notes

1. MICROBIOLOGY
GENERAL MICROBIOLOGY
 Bacteria were discovered by Anton von Leeuwenhoek, who named them
animalcules.
 Obligate anaerobes: These grow only under conditions of high reducing
intensity. These bacteria lack catalase, peroxidase, superoxide dismutase and
cytochrome systems. Examples for obligate anaerobes are Clostridium and
Bacteroides.
 Facultative anaerobes: These can grow under both aerobic and anaerobic
conditions. Examples of facultative anaerobes are enterobacteriaceae
family etc.
 Obligatory aerobes: These cannot grow unless oxygen is present in the
medium. Examples of obligatory aerobes—Pseudomonas.
 Microaerophillic: These organisms can grow under conditions with low
oxygen tension. Examples of microaerophillic are Clostridium tetani
species.
 Chemoheterotrophs—these bacteria grow only if a source of organic
material as a nutrient is available.
 Optimum temperature for psychrophillics is 10-20°C, mesophilics 25-40°C,
and thermophilics 50-60°C.
 Redox potential of most aerobes +0.2 to 0.4 volt. Redox potential for
anaerobes is0.2volt.
 Plasma membrane acts as an osmotic barrier in bacterium.
CELL WALL
 Function:
o gives shape and protects bacteria from antibacterial drugs.

2. o Demonstrated by plasmolysis.
o Made of N-acetyl
o muramic acid and galactosamine.
 Flagella:Organ of mobility
o 10 to 30 nm diameter.
o Situated external to cell and attached to cell surface.
o Made of protein, are antigenic but not protective.
o Peritrichous Flagella all around the cell. Ex: S.typhi
o Monotrichous Flagella at one end. Ex: Vibrio.
o Lophotrichous Flagella in tufts.Ex: spirilla
o Amphitrichous Flagella at both ends.
 Pili/fimbriae:
o Organ of adhesion and conjugation.
o Originate in cell membrane.
o Seen in gram negative bacilli.
o Are antigenic and detected by haemagglutination.
o Gram +ve bacterium having pili is Corynebacterium diphtheriae.
o Ex: E. coli & Bacillus
 Spore:
o Protective in function. Most resistant forms.
o Formed when nutritional conditions are unfavourable.
o ZeilNeelsen technique for acidfast spores.
o Stained by malachite green and carbol fuschin.
o Destroyed by autoclaving.
o Spores—seen in Bacillus and Clostridium.
 Bacterium contains a single circular double stranded DNA.

3.  Extra chromosomal structures present in bacteria are plasmids and
episomes.
 Plasmids—responsible for toxicity and drug resistance. It is extra
chromosomal genetic material capable of self replication.
 Acquired by transduction.
 Episomes are extra chromosomal genetic material incapable of
selfreplication.
 Mesosomes/chondroids—equivalent to mitochondria. Helps in respiration.
Formed by involution of cytoplasmic membrane.
 Volutin/metachromatic/BabesErnst granules—seen in Corynebacterium
diptheriae. Stained by Albert's stain. Also known as polymetaphosphate
bodies.
 Generation time—is the time required for completion of one bacterial life
cycle. Normally it is 15 minutes in vegetative bacteria.
o Coliform bacilli—20min
o Tubercle bacilli—20 hr
o Lepra—20 days
 The growth curve of bacteria consists of log phase, lag phase, stationary and
decline phases.
 Lag phase—adaptation of bacteria to new environment.
 Stationary—birth rate equals death rate.
 Phase of decline—death rate exceeds and so decline in total number of
organisms.
 Capability of microbes causing diseases is called as pathogenicity.
 The degree of pathogenicity is called virulence. Enhancement of virulence is
exaltation and decrease is attenuation.

