Microbiology

1. Microbiology
Definition
Branch of biology that deals with the smallest living
organisms, which cannot be seen by naked human eye.
Branches of Microbiology
Bacteriology
Virology
Mycology
Parasitology

2. Bacteriology - Study of Bacteria - the smallest, simplest
single-celled organisms.
Virology - Study of Viruses - minute and ultrasmall
unicellular particles
Mycology - Study of Fungi
Parasitology - Study of protozoa and helminths (worms)

3. Classification of micro-organisms
Definition Organisms without a nuclear Organisms with a nuclear
membrane surrounding the genetic membrane surrounding the
material genetic material
The micro-organisms are broadly classified into Prokaryotes and
Eukarytoes
Prokaryotes Eukaryotes

4. Nucleus Prokaryotic None Eukaryotic Eukaryotic
Nucleic Acid Both RNA & Either RNA & Both RNA & Both RNA &
DNA DNA DNA DNA
Replication Binary No Binary Binary Binary
Fission Fission Fission Fission &
Budding
Motility Some None None Most
Distinguishing Features of Bacteria, Viruses,
Fungi and Parasites
Features Bacteria Viruses Fungi Parasites

5. Methods that the help the microbiologist to
classify bacteria
Bacterial shape eg. coccus, bacillus
Gram stain eg. gram (+)ve, gram (-)ve
Oxygen requirement eg aerobe, anaerobe
pH eg. Acidophilic
Pathogenicity eg. commensal, pathogen
Drug susceptibility eg. sensitive, resistant

6. Shape of the Bacteria
Bacteria Shape & Feature
Coccus Spherical or dot-like
Bacillus Cylindrical or rodlike. Differ considerably in length
& diameter. Some are slennder, some rectangular
with squared ends and some shaped like clubs.
Coccobacilli Very short (stubby) bacillus
Vibrio Coma shaped bacillus which vibrate
Spirillum Helix-shaped and curved, high degree of motility
characterized by corkscrew movement
Spirochaete Another type of spiral-shaped bacteria, having as
many as 20 coils

7. Shape of the Bacteria

8. Gram Staining
Gram positive (Purple)
Gram Stain
Gram negative (Pink)

9. Differential stains
Gram stain
Gram positive (Purple)
Gram negative (Pink)
Gram Staining

10. Bacterial Cell

11. Bacterial anatomy
All bacteria are prokaryotes and hence they possess the
same anatomy.
I. cell envelope → It has two components
Cell wall
Cell membrane
a) Cell wall
This is the outermost covering of the bacterium which
prevents the cell from bursting.

12. Bacterial anatomy
Cell Wall Structure :
Cell Wall Component: Gram Positive Bacteria Gram Negative Bacteria
Peptidoglycan Thick layer Small amounts
Teichoic acids Yes (has) none
Lipopolysaccarides Small amount Large amount (endotoxin!)
Periplasmic space absent Present

14. Functions of Cell-Wall
Provides shape to bacterium.
Gives rigidity to organism.
Protects from environment.
Contains components toxic to host.

15. Atypical Cell Walls
Genus Mycoplasma → no cell walls. Antibiotics like
penicillins that interfere with the cell wall assembly are not
helpful in treating this infection
b) Cell Membrane
The boundary layer of the cytoplasm that lies just beneath the
cell-wall. Primarily it allows nutrients to pass inside the cell
and waste products out of the cell.

16. II Cytoplasm
A gelatin substance bound by cell-membrane.
III Nucleoid
The nuclear region that contains the genetic material of a cell.
A single, circular, double stranded DNA (Deoxyribonucleic acid)
molecule without a nuclear membrane
IV Ribosomes
Small cytoplasmic particles, the sites of PROTEIN SYNTHESIS.

17. V Capsule
It is outermost (outside cells wall) gelatinous layer of
polysaccharides and proteins secreted by many bacteria.
Function :- to avoid phagocytosis (ingestion of microorganism
by the cell called phagocyte)
VI Flagella
Long strands of protein that enable many species of bacteria to
move by rotating.

