis Capsule, IgA protease S. pneumoniae (lancet-shaped) Flora colon, URT Alpha, beta or gamma hem., Growth 6.5% NaCl Penicillin R PYR test positive UTI, peritonitis, biliary tract infection, etc E. fecalis (Group D) Vaginal flora, URT Beta hemolytic Catalase (-) CAMP test Hippurate HOH Neonatal sepsis Neonatal meningitis S. agalactiae (Group B) (GBS) No penicillin resistance M12 strain – assoc with AGN Beta hemolytic Catalase (-) Bacitracin (+) PYR test positive ASO Sore throat Scarlet fever Pyoderma Erysipelas Rheumatic fever, AGN M protein Pyrogenic exotoxin S. pyogenes (Group A) (GABS) Impt. Feature Distinguishing characteristic Disease Virulence factor Organism

Of the following bacteria, the most frequent cause of prosthetic heart valve infections occurring within two to three months after surgery is
A. Streptococcus pneumoniae
B. Streptococcus pyogenes
C. Staphylococcus aureus
D. Staphylococcus epidermidis

Three sets of blood cultures were obtained. The aerobic bottle of one set had growth of Staphylococcus epidermidis on the 7-day subculture. This indicates that
A. there was low grade bacteremia
B. the organism is most likely a contaminant
C. the subculture plates were defective
D. the subculture should have been done at 5 days

A urine Gram stain shows gram-positive cocci in clusters. To SPECIATE this organism from culture, the technician should perform a coagulase test and a(n)
A. catalase test
B. novobiocin inhibition test
C. oxidase test
D. B-lactamase test

The organism most commonly associated with neonatal purulent meningitis is
A. Neisseria meningitidis
B. streptococcus pneumoniae
C. group B streptococci
D. Hemophilus influenzae
Isolated from a patient with septicemia is an organism that is Gram-positive, catalase-positive and coagulase-negative. This patient is most likely suffering from
A. endocarditis due to Staphylococcus epidermidis
B. osteomyelitis due to Staphylococcus aureus
C. peritonsillar abscess due to Streptococcus pyogenes
D. meningitis due to Streptococcus agalactiae

All of the following are characteristic of Staphylococcus aureus EXCEPT
Catalase negative
Coagulase positive
demonstrates beta-hemolysis
produces beta-lactamase

The CAMP test is done in pregnant women to identify vaginal carriers of
Listeria monocytogenes
Pasteurella multocida
Legionella pneumophila
A patient with abrupt onset of violent shaking chills a fever of 40.2, pleuritic chest pain/ sputum was productive and rusty colored
Adenovirus
Streptococcus pneumoniae
Pneumocystis carinii
Listeria monocytogenes

The causative organism of erysipelas
Staphylococcus albus
Erysipelothrix insidiosa
Streptococcus beta-hemolyticus
The virulence factor of group A streptococcus is:
A. M protein C. C protein
B. Teichoic acid D. T protein

Bacitracin disc test identifies
A. proteus D. group A streptococcus
B. pneumococcus E. staphylococcus aureus
C. Neisseria
Which of these cultural characteristics is not typical of S. pneumoniae?
A. autolysis in bile
B. grows in the presence of Optochin
C. with types-specific antiserum, capsules swell
D. is alpha-hemolytic

Many organisms have been shown to be resistant to a variety of antibiotics. Bacteria which may be resistant to the action of penicillin due to the production of beta-lactamase include:
A. Corynebacterium diphtheriae
B. Nocardia asteroides
D. Mycobacterium tuberculosis
E. Mycoplasma pneumoniae

Food poisoning that produces gastrointestinal symptoms approximately 1 to 2 hours after eating is most likely to be due to
Salmonella enteritidis
Clostridium perfringens
Campylobacter jejuni

Staphylococcus aureus does NOT cause
cellulitis C. diarrhea
scarlet fever D. impetigo
Mainly associated with acute urethritis and cystitis in women
S. agalactiae
Staph aureus
Staph epidermidis
D. Staph saprophyticus

Staphylococcal scalded-skin syndrome is related to the organism’s ability to produce
A. alpha-toxin D. coagulase
B. extoliatin E. leukocidin
C. Hyaluronidase
Common pathogen in surgical implants:
A. Klebsiella D. S. pyogenes
B. E. coli E. Pseudomonas
C. Staph epidermidis

Viridian streptococci include all of the following, EXCEPT:
S. salivarius C. S. sanguis
S. mitis D. S. faecalis
Glomerulonephritis is an immunological complication of
Staphylcoccal impetigo
Pyelonephritis
Streptococcal pyoderma
Nephron nephrosis
Glomerular ischemia

A rising titer of anti-streptolysin 0 indicates a diagnosis of
erysipelas
acute rheuasatic fever
glomerulonephritis
a recent Streptococcal infection
scarlet fever

Bacitracin disc test identifies
proteus D. group A streptococcus
pneumococcus E. Staphylococcus aureus
Neisseria
The virulence of Streptococcus pneumoniae is a function of its
toxin production
capsule
somatic C-carbohydrate
somatic M-protein

Which is NOT a correct statement regarding- streptococci?
A. Beta (clear)-hemolysis is caused by certain streptococci because they produce enzymes hemolysin that lyse red calls.
B. Streptococci are classified primarily by the antigenic differences in their flagella.
C. Streptococci are gram-positive cocci that typically form chains.
Group A and group B streptococci are in different groups because they have different polysaccharides in their cell wall

Substance responsible for adherence of Streptococcus mutans to smooth surface
lipoteichoic acid D. dextran
lipid A E. peptidoglycan
glucan

Which will differentiate viridans streptococcus from pneumococci?
CAMP test
Optochin test
Catalase test
Bacitracin test

A 46-year old female is diagnosed with subacute bacterial endocarditis. It is most commonly caused by organisms known as
oral streptococci
pyogenic streptococci
enterococci
pneumococci

Sputum culture from a patient with pneumonia revealed beta-hemolytic, catalase-positive cocci. The infecting organism is most probably
S. aureus
S. epidermidis
S. pyogenes
S. pneumoniae

Gram positive cocci and polymorphonuclear leukocytes are obseved on Gram stain of sputum from a 60-year old alcoholic with pneumonia. Culture of the sputum reveals alpha hemolytic, catalase-negative bacteria. Which one of the following lab tests is the most appropriate next step in the definitive identification of this organism?
Bacitracin sensitivity test
beta-lactamase production test
Elek test
Bile solubility test

A 23-valent vaccine is used tomprevent disease caused by
N. gonorrheae
Group B streptococci
S. pneumoniae
H. influenzae type b

The blood culture of a patient with a presumptive diagnosis of endocarditis yields non-hemolytic colonies of Gram positive cocci. The isolate is catalase negative, can grow in 6.5% NaCl and is resistant to penicillin. The isolate is most likely
Enterococci
Streptococcus bovis
Streptococcus mutans

A 16-year old boy, previously diagnosed with rheumatic heart disease, now presents with fever, weakness and palor. Examination reveals a heart murmur and splenomegaly. History reveals an uneventful tooth extraction 14 days earlier. Which of the following is most likely cause of her present condition?
Bacteroides
Enterococci
Viridans streptococci
Pneumococci