4.  Koch's postulates:
o Microorganism should be found in all cases of infection.
o Microorganism should be grown in pure culture in vitro for several
generations.
o Such pure culture, when inoculated into a susceptible animal, should
result in typical disease.
o Microorganism should be recovered from such infected animal.
 Differences between exotoxin and endotoxin:

 Toxoid = Formaldehyde + Exotoxin
 Nontoxic Can induce antibody formation
BACTERIAL GENETICS
 Methods of genes transfer can be transformation, transduction and
conjugation.
 Transformation—is the transfer of genetic material through the agency of
free DNA. Ex: Bacillus, Haemophilus, Pneumococcus.
 Transduction—is the transfer of a portion of DNA from one bacterium to
another by means of a bacteriophage. This has been proposed as a method of

5. genetic engineering and in the treatment of born errors in metabolism.
Involves Chromosomal DNA, plasmid and episomes.
 Conjugation—is gene transfer occurring when there is a mating between
cells in contact. Male of donor bacteria with the plasmid DNA joins the
female/ recipient bacteria through the conjugation tube and converts it to
male bacteria by passing the DNA through the conjugation tube.
 Plasmid that gives the bacteria ability to undergo conjugation is known as
the fertility factor/Ffactor/ transfer factor.
 This contains the genetic information for sex pilus.
 Acquisition of new property by a bacterium when it is lysogenized by
bacteriophage is called phage/lysogenic conversion. Examples:
Corynebacterium diphtheriae—beta phage.
 Resistance transfer factor (RTF)—Plasmids are responsible for resistance
transfer.
 Mechanism of drug resistance
o Mutation—one step or step wise mutations.
o Alternative metabolism—Sulphonamides.
o Inactivating enzymes—Penicillins.
o Decreased permeability to the drug—Gentamycin.
o Change in receptor—Tetracycline, Gentamycin.
 AME test is a test for mutagenicity.
 Bacterial arrangements:
o Anthrax -Chains/bamboo stick appearance
o Diphtheria- Chinese letter pattern
o Enterococci -Pairs
o Leprosy- Cigar bundle arrangement

6. o Meningococci/gonococci- Pairs—intracellular
o Pneumococci- Pairs
o Staphylococci -Bunches/irregular
o Streptococci- Chains
CULTURE MEDIA
Classification
 Simple media—consists of peptone, meat extract, NaCl and water. Ex:
Nutrient broth, nutrient agar.
 Indicator/differential media—culture media demonstrating a particular
metabolic characteristic identification media/indicator media. Ex:
WilsonBlair media for salmonella and potassium tellurite media for
diphtheria.
 Selective media—culture media stimulate few types of bacterial growth.
Example for anaerobic media: thioglycollate, Robertson meat medium.
 Enriched medium—contain growthpromoting ingredients. Blood, serum,
agar are added to simple media. Examples are blood agar, chocolate agar.
 Enrichment medium—substance added either to inhibit unrequired bacteria
or to stimulate desired bacteria. Ex: tetrathionate broth »inhibits E.coli and
stimulates growth of typhoid; selenite F broth.
 Differential media—brings about special characteristics. Ex: McConkey
media for lactose fermenters. Naegler's reaction for lecithinase activity.
 Transport media—Ex: Stuart's media, Pikes medium
 Concentration of blood used for blood agar medium is 10%.
 Methods of culturing microorganisms

7. Culture method Use
1. Streak culture Isolation of bacteria in pure form
2. Lawn/Carpet culture Bacteriophage typing & antibiotic sensitivity testing
3. Stroke culture Pure growth for slide agglutination
4. Stab culture For demonstrating gelatin liquefaction &
a. oxygen requirement by bacteria
5. Pour plate culture Estimation of viable count
6. Sweep plate method Estimation of bacteria in dust/clothing
 Anaerobic culture methods:
i.Alkaline pyragallol—absorbs oxygen.
ii. Rosenthal method—Chromium + sulphuric acid in jar.
iii. Mcintosh and Filde's jar uses palladenised asbestos as catalyst
iv. Gaspack on addition of water gives hydrogen and carbon dioxide gas,
thus utilizes the oxygen,
v. Use of reducing agent Ex: 1% glucose, 0.1% thioglycollate.
vi. Anaerobic cabinet most reliable.
 Selective media - Microorganism
o Naguchi's medium- Borellia
o Robertson's cooked meat media -Clostridia
o Loeffler's serum slope- Corynebacterium
o Sabourad's dextrose agar -Fungi
o 8-10% NaCI Tellurite medium -Staphylococci
o LowensteinJensen Media -Myco.tuberculosis
o Pikes media- Transport medium for streptococci