18. VII PILI
Bristlelike appendages primarily found in gram (-ve) bacteria that
extend from cell membrane. ‘Common pili help bacteria to adhere to
different surfaces thereby enhancing their ability to cause disease.’
Sex pili aid in the transfer of DNA among bacteria. (conjugation)
VIII Endospores
Formed inside the parent cell. A highly resistant stage of bacteria very
difficult to kill the bacteria in this stage.
IX Periplasmic Space
The region between the inner and outer membranes of gram negative
bacterial cell.

19. Growth and multiplication of bacteria
Binary Fission
Bacteria divide by binary fission. Cell divide approximately
evenly into two daughter cells, without exchange of
genetic material between two cells.
Cell wall Septum Cytoplasm

20. Bacteria Nutrition
a) Oxygen
Micro aerophlic grow best in the presence of low O2 tension
Depending on the influence of oxygen
Aerobes Anaerboes
Require O2 for growth Obligate Facultative
Obligate aerobes
Grow only in the presence of O2
eg. Vibrio cholerae
Grow only in the
absence of O2
Ordinarily aerobic
but also grow in
the absence of O2

21. b) Carbon dioxide :
Bacteria require small amounts of carbon dioxide
Capno-philic:
Much higher levels of CO2 for growth
c) Temperature
‘Optimum temperature' in case of most of the pathogenic
bacteria = 37o
c

22. d) Moisture :
e) pH :
Optimum pH = 7.2-7.6
Acidophilic bacteria:
Grow under acidic conditions eg. Lactobacillus
(Vibrio cholerae tolerates high degree of alkalinity)

23. GRAM POSITIVE
Gram-positive Aerobic Cocci (SSP)
•Streptococcus pneumoniae
•Streptococcus pyogenes
•Streptococcus viridans
•Staphylococcus aureus
•Staphylococcus epidermidis
•Pneumococcus
Gram-positive Aerobic Bacilli (CD)
•Corynebacterium diphtheriae

24. GRAM NEGATIVE
Gram-negative Aerobic Cocci (MNN)
Moraxella catarrhalis
Neisseria gonorrhoeae
Neisseria meningitidis
Gram-negative Aerobic Bacilli (KEPS, HI, HD, VC)
Klebsiella pneumoniae
E. coli
Enterobacter spp.
Psuedomonas aeruginosa
Proteus
S.TYPHI
Shigella
H. influenzae
Haemophilus ducreyi
Vibrio cholerae

25. ANAEROBESGram-positive Anaerobic Cocci (EP)
Enterococcus (S. faecalis)
Peptococcus
Peptostreptococcus
Gram-negative Anaerobic Cocci (V)
Veillonella
Gram-positive Anaerobic Bacilli (4CL)
Clostridium perfringes
Clostridium tetani
Clostridium difficile
Clostridium welchii
Gram-negative Anaerobic Bacilli (FBP)
Fusobacterium
Bacteriodes
Prevotella
Gardnerella Vaginalis

26. ATYPICAL BACTERIA
(LCM UCM)
Legionella pneumuphilla
Chlamydia pneumoniae
Mycoplasma pneumoniae
Ureaplasma urealyticum
Chlamydia trachomatis
Mycoplasma hominis

27. SOME COMMON TERMS AND THEIR
DEFINITIONS
PATHOGEN
The term pathogen most commonly is used to refer to infectious organisms. These include bacteria,
protozoa, viruses and fungi. The term pathogen was devised about 1880 and was compounded from patho-
meaning disease + -gen indicating a producer. Hence, a disease producer
HOST
An organism or cell culture in which a PATHHOGEN can replicate itself.
INFECTION
An infection is the colonization of a host organism by pathogens
COLONIZATION
Colonization occurs whenever any one or more pathogens populate an area.