NEISSERIAE
Gram negative diplococci, coffee bean-shaped
OXIDASE positive
Sensitive to cold, do not refrigerate specimen
Chocolate agar – normally sterile specimen
Thayer Martin – normally non-sterile specimen
V – vancomycin C – colistin N- nystatin
Pen G, ceftriaxone Vaccine: Strains Y, W-135, C and A; Prophylaxis: rifampin, ciprofloxacin Chocolate agar Thayer Martin Oxidae (+) Glucose (+) Maltose (+) Meningococcemia, Meningitis, Waterhouse- Friedrichsen syndrome Capsule Endotoxin; IgA protease N. meningitidis Ceftriaxone B-lactamase Altered PBP Chocolate agar Thayer Martin Oxidae (+) Glucose (+) Maltose (-) Genital infection Ophthalmia neonatorum Disseminated, septic arthralgia, PID Pili - anti-phagocytic; IgA protease N. gonorrheae Impt. Feature Distinguishing characteristic Disease Virulence factor Organism

All of the following statements are true concerning infection with Neisseria meningitidis EXCEPT
A. It is the most common cause of meningitis overall
B. N. meningitidis is commonly found in the nasopharynx of adult carriers
C. The incubation period is usually less than one week
D. Penicillin G is the drug of choice of meningococcal infection
Which of the following does not contribute to N. gonorrheae of virulence?
A. lipopolysaccharide (endotoxin)
B. Axial filaments (fibrils)
C. IgA protease
D. Pili

Which is the incorrect statement concerning gonorrhea?
A. Infection in men is more frequently symptomatic than in women.
B. The definitive diagnosis can be made by detecting at least a 4-fold rise in antibody titer to Neisseria gonorrhea.
C. The main host defenses against gonorrhea are antibodies, complement and neutrophils
D. A presumptive diagnosis can be made by finding gram-negative kidney-bean shaped diplococci within neutrophils in a urethral discharge.

Organisms that may be mistaken for Neisseria gonorrheae in Gram-stained smears of uterine cervix exudates include:
A. Lactobacillus species
B. Streptococcus agalactiae
C. Pseudomonas aeruginosa
D. Moraxella osloensis

The most common site of asymptomatic gonococcal infection in women is the
A. Vagina
B. Myometrium
C. Urethra
D. endocervix

CSF from a febrile 25-year old man with possible meningitis is rushed to the laboratory for a stat Gram stain and culture. While performing the Gram stain, the technologist accidentally spills most of the specimen. The smear shows many neutrophils and no microorganisms. Since there is only enough CSF to inoculate one plate, the technologist should use
A. blood agar plate
B. chopped meat medium
C. chocolate agar
D. Thayer Martin medium

A newborn manifests eye infection; culture reveals the cause to be Neisseria gonorrheae. How did the baby acquire this infections?
A. Ascending infection from the mother’s lower genital tract to amniotic fluid at term
B. Direct eye inoculation of bacteria from contaminated nursery apparatus
C. During spontaneous vaginal delivery, through an infected birth canal
D. Transplacentally, from an infected mother’s blood to fetus

A case of meningococcal meningitis has been confirmed at a high school in Baguio. A. A. Apart from isolating the patient, what preventive measure should health authorities do?
B. Provide rifampin prophylaxis to all close contacts
C. Quarantine all close contacts in a special ward in the hospital
D. Administer intramuscular penicillin to family an friends
All of the above

All of the following statements are true concerning infection with Neisseria meningitidis EXCEPT
A. It is the most common cause of meningitis overall
B. N. meningitidis is commonly found in the nasopharynx of adult carriers
C. The incubation period is usually less than one week
D. Penicillin G is the drug of choice of meningococcal infection

The most common site of asymptomatic gonococcal infection in women is
A. Vagina C. urethra
B. myocardium D. endocervix
The principal habitat of N. meningitidis in carriers is
A. meninges C. nasal mucosa
B. nasopharynx D. lung

A 19-year old college sophomore does 24 hours after the development of fever, petechiae, purpura and disseminated intravascular coagulation. Culture of CSF and blood from the patient on admission to the hospital most likely yielded
A. Gram negative, lactose fermenting rods
B. Gram negative, oxidase positive diplococci
C. Gram positive, catalase negative cocci
D. Gram positive, catalase positive cocci

CORYNEBACTERIUM
Gram positive bacilli, chinese character arrangement
Exotoxin
lysogenic strains (phage-coded)
Subunit A – inhibits protein synthesis by ADP-ribosylation of EF-2
Subunit B – binding to receptor
TARGET: heart and nerve
Toxemia No bacteremia Antitoxin Toxoid vaccine Schick test Babes Ernst granules (LAMB) Loffler’s med ELEK TEST Diphtheria Bullneck Pseudomembrane exotoxin C. diphtheriae Impt. Feature Distinguishing characteristic Disease Impt. Virulence factor Organism

ELEK TEST – for toxigenicity Filter paper with antitoxin precipitin line Unknown (patient’s isolate) Positive control Negative control

Which statement is NOT correct regarding Neisseria gonorrheae?
A. It grows poorly on bacteriologic media, so diagnosis is primarily made serologically.
B. It produces an IgA protease that degrades secretory IgA thereby enhancing the ability of the organism to colonize the urethral mucosa.
C. Resistance to penicillin is mediated both by plasmid-encoded penicillinase and by changes in chromosome-encoded proteins that control the permeability of the drug.
D. The antigenicity of its pilus proteins varies significantly, thereby allowing the organisms to evade the immune response.

Which is NOT the correct statement regarding C. diphtheriae and the disease diphtheria
A. The antigen in the vaccine is diphtheria toxoid
B. Diphtheria toxin blocks protein synthesis in human cells by inhibiting elongation factor 2
C. The natural habitat of the organism is the soil, where it forms spores
D. inhalation of spores is the main mode of transmission
E. A gram stain of the exudate from the lesion reveals gram positive rods
The test used to determine susceptibility to infection with diphtheria is
A. Dick test C. CAMP test
B. Schick test D. Mantoux test

Concerning diphtheria toxin/ all of the following statements are true EXCEPT
A. Its production is mediated by lysogenic strains of bacteria
B. Polypeptide A is responsible for inactivating elongation factor-2 of protein synthesis
C. Polypeptide B is responsible for the binding and uptake of the diphtheria toxin into the cells.
D. Localized necrosis following an injection of diphtheria toxin indicates immunity
E. It often causes reversible demyelination of cranial nerves resulting in paralysis of throat muscles

All of the following are true concerning Corynebacterium diphtheriae EXCEPT
A. Stained organisms have a characteristic ‘chinese-character’ appearance
B. The organism may be isolated on Loeffler’s media
C. It produces a phage-mediated toxin
D. It is part of the normal flora of the oropharynx

A 6 year old child of Christian Scientists parents has a sore throat, low grade temperature and malaise. The pharyngeal area is covered with a thick grayish material, not easily dislodged. Throat cultures on tellurite containing medium yield dark grayish black colonies of gram-positive rods which stain metachromatically. The presence of a toxin is demonstrated by the Elek test.
A. Bacillus anthracis
B. Hemophilus influenzae
C. Corynebacterium diphtheriae
D. Mycobacterium tuberculosis

The presence of immunity to C. diphtheriae is indicate by
A. Positive Elek test
B. Negative Elek test
C. Positive Schick test
D. Negative Schick test

BACILLUS
Gram positive bacilli in chain, ‘bamboo pole-like’
aerobic, sporeforming
Bacillus anthracis
capsule – polypeptide (poly-D-glutamate)
toxin - Protective Ag, lethal factor, edema factor
Fried rice Meat, sauces Emetic type Diarrhea type enterotoxin B. cereus Zoonotic Medusa head cols. Nonhemolytic nonmotile Malignant pustule Woolsorter’s disease GI anthrax Exotoxin capsule B. anthracis Impt. Feature Distinguishing characteristic Disease Impt. Virulence factor Organism