8. BACTERIAL STAINING:
 Staining that kills microorganisms is supravital staining, and that which
doesn't is intravital staining.
 Gram stain—based on content of cell wall—some retain crystal violet even
after addition of decolourizing agent (+ve).
 Based on para rosaniline dye system. .
 Primary stain—crystal/gentian/methyl violet, e. Secondary stain—
safranine/carbol fuschin
 Gram+ve—violet stained, as they resist decolonisation*
 Gram-ve—reddish pink.
 Acidfast bacilli—ZiehlNeelsen staining— those organisms that retain
carbol fuschin (red) when decolourized with 35 HCl or 20% H2S04. Ex:
Nocardia, Mycobacterium.
 These bacteria are acidfast as cell wall contains mycolic acid and due to cell
wall integrity.
 Negative staining:
o Staining of background with acidic dye.
o Dyes used are Nigrosin, Indian ink.
o Ex: Spirochetes, bacterial and fungal capsule.
 Albert's stain to demonstrate granules in Corynebacterium diphtheriae.
 Giemsa stain is used to stain spirochetes.
 Feulgen stain is specific for DNA (nuclei).
 Prussian blue test—haemosiderin.

9. STERILISATION AND DISINFECTION
 Sterilisation: removal of all microorganisms either in the vegetative or
spore state.
 Disinfection: removal of all pathogenic organisms, but not spores on
inanimate surfaces.
 Asepsis: removal of all pathogenic organisms form animate surfaces.
 Methods of sterilisation:
 Sunlight presence of UV rays.
 Heat:
 Dry heat by protein denaturation, oxidative damage, and elevated
electrolyte concentration.
o Red heating wires.
o Flaming loop,
o tips of forceps.
o Incineration soiled
o dressings, animal carcasses, pathological material.
 Hot air oven:
 Holding period—15 lb 160°C for 1 hour.
 Used for glassware,powders, oils and greases.
 Moist heat—kills microorganisms by denaturation of proteins and
coagulation.
 Temperature below 100°C-
i. Pasteurizationmilk-. Holder method 63°C/30min . Flash method
72°C/22 sec.
ii. Inspissator:¦80-85°C for 1 hr on 3 consecutive days.
Ex: LJ media, Loeffler's serum.

10.  Temperature at 100°C
o Boiling cystoscopes,specula.
o Steam at atmospheric pressure (100°C)
o Used for media that decomposes at high temperature.
o Holding period 90 minutes.
iii Tyndallisation for media containing sugar gelatin 100°C for 20 min.on 3
successive days.
 Steam under pressure (>100°C)
Autoclave:Holding period — 121 °C (250°F) for 15 min under 15 psi
pressure. Uses dressings,instruments, media.
c. Filtration:
o Use antibiotic solution, sera, carbohydrate solution.
o Earthenware Keiselgurh type and porcelain type.
o Asbestos Seitz filter.
o Sintered glass filter
o Membrane filter, cellulose acetate and gradocol membrane.
d. Radiation- syringes,wards and OR, plastic material, culture, catheters.
o Nonionising:Infrared, UV rays.
o Ionising (Cold Sterilisation) :Xrays, gamma rays.
e. Chemical -kill microorganisms by protein denaturation, disruption of cell
membrane and removal of free sulphydryl groups.
o Alcohol , Ethyl Alcohol- skin antiseptic ( 60-70%)
o Isopropyl alcohol- thermometer.
o Methyl alcohol fungal spores. Alcohol is not sporicidal.
o Aldehyde preservation of anatomical specimen, fumigation etc.
o 2% Glutaraldehyde is viridical, sporicidal and
bactericidal.Endotracheal tube, mask, rubber tubing.