28. SOME COMMON TERMS AND THEIR
DEFINITIONS
1.PRIMARY INFECTIONS :
It is an initial infection for which the patient is been treated by the physician
2.SECONDARY INFECTIONS :
It occurs during the treatment of primary infection, if the individual develops another
infection in some other system / organ.
3.SUPERINFECTION :
Antibacterial treatment may sometimes destroy the normal intestinal flora. This
weakens the defense in immune system. At the point of time the facultative
organisms may invade and cause a Super infection.
5.CROSS INFECTIONS :
When a new infection sets from another host in a previously infected patient.

29. Skin (Intact) Dryness (Keratinized), Wounds, excess moisture
acid pH microbial flora of skin,
(sweat etc.), serous discharge constant shedding
Eye Tears contain the enzyme Dryness of the eye, altered
lysozyme lysozyme which lyses bacteria
Host Defence Mechanisms
Non-specific immunity of a human being. The one which does
not care nor remember, the type of microbes invading the body.
Body Site Defence Conditions that
Mechanism encourage entry

30. Respiratory Mucous and ciliated cells Reduced movement of
tract constantly move mucous mucous trapped particles and
trapped particles and microorganisms by cilia as
microorganisms to throat. in smoking, viral infection etc.
Coughing, Sneezing
Gastrointestinal The highly acidic pH (1.5) Reduced stomach acid
Tract of stomach secretions, (achlorhydria) and raising of it's
enzyme Pepsin pH by regular ingestion of
antacids.
Host Defence Mechanisms
Body Site Defence Conditions that
Mechanism encourage entry

31. Urethra & Vagina Flushing action of urine & Reduced members of
Acidic pH of vaginal Lactobacilli and other vaginal
secretions promoting the flora from douching, soaps
growth of Lactobacilli- menopause, Antibiotic therapy,
(Non-pathogenic) during Short Urethra, sexual
child bearing age. intercourse with carrier
partner
Host Defence Mechanisms
Body Site Defence Conditions that
Mechanism encourage entry

32. Normal microbial flora of the human body
Prevent or interfere with the colonization or invasion of the body by
pathogens
Raise the overall immune status of the host against pathogens. But may
cause confusion in diagnosis
The normal flora of the body
Body site Normal flora
Skin Staphylococcus, Streptococcus faecalis, viridans
E.Coli, Candida
Conjunctiva Corynebacterium xerosis, staphylococcus
Upper respiratory tract Staphylococcus, streptococcus, haemophilius,
E.coli, proteus
Intestinal tract Lactobacillus, anaerobic, streptococci, bacteroides,
clostridia, E.coli, proteus, candida
Genitourinary tract Mycobacterium smegmatis, Streptococci, candida,
staphyloccus epidermides

33. Infections & Causative Pathogens
Meningitis (Adults) - Neisseria meningitidis, Haemophilus.
influenzae, Streptococcus pneumoniae.
(Neonates) - Escherechia coli, streptococcus,
Listeria monocytogenes.
Brain Abscess - Staphylococcus aureus,
Staphylococcus epidermidis,
Streptococcus pyogenes,
Enterobacteriaceae, Bacterioides fragilis.
URTI (Upper respiratory - Streptococcus pyogenes,
Haemophilus
tract infection) influenzae, Stapyloccus pneumoniae,
M. catarrhalis.
LRTI (Hospital acquired) - Klebsiella, Haemophilus influenzae,

34. Infections & Causative Pathogens
LRTI (Hospital acquired) - Klebsiella, Haemophilus influenzae,
Pseudomonas, Escherechia coli,
Streptoccus pneumoniae,
Staphylococcus aureus, Bacteroides
fragilis.
(Community acquired) - Streptococcus pneumoniae,
Haemophinus influenzae, Klebsiella,
M. catarrhalis, Legionella, Mycoplasma,
Chlamydia.
G.I.T.I. (Gastrointestinal tract - Escherachia coli, Salmonella,
Shigella,
infection Campylobacter, Enterobacter.