All of the following are true of Bacillus anthracis EXCEPT
A. Primary disease of herbivorous animals
B. The organism grew well on most common laboratory media like blood agar plate
C. Humans became infected by cutaneous route, inhalation, ingestions and blood transfusion
D. The lethal effect of B. anthracis are due to an exotoxin system
Vomiting and diarrhea occurs in a patient approximately 8 hours after dining at a Chinese restaurant. The causative agent is most likely
A. Bacillus cereus C. S. aureus
B. E. coli D. V. parahemolyticus

CLOSTRIDIUM
Gram positive bacilli
Anaerobic, spore-forming
tetanus toxin- blocks release of inhibitory transmitter
botulinum toxin – blocks release of acetylcholine (lysogeny)
Metronidazole, vancomycin Toxin in stool R to clindamycin, ceph, amox, amp Pseudomembranous colitis Antibiotic- associated diarrhea Exotoxin A and B C. difficile Toxemia Toxin types A,B,E Clinical dx Botulism Flaccid paralysis exotoxin C. botulinum Toxemia Antitoxin (TIG) Clinical dx Tetanus, lock jaw, Risus sardonicus, opisthotonus Tetanospamin (exotoxin) C. tetani Gaspak jar Chopped meat med Non-motile Anaerobic Nagler rxn Stormy ferm milk Myonecrosis Gastroenteritis Enteritis necroticans Alpha toxin (lecithinase, phospholipase C); enterotoxin C. perfingens Impt. Feature Distinguishing characteristic Disease Impt. Virulence factor Organism

MYCOBACTERIUM
Acid-fast bacilli
Obligate aerobes
High lipid content on the cell wall
Resistant to:
Desiccation
Many chemicals
Sensitive to UV
Slow growing 2-3 wks: positive culture
6-8 wks: negative culture
No exotoxins nor endotoxins

Mycobacterium tuberculosis complex
M. tuberculosis
M. bovis
M. africanum

MOTT – Mycobacterium other than tuberculosis Not transmitted person-to-person Acid-fast Opportunistic in immunocompromised Nonchromogen MAI Not transmitted person-to-person Acid-fast M. kansasii- pulmonary M. marinum-skin infection Photochromogens M. kansasii M. marinum Not transmitted person-to-person Acid-fast Cervical lymphadenitis in children Scotochromogens M. scrofulaceum Not transmitted person-to-person Acid-fasst Fast growers (<days) M. fortuitum Cannot grow in artificial media Acid-fast Tuberculoid leprosy Lepromatous leprosy M. leprae Lowenstein Jensen Middlebrook Serpentine growth No serodiagnosis Acid-fast Obligate aerobe Slow growing Nonpigmented Niacin(+) Catalase (68C) (–) Nitrate red’n + TB Cord factor sulfatides M. tuberculosis Impt. Feature Distinguishing characteristic Disease Impt. Virulence factor Organism

Forms of Leprosy Numerous lesions becoming nodular; loss of eyebrows, destruction of nasal septum Paresthesia Leonine facies Fewer lesions: macular, nerve enlargement, paresthesia No. of lesions and other symptoms Large no. of intra. organisms Nerve damage from overgrowth of bacteria in cells Loss of sensation burns and trauma Immune response (CMI killing infected cells) Granuloma formation nerve enlargement/ damage Loss of sensation burns and trauma Damage from High (foam cells totally filled) Low (paucibacillary) No. of org in tissue (-) (+) Lepromin skin test Weak CMI Strong CMI CMI LEPROMATOUS B O R D E R L I N E TUBERCULOID

Actinomyces israelli
Gram positive bacilli, branching filaments
Obligate anaerobe
Normal flora: gingival crevices, intestine, vagina
Transmission: endogenous
Disease: Actinomycosis
Cervicofacial (lumpy jaw), thoracic, abdominal, pelvic, CNS
‘ sulfur granules’ in draining sinus tracts

MYCOBACTERIA AND CLOSE RELATIVES Rods Yes Yes, obligate Mycobacterium Rods, filaments Partial Yes Nocardia Rods, filaments No No, anaerobic Actinomyces Rods No Yes Corynebacterium Morphology Acid-fast? Aerobic growth? Genus

LISTERIA MONOCYTOGENES
Gram positive bacilli
facultative intracellular parasite
tumbling motility in broth; actin jet motility in cells
sources: animals, unpasteurized milk products, soft cheeses, deli meats, cabbages (coleslaw)
Transmission: foodborne, transplacental, during birth

LISTERIA MONOCYTOGENES
Diseases:
Listeriosis – pregnant women (septicemia)
Neonatal disease – granulomatosis infantiseptica
IC patients: septicemia and meningitis
Listeria meningitis is the most common cause of meningitis in renal transplant patients and adults with cancer

The acid-fastness of M. tuberculosis is due to
thickness of the cell wall
the presence of cord factor
mycolic acid
absence of outer membrane

The pathogenesis of Mycobacterium tuberculosis follows certain norms. Which of the following statements is NOT true
A. Dissemination may be by blood stream or erosion of tubercle and spread to contiguous areas
B. The primary lesion usually appears in the lungs
C. Reactivation is seen primarily in debilitated or immunocompromised patients
D. M. tuberculosis produce an exotoxin and contain an endotoxin in its cell wall

One of the following is NOT characteristic of TB and its causative agent?
acid fast stain
absence of pigment
C. niacin positive
D. susceptible to rifampin
E. rapid growth in media
The length of culture incubation for isolation of M. tuberculosis before a final negative report is made:
A. 1 week C. 8 weeks
B. 4 weeks D. 12 weeks

Which of the following statements concerning the transmission of Mycobacteria is true
A. M. kansasii is transmitted from one AIDS patient to another through respiratory droplets
B. M. avium is transmitted human to human
C. M. marinum is contracted through skin contact with contaminated water
D. M. tuberculosis is not transmitted from one AIDS patient to another

A 70-year old woman in a nursing home is treated with a broad spectrum antibiotic for bed sore. Two days later he develops bloody diarrhea. A stool specimen from the patient is positive in an ELISA test for necrotizing cytotoxin, and his treatment is switched to vancomycin. The agent most likely to be responsible for this clinical syndrome is
A. Bacteroides fragilis
B. Campylobacter jejuni
C. Clostridium difficile
D. Escherichia coli O157:H7

The following are some general characteristics of Mycobacterium leprae EXCEPT
A. Human are the natural host of M. leprae
B. A cell wall has high lipid content hence its acid fast property
C. M. leprae can be grown in lab using either artificial media or cell culture
D. Is an acidfast rod

Which of the following statements is true about the two major forms of leprosy (tuberculoid and lepromatous)?
(A) Tuberculoid leprosy is the hardest to treat due to poor cell-mediated immunity.
(B) In either extreme form of leprosy, the lepromin test will be positive.
(C) Diagnostic workup on the patient should include a physical examination, skin test, and cultures.
(D) Biopsy of lesions from a lepromatous leprosy patient will generally be loaded with M. leprae.
(E) Lepromatous leprosy patients usually have few lesions.