11.  Dyes:
o Aniline malachite,crystal violet.
o AcridineAcriflavin, Proflavin.
o Phenol acts by damaging the cell membrane. Ex: Lysol, cresol,
chlorhexidene.
 Gas:
o Ethylene oxide acts by alkylation of DNA and RNA. High penetrating
power and diffuses through plastic. Ex: suture material, disposable
single use devices.
o Formaldehyde OT fumigation using 37% by weight in water.
o Betapropiolactone product of ketone and formaldehyde. Active
against virus.
 Surface active agents:
(a)Cationic surface active agents:
 Act on phosphate group of cell membrane. Better against gram positive
microorganisms.
 No action on spores.
 Ex: QUATS Benzalkonium chloride, eetavolon, cetrimide.
(b). Anionic agents—act on gram negative microorganisms. Ex: Common
soaps.
 Phenol coefficient test is used in evaluating capacity of disinfectant.
 Salmonella typhosa is used to detect phenol coefficient test.
 Chlorhexidine acts by adsorbing tooth surface.
 Endoscopes are sterilized by Cidex liquid.
 Glass syringes are best sterilized by gamma rays.
 Dettol—Chloroxylenol;

12.  Savlon—Cetrimide.
 Chemicals active against hepatitis B virus—gluteraldehyde, hypochlorite,
formaldehyde.
 Chemicals active against HIV virus—1% sodium hypochlorite,2%
gluteraldehyde, 6% hydrogen peroxide.
IMMUNITY
 Primary lymphoid organs—thymus and bone marrow.
 Secondary lymphoid organs—lymph nodes, spleen, gut associated
lymphoid tissue, appendix, tonsils and adenoids.
 Natural immunity—not acquired by contact with an antigen.
 Is nonspecific and is provided by skin, natural killer cells, phagocytosis,
interferon, inflammation.
 Acquired immunity:

13. Vaccines:
 Bacterial live vaccine—BCG vaccine.
 Bacterial killed vaccine—TAB vaccine.
 Viral live vaccine—Sabine vaccine (oral polio vaccine [OPV]).
 Viral killed vaccine—Salk vaccine.
 Premunition is seen in syphilis.
 The only condition where post exposure vaccines are used is rabies.
 A special type of immunity attained by injecting immunological competent
lymphocytes—adoptive immunity.
 T-Lymphocytes consist of regulatory (T4,T8) and effector cells.
 HLA complex is located in human beings in short arm of chromosome 6.

14.  Major histocompatibility complex (MHC):
— MHC class I—seen in all nucleated cells.
— MHC Class II—seen on macrophages (CD4), dendritic cells, B and
T lymphocytes.
 Antigen presentation—ClassII MHC.
 Immunodeficiency manifests only after 6 months of age due to protection by
maternal antibodies.
 Interferons are stored at 4°C.
Antigen and Antibodies
 Antibodies—are chemically glycoproteins and are members of gamma
globulin class of plasma proteins.
 Antigen is multivalent but antibody is bivalent, immogenic.
 All proteins are antigenic except gelatin.
 Immunoglobulins—are classified based on the heavy chain. Have two
sites:
o Amino terminus—binding site of antigen.
o Carboxy terminus—determines complement fixation and placental
transfer.
 Light and heavy chains in immunoglobulins are held together by disulphide
bonds.
 Adjuvant—potentiate the immune response.
 Immunoglobulin G—maximum in concentration of serum, crosses
placental barrier. Distributed equally in extra and intravascular
compartments. Fixes complement. Provides passive immunity to newborn.
Known as warm antigen.