35. Infections & Causative Pathogens
U.T.I. (Urinary tract infection) - Escherachia coli, Proteus, Klebsiella,
Pseudomonas, Citrobacter, Serratia,
Morganella, Neisseria, Chlamydia,
Staphylococcus saprophyticus
PID (pelvic inflammatory - Escherachia coli, Staphylococcus
aureus,
disease) Neisseria gonorrhoeae, Chlamydia,
Bacteroides fragilis, Proteus Pseudomonas.
Bone and Joint Infection - Staphyloccous aureus, Strptococcus
epidermidis,

37. Antimicrobials
An antimicrobial is the drug that kills (or inhibits the
multiplication of) microorganisms.
An antibiotic is a type of antimicrobial that is
produced by microbes and is harmful to other
microbes.
An antibacterial is the antibiotic used to inhibit or
kill bacteria.

39. Antibacterial Drugs
Mechanism Why antibacterials do not Examples
affect human and animal cell?
Damage cell membrane, High toxicity to animals and Polymixins
allow contents to leak out humans. Topical use only
(Bactericidal)
Inhibits cell wall synthesis Animals and humans do not Penicillins
(Bactericidal) have cell wall hence are not Cephalosporins
affected Vancomycin
Inhibitors of folic acid Animals and humans get folic Sulfonamides
synthesis (need this to acid from diet (do not Trimethoprim
make DNA for growth synthesize it) Co-trimoxazole
and multiplicaction.)

40. Antibacterial Drugs
Inhibitors of DNA function Drugs used affect Quinolone, metronidazole
need DNA cell growth bacterial/fungal cells more Rifampicin
than animal and human cells
Inhibitors of protein High doses of drugs can Tetracycline
synthesis0 Proteins are affect animals and humans Aminoglycosides
synthesized in cell structure because some ribosome are Chloramphenicol
called ribosome's and these similar to those in bacteria Macrolides
are different in bacteria and
human

41. Antibiotic resistance
There are different mechanisms for development of resistance
1) Production of bacterial enzymes which can destroy the antibiotic
eg. Beta lactamases from staphylococci acting on penicillins and
cephalopsorins.
2) Altering targetsite (Binding protein)
Aleteration in the methicillin binding protein of staphyloccocus leading
to methilillin
resistant Staphylococcus aureus (MRSA)
3) Changing the permeability of cell walls to inhibit entry of antibiotic in
bacterial cell.
4) Expelling out the antibiotic by a pump mechanism (rare mechanism)
5) Lastly, the widespread and inappropriate use of antibiotics contributes
to the development of at least some type of resistance.

42. General Properties of Viruses
Viruses are obligate intracellular parasites
No cellular organisation
Contain only one type of nucleic acid either DNA or RNA,
never both
Dependent on the host cell for their multiplication
They do not multiply by binary fission but by some
complex mechanism
Unaffected by antibacterial antibiotics

43. Mycology
Fungi are eukaryotes
They have a cell wall and typical cell organelles
Nucleus contains double standed DNA
They are unicellular or multicellular
They divide by budding
Moulds - Filamentous fungi
Dimorphic fungi - fungi occuring in round cell form as well as
filamentous form
Mycelium - Mass of hyphae

44. Parasitology
Parasite : An animal /plant which lives in or upon another
organism (technically called as host) and draws its
nutrients directly from it
Host : An organisms which harbors the parasite and
provides the nourishment and shelter
Parasitology : Study of protoza and helminths
Protozoa : single celled parasite
Helminths : (Helminth =Worm) multicellular, elogated flat/
round bodies.

45. Trophozoite Cyst
Actively motile non motile
Parasite can acquire their Cannot acquire their
nutrition in this stage nutrition in this stage
Gets affected easily by Does not get affected
outside environment by outside environment
(Resistant-stage)
Pseudopodia (False foot)
Ectoplasm
Nucleas
Endoplasm
Thick cystcoal
Nucleus
Protozoa : Can Exists in two Forms