The length of culture incubation for isolation of M. tuberculosis before a final negative report is made:
A. 1 week C. 8 weeks
B. 4 weeks D. 12 weeks

A 40-year old tropical fish store owner develops a non-healing ulcer on his left arm. He is afebrile and gives no history of night sweats, weight loss, or other constitutional symptoms. Biopsy of the lesion shows granulomatous inflammation and rare acid-fast organism. A tuberculin test is negative. This man most likely has an infection caused by
A.Mycobacteria marinum
B. Mycobacteria ulcerans
C. Mycobacteria tuberculosis
D. Mycobacteria kansasii

Members of the genus Mycobacterium stain better with the acid-fast stain than with the Gram stain. Which of the following is the BEST explanation for this finding?
A. they lack a cell wall; therefore, they cannot absorb the crystal violet
B. they have a very thin cell wall that does not retain the crystal violet
C. They have a thick polysaccharide capsule that prevents entry of the iodine solution
D. they have a large amount of lipid in their cell wall that prevents entry of the crystal violet

Diagnosis of tetanus is usually made through
A. culture of organism from lesion
B. demonstration of antibodies against Clostridium tetani
C. clinical manifestation
D. demonstration of toxic metabolites

Activated macrophages are the effector cells in the expression of a protective, cell-mediated immune response against
A. Corynebacterium diphtheriae
B. Haemophilus influezae type b
C. Listeria monocytogenes
D. Streptococcus pneumoniae

Listeria monocytogenes infection of an adult is MOST likely to be acquired by
A. ingestion of contaminated food
B. inhalation of contaminated aerosols
C. inosculation with a contaminated needle
D. person-to-person contact

Bobby was diagnosed with lung cancer and in his bronchial washing acid-fast bacilli were seen mixed with the cancer cells, Bobby had been given the full short course of the TB regimen before and so the doctor suspected a drug resistant strain. The bronchial washing was cultured and it grew orange colored colonies when exposed to light. The most probable etiologic agent is
A. Mycobacterium tuberculosis
B. Mycobacterium smegmatis
C. Mycobacterium kansasii
D. Mycobacterium avium complex

A definitive identification of Mycobacterium tuberculosis can be obtained by doing the following procedure
A. Ziehl Neelsen stain
B.AFB culture
C. Biopsy of tuberculin test
D. Nucleic acid amplification

Rifampin, a broad spectrum antimicrobial agent, is effective treatment for tuberculosis by
A. Selective inhibition of the biosynthesis of the arabinogalactan and lipo-arabinomanan
B. Mediating drug permeability and efflux
C. Inhibiting peptidoglycan synthesis by blocking action of D-alanine synthesis
D. Binding to RNA polymerase thereby interfering with mRNA synthesis

In primary disease, M. tuberculosis survives and grows within these host cells
Macrophages
Basophils
Neutrophils
eosinophils

Mycobacteria are usually differentiated by the following properties EXCEPT
Rate of growth
Colonial morphology
Pigmentation
Acid-fast staining

Which is regarded as a TB marker in the diagnosis of tuberculous effusion?
Gamma interferon
AFB smear
Caseation necrosis
PPD positivity

Mycobacterium tuberculosis is a unique species. Which of the following statements is true about this bacterium?
Humans are the natural reservoir of this particular species
Its ‘cord factor’ is responsible for its acid-fastness
It will grow in the laboratory only under strict anaerobic condition
Its virulence is mainly due to the production of mycolic acid

GRAM NEGATIVE BACILLI

Enterobactericeae
Members of the Family
ESCHERICHIA Coliforms
KLEBSIELLA (Lactose fermenters – pink colonies)
ENTEROBACTER
SALMONELLA
SHIGELLA Intestinal pathogens
YERSINIA
PROTEUS PROVIDENCIA
MORGANELLA SERRATIA
CITROBACTER EDWARDSIELLA
CEDECEA KLUYVERA
Non - Lactose Fermenters (colorless colonies)

ENTEROBACTERIACEAE
Facultative anaerobes
OXIDASE NEGATIVE
All ferment glucose
Most are motile (peritrichous flagella)
Except: Klebsiella, Shigella
Media
Differential: EMB, McConkey
Highly selective: Hektoen enteric agar, SSA, XLD agar
Antigens:
O – somatic O polysaccharide (LPS)
H - flagellar
K- envelope or capsular

Opportunistic Enterobacteriaceae
Normal flora of the colon
Immunocompromised
Community-acquired or nosocomial
Infections outside the intestine
Any tissue
Common types of infections
UTI - meningitis
Septicemia - wound infections
Pneumonia - various GI disorders

Klebsiella pneumoniae
Capsule, non-motile, lactose fermenter
Pneumonia: ‘currant jelly sputum’
Chronic lung disease, alcoholism, diabetes
Proteus spp.
Urease, phenylalanine deaminase
Alkaline urine (staghorn urinary calculi)
‘ Swarming phenomenon’
Cross-rxn with Rickettsiae
Serratia marcescens
3 enzymes: gelatinase, DNAse, lipase
Salmon red pigment
Opportunistic Enterobacteriaceae

ESCHERICHIA COLI
Most abundant aerobic flora of the colon
Index for fecal pollution of water
Major cause of neonatal sepsis & meningitis
Most common cause of gram neg infections
Causes intestinal and extraintestinal infections

Shiga-like toxin – inhibits protein synthesis by binding with 60S ribosomal subunit Persistent diarrhea Childhood diarrhea Fimbriae: ‘stacked brick-like’ biofilm; enterotoxin EAEC O157:H7 Bovine feces hamburger Sorbitol McConkey: NOT ferment SORBITOL Watery diarrhea Hemorrhagic colitis HUS Shiga-like toxin (Stx) (verotoxin) EHEC (VTEC) (STEC) 2 nd to Rotavirus Infantile diarrhea A/E; bundle-forming pili EPEC Watery diarrhea Dysentery (10%) Invasion and destruction of colonic epithelium EIEC Non-invasive Self-limited Toxin immunoassay Travellers’ diarrhea Childhood diarrhea LT – Adenyl cyclase ST- guanylate cyclase ETEC GASTROENTERITIDES/DIARRHEAS septicemia endotoxin E. coli 2 nd to GBS Neonatal sepsis and meningitis K1 capsule endotoxin E. coli Most common cause Lactose fermenter; TSI: A/A + gas; Pink colonies; Greenish metallic sheen UTI P-pili B-hemolysin E. coli Impt. Feature Distinguishing characteristic Disease Impt. Virulence factor Organism

SALMONELLA ENTERICA
Non-lactose fermenter
sensitive to acid
Most Salmonella: acquired from animal sources – meat, chicken, milk
Serotype typhi : human only
3 clinical entities:
Gastroenteritis
Septicemia
enteric fever (typhoid and paratyphoid fever)
Infects animals (chicken, turtles, etc) Non-lactose fermenter; TSI- K/A + H2S Gastroenteritis Septicemia Osteomyelitis in sickle cell disease S. typhimurium, enteritidis, etc. No animal reservoir; Sickle cell disease Carrier: gallbladd Blood culture-best Non-lactose fermenter; TSI- K/A + H2S, no gas WIDAL TEST Typhi Dot Typhoid fever Vi Ag, Endotoxin, Intracellular mult S. typhi Impt. Feature Distinguishing characteristic Disease Impt. Virulence factor Organism

Shiga toxin – subunit A – inhibits protein synthesis by binding to 60S ribosomal subunit subunit B – binding to receptor 3 activities: neurotoxic, cytotoxic, enterotoxic Infects animals Mimics appendicitis Non-lactose fermenter; TSI- K/A Cold enrichment Bloody diarrhea Enterotoxin Y. enterocolitica Not infect animals No bacteremia Lowest ID50: 100 Non-lactose fermenter; TSI- K/A; No H 2 S Bacillary dysentery: Painful passage (tenesmus) of bloody and mucoid stool Shiga toxin Invasiveness – ulcer at ileum and colon Shigella S. dysenteriae S. sonnei S. flexneri S. boydii Impt. Feature Distinguishing characteristic Disease Impt. Virulence factor Organism

Two children were bragging about their intelligence. " When I was eight months old, I could walk,” said one. You call that intelligent?” responded the second child. “When I was that old, I let them carry me.