15.  Immunoglobulin A—appears in exocrine secretions, present on the
membrane, stimulates complement pathway alternatively. Secretory
 IgA is dimer with J chain. Known as antibiotic paint of the body.
 Immunoglobulin E—reagin antibody, mainly seen in allergic parasitic
infections and anaphylactic conditions. Secreted in alimentary and
respiratory tract. Plays role in anaphylaxis. Heat labile.
 IgM—known as millionaire Ig. Formed as earliest/initial response. Present
only in intravascular compartment. Capable of fixing complement. Known
as cold antigen. Plays role in opsonisation.
 Hapten—not capable of inducing antibody formation independently but
react with antibodies.
 Epitope—Smallest unit of antigenicity. Has specific chemical structures and
spatial configuration.
 Paratope—Region of antibody that combines with epitope.


16.  Important aspects of lg:
o Ig for autoimmune reactions- IgM
o Maximum in secretions and mucosal- IgA
o Ig prevents adhesion to mucosa -IgA
o Ig in milk- IgA & IgG
o Maximum in sulcular fluid -IgG
o Most abundant and smallest -IgG
o Ig crossing placenta- IgG
o Warm antibody- IgG
o Cold antibody -IgM
o Blocking antibody- IgG
o Secreted by Gram +ve bacteria- IgG
o Secreted by Gram ve bacteria -IgM
o Largest Ig- IgM
o First Ab to initial Ag exposure- IgM
o Earliest Ig to be synthesized IgM
o Natural Ig to ABO blood gp Ag -IgM
o Intravascular Ig -IgM
o Reagenic/Allergic Ig (atopy, anaphylaxis)- IgE
o Heat labiLe -IgE
o Minimum halflife- IgE
o Immediate hypersensitivity- IgE
 Ring/tube precipitation test—Lancefield grouping of streptococci.

17.  Antibiotic precipitation test—slide precipitation test—single diffusion in 2
dimensions.
 VDRL test—slide flocculation test.
 Kahn test—tube flocculation test.
 Widal—tube agglutination.
 Cross matching—slide agglutination test.
 Latex agglutination—detection of HBs Ag, ASO, and CRP (creactive
 protein).
 Mantoux test is negative in kwashiorkar.
 Coombs test, PaulBunnel test, WeilFelix test—Agglutination test.
 Passive Coombs test—RoseWaaler test for rheumatoid arthritis.
 Coombs test—for identification of Rh antigen of fetus..
 Treponema pallidum immobilisation test and Wassermann test—
complement fixation test.

18.  Hypersensitivity (Allergy)
 Classical complement pathway can be stimulated by IgG, IgM, and
alternative pathway by IgA.
 State of reduced/absent responsiveness to an immunogen that would
ordinarily make a response is called immunological tolerance.
 Hapten—partial antigen—unable to stimulate antibody formation unless it
attaches to carrier molecule.
 Complement system—known so as it complements antibody in its action.
Consists of pathway consisting of 11 proteins—C1 to C9.
 C1—calcium dependent.
 Classical complement pathway is activated at C1.

19.  Alternative complement pathway is activated at C3 where the activator is
zymosan.
 Primary response (humoral)—is detectable in about 3-5days; increase
until they reach peak in about 10-14 days, then decreases.
 Secondary response—begins within minutes, reaches maximum intensity
after 10-20 minutes and subsides over a period about 1 hour.

 Opsonin (C3b, Fc part of IgG)—antibody that attaches to bacterium and
facilitates phagocytosis of those bacteria.
 Diagnostic tests involving complement system include: Treponema pallidum
immobilisation test (TPI), Wassermann test for syphilis.
 Most strong immunogenic antigen among Rh allele genes is D.

20.  AntiRh antibodies are mainly IgG.
 Blood typing is based on agglutination reaction.
 A +ve is the commonest blood group (40%).
 O ve is called universal donor.
 AB +ve is the least common blood group (5%). It is called universal
recipient.
 Various types of grafts:
a) Homograft- Same species
b) Heterograft- Different species
c) Isograft- Same genetic composition individual (twins)
d) Autograft- Same person
e) Allograft -Other person
f) Orthoptic graft- Anatomically similar position
g) Alloplast -Inert synthetic material (synthetic bone and implant)
h) Xenograft -From different animal
SYSTEMIC MICROBIOLOGY
 151.Staphylococcus aureus
o Mannitol fermenting, pathogenic.
o Haemolytic forms—oil paint colonies on nutrient agar.
o Selective media—Ludlum's and McConkey's media.
o Nonmotile, norisporing, grampositive cocci
o Occur in grapelike clusters
o Beta haemolysis on blood agar
o Coagulase and catalase positive
o Produces phosphatase

21. o Liquifies gelatin
o Produces golden yellow pigment
o Reduces tellurite
o Facultative anaerobic
o Coagulase positivity—marker of pathogenicity
 Catalase positive—Bacillus, E.coli, Nisseria, nonsporing anaerobes,
staphylococci.
 Most common cause of .food poisoning is Staphylococcus.
 Dick test—erythrogenic toxin is tested for susceptibility to scarlet fever.
 Schultz Charlton test—uses antitoxin for presence of erythrogenic toxin in
scarlet fever.
 Stitch abscess—is caused by Staphylococcus albus.
 Clinical manifestations of Staphylococcal infection
a.Superfical infections—Pyoderma, folliculitis, furuncle, abscess, carbuncle
b. Deep infections—Osteomyelitis, pneumonia, acute endocarditis, arthritis
 Staphylococcal toxin diseases—Scalded skin syndrome, food poisoning,
Scarlantiform syndrome, toxic shock syndrome, Desquamation
 Staphylococci are betalactamase enzyme producers—betalactamase
inhibitor should be given in addition to betalactam antibiotics.
 Lancefield classified beta haemolytic streptococci based on 'C
polysaccharides on cell wall.
 M protein is virulence factor for Streptococcus.
 Betahaemolytic streptococci—example is Streptococcus pyogenes.
Lancefield group beta haemolytic are 20 distinct groups based on
antigenicity.

22.  Alpha haemolytic—greenish discolouration—Streptococcus viridans
(Streptococcus salivarius).
 Alphahaemolysin is pathogenic in man.
 Beta haemolytic contains streptolysin (O and S); streptokinase,
hyaluronidase etc—Haemolytic group
 Streptodornase—causes depolymerisation of DNA.
 Gamma haemolytic—Streptococcus faecal is—suterococcus group
 An ASO titer higher than 160 is indicative of previous streptococcal
infection.
 Osler nodes are seen in subacute bacterial endocarditis.
 Clostridium:
o Clostridium difficile causes pseudomembranous colitis.
o Clostridium perfingens causes gas gangrene.
o Clostridium botulinum causes botulism. Botulism—flaccid paralysis.
o Clostridium tetani causes tetanus (tetanospasmin—neurotoxin;
tetanolysin—haemolysin).
 Tetanus toxin inhibits acetylcholinesterase, thus causing spasm of muscles.
 Tetanus toxoid—active immunization.
 ATS—passive immunization (Antitetanus serum) (Antitetanus globulin)
 ATG—to prevent hypersensitivity occurring in passive immunization.
 Endospores are characteristic of Bacillus and Clostridium.
 Pneumococci contain the antigen in the capsule (capsular polysaccharide).
 Nagler's reaction is for detecting lecithinase (Clostridium perfingens).
 Corynebacterium diphtheriae (KlebsLoeffler bacillus):
o Contains metachromatic granules (BabesErnst granules). Causes bull
neck and temporary paralysis of soft palate.