VIBRIOS
Gram negative curved bacilli
Oxidase +
Single polar flagella
Grow well in alkaline pH (up to 9)
Medium: TCBS (thiosulfate citrate bile salt sucrose agar)
Seafoods halophilic Gastroenteritis Hemolysin V. parahemolyticus No vertebrate carrier Permanent carrier: rare TCBS agar (yellow colonies) Oxidase (+) Alkaline pH Not halophilic Asiatic cholera Severe dehydration ‘ Rice water stool’ Cholera toxin- adenyl cyclase cAMP V. Cholerae O1 – eltor & cholerae O139- toxin, too Impt. Feature Distinguishing characteristic Disease Impt. Virulence factor Organism R S Polymyxin B + - Voges Proskauer test + - Agglutination of sheep rbc Eltor Classic (cholerae)

CAMPYLOBACTER
Gram negative curved bacilli (“gull wing’)
Oxidase +
MICROAEROPHILIC ( CO 2 , O 2 )
grow at 42 C
Media: Skirrow’s, Butzler’s
zoonotic
Urease (+) Breath Test Biopsy Gastritis, peptic and duodenal ulcer, gastric CA (type 1 carcinogen-WHO) Urease, motility, mucinase invasive H. pylori Infects animals Butzler’s med Skirrow’s med ‘ gull wing-shaped Microaerophilic Thermophilic Bloody diarrhea Enterotoxin C. jejuni Impt. Feature Distinguishing characteristic Disease Impt. Virulence factor Organism

X factor only ‘ school of red fish’ Chancroid (soft chancre) Painful genital ulcer Bubo H. ducreyi Chocolate agar Levinthal med X and V factors Satellite phen Pneumonia bronchitis Meningitis Acute epiglottitis Otitis media Capsule (PRP) -type b Endotoxin IgA protease H. influenzae Impt. Feature Distinguishing characteristic Disease Impt. Virulence factor Organism No bacteremia Vaccines: killed org toxoid lymphocytosis Bordet Gengou med; Regan-Lowe med Pertussis, catarrhal paroxysmal (whooping cough) convalescence Capsule Toxin – ADP ribosylation B. pertussis

Zoonotic (domestic livestock) Transmitted by fleas Brucella agar Serologic confirmation Undulant fever Acute septicemia Facultative Intracellular parasite Brucella B. abortus B. suis B. melitensis Air conditioning; cooling towers; excavations No human-to-human transmission Dieterle stain, CYE med Opportunistic Immunocomp Legionaire’s dis. (atypical pneumonia) Pontiac fever Facultative intracellular L. pneumophila flea Bubonic plague Septicemic plague Pneumonic plague V and W Ag coagulase Y. pestis Water aerosols, raw vegetables, flowers Resistant to chem. agents, antibiotics; Oxidase + NONFERMENTING Bluish green pigment-pyocyanin Grape-like odor Obligate aerobe Nosocomial infection Burns, Immunocompromised (eg.,cystic fibrosis), ‘ hot tub folliculitis’ Echtyma gangrenosum Exotoxin - (target: liver); Capsule/slime layer P. aeruginosa Impt. Feature Distinguishing characteristic Disease Impt. Virulence factor Organism

Which of the following is NOT TRUE of E. coli?
A. can cause meningitis in neonates
B. used as index of fecal contamination of water
C. the most frequently isolated gram negative organism from infections
d. the most abundant flora of the colon
Acute gastroenteritis that occurs 24 hours after a patient attended an outdoor barbeque where the menu consisted of chicken, baked beans and beer is most likely due to
A. Salmonella typhi D. Salmonella serotype
B. Salmonella typhimurium E. Shigella flexneri

What is the virulent factor of E.coli responsible for its causing meningitis in infants?
A. enterotoxin C. K Ag
B. exotoxin D. Protein
Your patient, 40-years old, has had severe diarrhea for the past 2 days, accompanied by fever and a shaking chill. From both the blood culture and the stool culture, a gram-negative rod was isolated that does not ferment lactose. Which one of the following organisms is the MOST likely cause?
A. Haemophilus influenza C. Shigella sonnei
B. Salmonella enteritidis D. Escherichia coli

Which of the following is LEAST associated with enterohemorrhagic E. coli?
Fermentation of sorbitol
Strain O157:H7
Undercooked hamburger
Hemolytic uremic syndrome

Which of the following is ture about cholera and its causative agent?
A secretory diarrheadue to increases in cGMP in the intestinal cells
The stool is described as ‘rice water-like’
The causative agent is non-motile, nonfermentative
Grows poorly in medium with alkaline pH

Which of the following is LEAST associated with Helicobacter pylori
It requires at least 2% NaCl for growth (halophilic)
It requires increased carbon dioxide tension and decreased oxygen tension
It is sensitive to the acidity of the gastric juice
Most commonly diagnosed by the demonstration of urease production

In which type of diarrhea is the use of antibiotics not recommended
Salmonellosis
Campylobacter infection
Cholera
Shigellosis

Which cause UTI characterized by alkaline urine and formation of urinary calculi?
Shigella dysenteriae
Escherichia coli
Proteus mirabilis
Enterobacter cloacae

A 2-year old boy presents with fever, headache, stiff neck and signs of meningeal irritation. CSF sent to the laboratory shows Gram negative rods and plenty of PMNs. Cultures on blood agar and McConkey agar are negative., but the chocolate agar incubated in CO2 shows few colonies. Which is the most likely causative organism?
Hemophilus influenzae
Klebsiella pneumoniae
Neisseria meningitidis
Streptococcus pneumoniae

A 34 year old market vendor presents with explosive watery diarrhea and marked dehydration. The most likely cause is Vibrio cholerae. What is the expected culture characteristic of this organism?
Grayish brown matt colonies on chocolate agar
Greenish transparent colonies on McConkey agar
Mucoid raised opaque colonies on blood agar
Yellowish colonies on thiosulfate citrate bile salt sucrose agar

Which one of the following bacterial pathogens requires selective culture conditions for reliable isolation from the stool, including media with antibiotics and incubation at 42 o C in increased CO 2 ?
Enterohemorrhagic E. coli
Salmonella spp.
Shigella spp.

Which one of the following is considered facultative intracellular in human macrophages?
Enteroinvasive E. coli
Enterotoxigenic E. coli
Salmonella spp.
Shigella spp.

A 35-year old male park ranger in rural Arizona arrives to an emergency room with fever and signs and symptoms of septic shock. An enlarged lymph node is discovered under his arm upon P.E. Gram negative coccobacilli that demonstrated bipolar staining were seen in both lymph node aspirate and spinal fluid from the patient. Which of the following is the most likely etiologic agent of this patient’s illness?
Brucella abortus
Borrelia burgdorferi
Chlamydia trachomatis
Yersinia pestis

A 40-year old male hog farmer complains of intermittent fever, night sweats and headaches to his physician. The patient is hospitalized and blood and bone marrow specimens were collected. The physician requests that the laboratory incubate cultures for at least 6 weeks. Nine days after admission, Gram negative coccobacilli that required CO2 for growth were isolated from the blood and bone marrow. The patient is most likely to be suffering from which one of the following diseases?
Brucellosis
Bubonic plague
Legionaire’s disease
Rocky Mountain spotted fever

A 20-year old woman comes to your clinic complaining of an irritating vaginal discharge. Upon examination, you find that the cervix and vaginal walls appear normal. The discharge is thin and milky, pH 5.5, and has a fishy odor when treated with potassium hydroxide. You are unable to detect pseudohyphae, buds ot flagellates upon microscopic examination. A Gram stain reveals numerous Gram negative rods, epithelial cells and clue cells, but relatively few Gram positive rods or WBCs. Cervical and vaginal cultures are negative for STDs. What is your diagnosis?
Bacterial vaginosis
Cervicitis
Trichomoniasis
Vaginal candidiasis