23. o Requires lysogenic phase conversion by beta phage for toxin
production.
 Elek's test—test for toxigenicity—detection of diphtheriae.
 Shick test—if it is positive, patient is susceptible to infection. If it is
negative patient is immune to infection.
 Tetanus, diphtheria, staphylococcus—release exotoxin.
 Traveller's diarrhoea caused by Escherichia coli.
 Diphtheria having highest mortality is laryngeal type.
 Botulinum poison acts on parasympathetic system.
 Neisseria gonorrheae:
o Doesn't follow Koch postulates.
o Oxidase positive.
 Oral gonococcal lesions most commonly affect tongue, gingivae, soft palate
in oral cavity. Ophthalmia neonaturum—is complication in newborns from
gonorrheal infected mother.
 Spore formation occurs in stationary phase.
 Satellitism is found in cultures of Haemophilus.
 Fried egg colony is found in Mycoplasma.
 Mycobacterium tuberculosis—tuberculosis of lungs is called phthisis; skin-
lupus vulgaris; lymph nodes-scrofula; bones-Pott's disease.
 Test used to differentiate Mycobacterium tuberculosis form atypical
mycobacterium—niacin test.
 Mantoux positive (prior infection clinical/sub clinical).
 Galloping consumption—TB (rapid spreading).
 In HIV infection, kwashiorkar—Mantoux test is false negative.
 Treponema pallidum—Giemsa staining.

24.  Minimum number of treponemes required for detection by dark ground
microscope is 104/mL.
 TPI (treponemal immobilization test)—most specific test for syphilis.
 Fluorescent treponemal antibody test—sensitive for syphilis.
 Wasserman test—standard nonspecific test for syphilis.
 Primary syphilis » 2-3weeks (incubation period).
 Secondary syphilis >2-3months (incubation period).
 Tertiary syphilis—few years.
 Cor bovinum appearance of heart is seenjn syphilis.
 'Dharmendra' antigen is most commonly used antigen for lepromin test.
 Lepromin test—asseses the prognosis and response to treatment.
 Leonine face—is a condition present in lepromatous leprosy.
 Fastest bactericidal drug for M. leprae is rifampicin.
 Acid fast bacteria arranged in "cigarettes in a pack" is Mycobacterium
leprae.
 Pneumococcus:
o Lanceolate/flame shaped
o Produce alpha haemolysis on blood agar
o Differ from streptococci in
o Optochin sensitivity
o Bile solubility
o Polysaccharide capsule
o Inulin fermentation
 Blue pus is associated with pseudomonal infection.
 Salmonella food poisoning is not toxin mediated.
 Salmonella typhi requires tryptophan for its growth.

25.  Grampositive anaerobes—propionibacterium, lactobacillus,
peptostreptococci
 Gramnegative anaerobes—violenella.
 Tests used for differentiation of bacteria:
o Oxidase test- Identification of Neisseria
o Coagulase- Differentiation of Staphylococci from streptococci
o Urease- Differentiation from Streptococcus mutans
o Inulin fermentation- Differentiation from streptococci and
pneumococci
o Mannitol/sorbital-Differentiation from Streptococcus mutans and
oral streptococci
VIROLOGY
 Viruses were discovered by Iwanowsky.
 Viruses are smallest infectious agents containing only one kind of nucleic
acid as their genetic material.
 Glycoprotein is component of virus particle that is responsible for
pathogenicity.
 Viruses consist of nucleic acids surrounded by one or more proteins.
 Nucleic acid present may be DNA or RNA.
 DNA viruses are:
o Adenovirus—swimming pool conjunctivitis (group B adenovirus),
gastroenteritis (group F).