Characteristics of Most Common Types of Vaginitis and Vaginosis 5-6 Above 4.5 Below 4 pH (normal = 3.8-4.2) Tender, red Pink Dry, red Appearance of vaginal mucosa Copious Copious Varies Amount of discharge Frothy Thin. frothy Curdy Consistency of discharge Greenish-yellow Grayish white White Color of discharge Foul Fishy Yeasty or none Odor Protozoa T. vaginalis Bacterium G. vaginalis Fungus C. albicans Agent Trichomoniasis Bacterial Vaginososis Candidiasis

A 50-year old doctor complains of recurrent epigastric pain and abdominal fullness. His attending gastroenterologist suspects Helicobacter pylori infection, for which a test can be performed to detect the bacterial production of which enzyme?
Catalase
Peptidase
Oxidase
urease

A 20-year old woman died after eating hamburger in a fast food restaurant. She had manifested abdominal cramps, vomiting and blood diarrhea. Which of these organisms in the contaminated hamburger was the most likely causative agent?
Bacillus cereus
Escherichia coli
Rotavirus
Salmonella typhi

The mechanism of action of exotoxin A of Pseudomonas aeruginosa is
Activation of acetylcholine esterase
Blocking of elongation factor 2 (EF2)
Increase cAMP
Hydrolysis of lecithin to phosphorylcholine and diacylglycerol

This gram negative rod is described to have ‘gull wing’ shape
Plesiomonas
Aeromonas
Campylobacter
Vibrio

Which specimen should NOT be refrigerated after collection even if processing cannot be done at once?
Stool
Urine
Blood
Sputum

The most frequently isolated type of H. influenzae in cases of bacterial meningitis in children between 6 months and 2 years is
Serotype a
Serotype b
Serotype c
Serotype d

One of the following is the appropriate sample for the isolation of Salmonella typhi during the first week of a suspected case of typhoid fever
Blood
Fecal material
Urine’
CSF

Which of the following organisms is MOST likely to involve invasion of the intestinal mucosa?
Vibrio cholerae
Shigella sonnei
Enteritoxigenic E. coli
Clostridium botulinum

Which of these organisms is a major pathogen for nosocomial infectios because of its ubiquitous presence in the hospital environment?
S. aureus
S. epidermidis
S. marcescens
P. aeruginosa

Among the Gram negative tods producing gastroenteritis, the most infectious is
V. cholerae
E. coli (O157)
S. typhimurium
S. dysenteriae type 1

Which the most infectious stage of pertussis?
Catarrhal
Prodromal
Paroxysmal
convalescence

SPIROCHETES
Gram negative: cannot be seen, very thin
Motile, axial filaments
Ticks (Ixodes) Lyme disease Erythema chronicum migrans B. burdorgferi Human louse ticks Wright’s stain-peripheral blood Relapsing fever B. recurrentis B. hermsii Urine, excreta of rodents Spiral with hook at one or both ends Fletcher’s med Leptospirosis Weil’s disease L. interrogans Not grow in artificial med; Reagin, treponemal Ab Darkfield or IF – 1 o 2 o Sy Serology-2 o & 3 o Sy Syphilis 1 o – hard chancre 2 o – condylomata lata Latent Sy 3 o -gumma Congenital syphilis No toxins T. pallidum Impt. Feature Distinguishing characteristic Disease Impt. Virulence factor Organism

A male crab met a female crab and asked her to marry him. She noticed that he was walking straight instead of sideways. Wow, s he thought , this crab is really special. I can’t let him get away. So they got married immediately. The next day she noticed her new husband walking sideways like all the other crabs, and got upset. “What happened?” she asked. “You used to walk straight before we were married. “ Oh, honey,” he replied. “I can’t drink that much everyday.”

MYCOPLASMA
Smallest free living bacteria
No definite shape, not seen in Gram staining
PPLO agar
require cholesterol for growth
Cell-wall-less Urease + NGU Can cause urinary calculi U. urealyticum Requires sterol for growth Most common pneumonia in young adults Cell-wall-less ‘ fried egg’ colonies, Cold agglutinins Complement fixation Primary atypical pneumonia walking pneumonia tracheobronchitis P1 protein – attachment Not invasive M. pneumoniae (Eaton Agent) Impt. Feature Distinguishing characteristic Disease Virulence factor Organism

CHLAMYDIAE
Obligate intracellular parasites (no ATP)
Cannot grow in artificialmedia
Gram negative, not seen
Elementary body – infective form
Reticulate body – reproductive form
Cell wall lacks muramic acid
Tetracycline Serologic test respiratory droplets humans Atypical pneumonia C. Pneumoniae TWAR agent erythromycin tetracycline Giemsa stain: inclusion bodies in epithelial cells Immnunofluore-scence Cell culture direct contact, sexual contact, perinatal transmission humans A-B - trachoma, D-K - inclusion conj., NGU, PID, pneumonia, L1-L3 - LGV C. trachomatis tetracycline Serologic test inhalation of dried bird feces birds Psittacosis (pneumonia) C. psittaci Treatment Diagnosis Mode of Transmission in Humans Natural Host Disease Medically Important Species

CHLAMYDIA: Developmental Cycle

RICKETTSIAE
Genera:
Rickettsia, Coxiella, Orientia, Ehrlichia
Obligate intracellular parasites
Gram negative but stain poorly
Cross-react with Proteus (OX2, OX19, OXK)
WEIL-FELIX TEST
Transmitted by arthropods
Exception: Coxiella burnetii (Q Fever)
Infections: rash, fever
Except: Q fever

Diseases Etiologic agent Arthropod vector
1. Epidemic typhus fever Rickettsia prowazeki human louse
2. Brill-Zinsser Disease R. prowazeki NONE
3. Endemic typhus R. typhi flea
4. Scrub typhus O. tsutsugamushi mite
5. Rocky Mountain Spotted F. R. rickettsii tick
6. Rickettsialpox R. akari mite
7. Q fever C. burnetii NONE: inhalation
8. Senetsu fever E. senetsu ingestion of raw fish
9. Ehrlichiosis E. chaffeensis tick
RICKETTSIAE

Which of the following statements regarding serodiagnosis of Treponema pallidum disease (syphilis) is correct?
(A) The Venereal Disease Research Laboratory (VDRL) test is highly specific and remains positive for life even if the patient is treated with antibiotics.
(B) Biologic false-positive results are more common with the microhemagglutination assay for T. pallidum (MHA-TP) than they are with the rapid plasma reagin (RPR) test.
(C) Congenital syphilis can be determined at birth by the IgG Fluorescent Treponemal Antibody-Absorption test (FTA-ABS).
(D) If early infection or previous infection needs to be documented, the best test is the FTA-ABS test.

Which one of the following statements regarding Treponema pallidum is most accurate?
A. Despite the therapeutic use of penicillin for many years, no penicillin-resistant strains of T. pallidum have been isolated.
B. Specimens cultured on blood agar plates reveal alpha-hemolytic colonies.
C. Since the lesions of primary syphilis are primarily due to an immune response against the organism, the lesion typically contains few T. pallidum cells.
D. It is a spiral-shaped rod that appears gram-positive in gram stained smear

In Weil's disease or acute leptospirosis, the organs most prominently affected by infection are
A. pancreas and thyroid
B. brain and heart
C. lung and heart
D. liver and kidneys

The resting site for leptospirosis in the natural host is the
lumen of the nephrotic tubules
liver hepatocytes
endothelium
eyes

Diagnosis of leptospirosis is established in the laboratory by the following methods EXCEPT
Demonstration of the organisms by direct darkfield microscopy
Serological test
Culture
Gram stain of infected tissue

Lyme disease is an endemic inflammatory disorder with this distinctive skin disorder
Chronic dermatitis
Erythema marginatum
Erythema chronicum migrans
Erythema gangrenosum

Serology in the diagnosis of syphilis using a non-treponemal test is
Microhemagglutination assay
Venereal Direase Research Laboratory
FTA-Abs test
Reiter Protein Complement fixation test

The appearance of moist pale papules or colylomas in the anogenital area is characteristic of
Primary syphilis
Secondary syphilis
Tertiary syphilis
Latent syphilis

Which is the only disease that can be diagnosed by demonstration of spirochetes in peripheral blood smear?
Relapsing fever
Leptospirosis
Pinta
Lyme disease

The smallest bacteria cultivated on a -cell-free media are
A. Rickettsiae
B. Chlamydiae
C. Mycoplasrna
D. Mycobacteria

The following statements are true about Chlamydia trachomatis EXCEPT
Is has a reservoir in domestic fowls
It the most common cause of NGU
It can be detected by direct immunofluorescence in specimens
Causes infections in newborns

Chlamydia and Rickettsiae are correctly described, as
A. dividing solely by binary fission
B. containing either RNA or DNA but not both
C. spread by the bite of an infected arthropod
D. resistant to the usual broad-spectrum antibiotics
E. obligate parasites of living cells

Which of the following statements regarding Rickettsial infections is correct?
(A) The rash caused by R. rickettsii generally starts on the ankles or wrists and spreads to the trunk of the body.
(B) The rash of Coxiella burnetii starts on the trunk and spreads to the periphery but spares the palms and soles.
(C) The rash of R. prowazekii starts on the extremities and spreads to the trunk.
(D) R. tsutsugamushi infections have no rash.

A 4-yea old Asian child develops an infection with Chlamydia trachomatis. How does infection with this organism cause blindness?
Retinal detachment
Cataract formation
Hemorrhage of the anterior chamber
Scarring of the cornea

Which of the following is associated with atherosclerosis?
K. pneumoniae
C. trachomatis
S. pyogenes
C. pneumoniae

Which of the following is the LEAST effective against M. pneumoniae?
Erythromycin
Tetracycline
Kanamycin
vancomycin

Beta-prophage plays an important role in the toxigenicity of
A. Staphylococcus aureus
B. Mycobacterium kansasii
C. Clostridium tetani
D. Corynebacterium diphtheriae
E. Vibrio cholera

Each of the following microorganisms are responsible for zoonotic infections EXCEPT:
A. Campylobacter jejuni
B. Shigella sonnet
C, Vibrio parahemolyticus
D. Pasteurella multocida
E. Leptospira interrogans

Which of the following is a zoonotic disease?
A. Enterotoxigenic 'Escherichia coli
B. Enterohemorrhagic Escherichia coli
C. Salmonella enteritidis
D. Shigella sonnei
E. Mycobacterium leprae

Regarding Chlamydia trachomatis which statement is NOT true
A. Reticulate bodies are able to synthesize their own DNA, RNA and proteins
B. Serovars which cause trachoma replicate in epithelial cells of mucosal surfaces
C. Serovars which cause lymphogranuloma venereum (LGV) are associated with systemic infection involving lymphoid tissues
D. Ocular infections are most frequently treated with tetracycline(s)
E. Culture is the major diagnostic tool in most labs

All of the following statements are true concerning chlamydia EXCEPT
A. Obligate intracellular parasite
B. Not seen in Gram Stains of discharge
C. TWAR Agent
D. Elementary bodies are infectious
E. Makes own ATP

Chlamydia resemble bacteria in all of the following ways; EXCEPT:
A. they possess both RNA and DNA
B. they can be inhibited by many antibiotics effective against bacteria
C. they are closely related to gram-positive bacteria
D. they multiply by binary fission
Mycoplasma pneumoniae infection can be diagnosed by both serological findings and culture. Which is the most sensitive and specific of the following serologic methods? A. cold agglutinins C. immunodiffusion B. complement fixation D. Quellung test

Gram Negative Enteropathogens:
Enterobacteriaceae (E. coli, Salmonella, Shigella, Yersinia)
Vibrios
Campylobacter
Gram Positive Enteropathogens
S. aureus
B. cereus
C. perfringens
C. defficile

Gastritis Peptic and duodenal ulcer Gastric CA C. jejuni – gastro C. fetus - septicemia V. cholerae- cholera V. Parahemolyticus - Diarrhea (seafds) Disease Skirrow’s med Butzler’s med Skirrow’s med Butzler’s med TCBS Medium (+) (-) (-) Urease (-) (-) (+) Alk. pH thermophilic microaerophilic Oxidase test flagellum Gram stain (-) (+) 42 C (-) (+) (+) (-) (+) (+) (+) Single polar Single polar Single polar Gram (-) curved, S, U-shaped rod Gram (-) ‘gull-wing’ bacillus Gram (-) curved bacillus Helicobacter Campylobacter Vibrio

Spore-formers
Bacillus
Clostridium
Coxiella
No bacteremia diphtheria pertussis shigellosis tetanus botulism cholera

Important Bacterial Exotoxins: Inactivates EF-2 by ADP-ribosylation P. aeruginosa Activates adenylclase by ADP-ribosylation B. pertussis Activates adenyl cyclase V. cholerae Shiga-toxin – binds to 60S ribosomal subunit Shiga-like toxin S. dysenteriae Other Shigella spp ETEC – activates adenyl cyclase by ADP-ribos EHEC – shiga-like toxin E. coli Pyrogenic exotoxin – a superantigen S. pyogenes TSST – a superantigen S. aureus 3 toxins; one is an adenyl cyclase B. anthracis Alpha toxin (lecithinase)- damages membrane Enterotoxin - a superantigen C. perfringens Exotoxin B is cytotoxic to enterocytes C. difficile Blocks release of acetylcholine C. botulinum Block release of inhibitory transmitter Glycine C. tetani Inactivates EF-2 by ADP-ribosylation C. diphtheriae

Intestinal Pathogens from Animals
Salmonella
Yersinia
Campylobacter
V. parahemolyticus

REMEMBER!
Pathogens primarily within the GI tract
(usually no bacteremia)
Shigella
Vibrio cholerae
Vibrio parahaemolyticus
Helicobacter pylori

REMEMBER! (most important encapsulated org) S ome K illers H ave P retty N ice C apsule S treptococcus pneumoniae K lebsiella pneumoniae H aemophilus influenzae P seudomonas aeruginosa N eisseria meningitidis C ryptococcus neofromans

cAMP (Toxins) C – cholera A – anthrax Σ – E. coli LT P - Pertussis

“ Do you think I’ll live another 50 years, Doc?” asked a patient. “ How old are you now?” “ Forty.” “ Do you drink, gamble or chase women?” “ No,” the man answered. “I don’t drink, I never gamble, and I detest women. In fact I don’t have any vices at all.” “ Why then,” the doctor retorted, “do you want to live another 50 years?”

IMMUNOLOGY

2 Types of Host Defenses
INNATE or Non-specific resistance
Defense against any pathogen
First line of defense: skin and mucous membranes
Second line of defense: phagocytes, inflammation, fever and antimicrobial substances
Lysozymes, IFN, complement
No memory

ADAPTIVE IMMUNITY (Acquired Immunity)
Requires prior exposure to the microorganism
Specific – produced only against a particular pathogen
Function of Lymphocytes (T cells and B cells)
Has memory

ANTIGENS
ANTIGEN (IMMUNOGENS) – any substance that stimulates an immune response and reacts only with the product of response (antibody or T cells)
Chemical nature of antigens – proteins, glycoproteins, polysaccharides
Requirements for immunogenicity
Foreign
M.W. = 10,000 or higher
Chemically complex

DEVELOPMENT OF THE IMMUNE SYSTEM BONEMARROW THYMUS BONEMARROW T CELLS B CELLS PRIMARY LYMPHOID ORGANS Lymph nodes, spleen, tonsils, Peyer’s patches SECONDARY LYMPHOID ORGANS

T CELLS B CELLS CELL-MEDIATED IMMUNITY HUMORAL IMMUNITY
CD4+ T cells
CD8+ T cells
Memory T cells
B cells ------- plasma cells ---------- antibodies
Memory cels

CELL-MEDIATED IMMUNITY
protection against intracellular organisms like viruses and TB bacilli
Protection against tumors
Responsible for transplant rejection

Types of T Cells
CD4+ T cell (helper T cells) – peptide+ MHC class 2
TH1 - produce cytokines that activate cells related to CMI:
-macrophages
-CD8+ T cells
-Natural killer cells
- Involved inflammation and delayed type of
hypersensitivity
b. TH2 cells – produce cytokines that
help B cells to produce antibodies

Figure 13-2 MHC restriction and antigen presentation to T cells. Left, Antigenic peptides bound to class I MHC molecules are presented to the T-cell receptor (TCR) on CD8 T killer/suppressor cells. Right, Antigenic peptides bound to class II MHC molecules on the antigen-presenting cell (APC) (B cell, dendritic cell, or macrophage) are presented to CD4 helper cells and delayed-type hypersensitivity T cells. Downloaded from: StudentConsult (on 23 September 2006 05:04 AM) © 2005 Elsevier

2. CD8+ T CELLS
Tc cell (cytotoxic T cell) – peptide + MHC class 1
Kill target cell on direct contact
Important in killing virus-infected cells

HUMORAL IMMUNITY
Antibodies or Immunoglobulins

SUMMARY OF IMMUNOGLOBULIN CLASSES Allergic reactions; possibly lysis of parasitic worms Serum function unknown; presence on B cell functions in initiation of immune response Localized protection on mucosal surfaces Esp effective against microorganisms and agglutinating antigens, 1 st Ab produced in initial infection Opsonin (enhances phagocytosis) neutralizes toxins and viruses, protect fetus and newborn Known functions No No No No Yes Placental transfer NO No No yes yes Complement fixation 190,000 175,000 405,000 970,000 150,000 Mol Wt Bound to mast cells and basophil throughout body, blood B cell surface, blood lymph Secretions (tears, saliva, mucus, intestine, milk) blood, lymph Blood, Lymph, B cell surface Blood, lymph, intestine Location 0.002% 0.2% 10-15% 5-10% 80% % total serum Ab monomer monomer Dimer Pentamer monomer Structure IgE IgD IgA IgM IgG CHARACTERISTICS

Figure 12-8 The classical, lectin, and alternate complement pathways. Despite different activators, the goal of these pathways is cleavage of C3 and C5 to provide chemoattractants and anaphylotoxins (C3a, C5a), an opsonin (C3b) that adheres to membranes, and to initiate the membrane attack complex to kill cells. MASP, MBP-associated serine protease; MBP, mannose-binding protein. (Redrawn from Rosenthal KS, Tan JS: Rapid review microbiology and immunology, St. Louis, 2002, Mosby.) Downloaded from: StudentConsult (on 23 September 2006 05:04 AM) © 2005 Elsevier

Biologic Activities of Complement
Cytolysis - MAC
Opsonization – C3b
Chemotaxis – C5a
Anaphylatoxin –C5a, C3a
Increased vascular permeability
Smooth muscle contraction
Degranulation of mast cells

HYPERSENSITIVITY Tuberculin rxn, TB, leprosy, contact dermatitis TH1-Ag complex----> lymphokine release ---> activated macrophage---> tissue injury. CD8+ Tcell cytotoxicity TH1(CD4+), lymphokines, CD8+ Tcell IV. Delayed Type Arthus rxn; Farmer’s lung; Serum sickness; AGN; rheumatoid arthritis Soluble Ag-Ab complex: Platelet aggregation Release of anaphylatoxin, chemotactic factors (for neutrophils) IgG or IgM, Complement III. Immune Complex type Transfusion reaction, HDN, hemolytic anemia, Good Pasture’s syndrome, Myathenia gravis Cellular Ag-Ab complex; Complement activated; Cytolysis ADCC Opsonization IgG or IgM, Complement, K cell II. Cytotoxic Type Urticaria Asthma Food allergy Penicillin allergy Atopic dermatitis Bee sting Allergen crosslinks IgE Attached to mast cell; Degranulation, release of histamine and other vasoactive amines IgE Mast cells vasoactive amines I. Anaphylactic type Example Mechanism Primary Mediators Type

Figure 14-11 Type I hypersensitivity: immunoglobulin E (IgE)- mediated atopic and anaphylactic reactions. IgE produced in response to the initial challenge binds to Fc receptors on mast cells and basophils. Allergen binding to the cell surface IgE promotes the release of histamine and prostaglandins from granules to produce symptoms. Examples are hay fever, asthma, penicillin allergy, and reaction to bee stings. IL, Interleukin. Downloaded from: StudentConsult (on 23 September 2006 05:04 AM) © 2005 Elsevier

Figure 14-12 Type II hypersensitivity: mediated by antibody and complement. Complement activation promotes direct cell damage through the complement cascade and by the activation of effector cells. Examples are Goodpasture's syndrome, the response to Rh factor in newborns, and autoimmune endocrinopathies. ADCC, Antibody-dependent cellular cytotoxicity; Ig, immunoglobulin. Downloaded from: StudentConsult (on 23 September 2006 05:04 AM) © 2005 Elsevier

Questions 1-6
(A) T cells
(B) B cells
(C) Macrophages
(D) B cells and macrophages
(E) T cells, B cells, and macrophages
Major source of interleukin-1
Acted on by interleukin-1
Major source of interleukin-2
Express class I MHC markers
Express class II MHC markers
Express surface immunoglobulin

(A) Class I MHC proteins
(B) Class II MHC proteins
1. Involved in the presentation of antigen to CD4-positive cells
2. Involved in the presentation of antigen to CD8-positive cells
3. Involved in antibody responses to T-dependent antigens
4. Involved in target cell recognition by cytotoxic T cells

Which are both opsonins?
A. IgG and IgA D. IgA and C3a
B. C3b andC3a E. IgA and C3b
C. IgG and C3b
The rapid rise , elevated level and prolonged production of antibody that follows second exposure to antigen is known as
A. Delayed hypersensitivity reaction
B. Anamnestic response
C. Autoimmune reaction
D. Thymus-independent response

C3 is cleaved to form C3a and C3b by C3 convertase. C3b is involved in all of the following EXCEPT:
A. altering vascular permeability
B. promoting phagocytosis
C. forming alternative-pathway C3 convertase
D. forming C5 convertase

You have a patient who makes autoantibodies against his own red blood cells, leading to hemolysis. Which one of the following mechanisms is MOST likely to explain the hemolysis?
A. Perforins from cytotoxic T cells lyse the red cells
B. Neutrophils release proteases that lyse the red cells
C. Interleukin-2 binds to its receptor on the red cells, which results in lysis of the red cells
D. Complement is activated, and membrane attack complexes lyse the red cells

Your patient became ill 10 days ago with a viral disease. Laboratory examination reveals that the patient's antibodies against this virus have a high ratio of IgM to IgG. What is your conclusion?
A. It is unlikely that the patient has encountered this organism previously
B. The patient is predisposed to IgE-mediated hypersensitivity reactions
C. The information given is irrelevant to previous antigen exposure
D. It is likely that the patient has an autoimmune disease

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Basic Microbiology

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