26. o Poxvirus—smallpox, molluscum contagiosum.
o Papovavirus—papilloma, polyoma, vaccinia viruses.
o Parvo—erythema infectiosum (fifth disease). . Herpes—HSV I, II,
III, IV, V, VI, VII.
o Hepadna—hepatitis B.
 RNA viruses are:
o Picorna—polio, Coxsackie, echo, rhino, hepatitis A.
o Orthomyxovirus—influenza.
o Paramyxovirus—mumps, measles, respiratory syncitial virus.
o Toga virus—rubella, yellow fever.
 Herpes virus causes conjunctival infections.
 HSV 1—herpes simplex virus (primary)—causes acute herpetic gingivo
stomatitis.
 HSV 2—herpes simplex virus (secondary)—causes genital lesions.
 HSV 3—varicella zoster virus, causes chickenpox.
 HSV 4—EpsteinBarr virus causes infectious mononucleosis.
 HSV 5—Cytomegalovirus causes cytomegalic inclusion disease.
 HSV 6—Human blood lymphotropic virus.
 Differences between
o Virusoids—Nucleic acids that depends on helper viruses for package
of nucleic acids into viruslike particle
o Viroids—Naked, cyclical, mostly RN A and resticted to plants
o Prions—Abnormal cellular proteins that can spread from cell to cell
 Eclipse stage—absence of demonstrable viral particle.
 Elution—reversal of haemagglutination due to reversal of destruction of
RBC. Seen in myxovirus.

27.  Poxviruses are largest (300 nanometers), picorna viruses are smallest (foot
and mouth disease virus 20 nm).
 Viruses are obligate intracellular parasites.
 Chemical composition of virus presents proteins (structural capsid and
peplomers enzymatic RNA polymerase etc.), nucleic acid (either DNA or
RNA), liquid (cell membrane/nuclear membrane) and carbohydrate.
 Most viruses are heat labile and disrupted under alkaline conditions, pH 9 to
10 and temperature of 56°C.
 Only virus that has double stranded RNA—reovirus.
 Single stranded DNA is seen in parvovirus.
 Transcription in RNA virus is done by RNA dependant RNA polymerase
and in DNA virus by DNA dependant DNA polymerase.
 Viruses are usually cultivated on three kinds of systems—lab animals,
embryonated eggs and tissue culture.
 Viropexis—induction of virus into a susceptible cell and mechanism by
which virus particles are eugulfed by animal cell
 Antiviral disinfectants
o H202
o KMnO2
o Hypochlorites
 Hepatitis B serology:
o HBs Ag/Australian antigen- Earliest and most specific marker of
active infection
o HBc Ag/Core antigen- Seen in liver cells and not in sera of affected
o HBe Ag/e antigen -Highly infective state, adverse prognostic feature
Indicates viral load.

28. o HBsAb- Indicates past infection, with immunity to HBV
o HBcAb/AntrHBcAg -Past or present infection
o HBeAb/antiHBeAg -Resolution of active infection
o Anti HBc IgM -Best indicator of acute infection
o AntiHDVIgM -Recent infection
 Most sensitive index of hepatitis "B" is Southern blot.
 Most sensitive test for antigen detection is RIA (radium immune assay).
 NonA nonB hepatitis virus is common in India.
 HIV virus is also called as HTLV virus (human T cell lymphatic virus).
 HTLVIII is associated with causing of AIDS disease (type II and I are
associated with leukaemia).
 Monocytes serve as a major reservoir of HIV in body.
 Protozoal infections associated with HIV are Pneumocystis carinii and
toxoplasmosis.
 Most common fugal infections seen in HIV are Candida albicans and
Cryptococcus neoformans.
 Most common bacterial infections seen in AIDS are Mycobacterium
tuberculosis, Mycobacterium avium.
 CMV, HSV and adenovirus are commonly associated with AIDS.
 HIV virus is isolated from lymphocyte in peripheral smear and bone
marrow.
 Serological features of HIV are:
o Antigen detection (p24)—appears in blood after 2 weeks.
o Antibody detection—after 3 to 6 months of infection.
o Most sensitive screening test is ELISA.
o Most specific diagnostic test is WESTERN BLOT.

29.  Routes of HIV transmission are blood and its products, vertical transmission
(mother to child) and sexual contact.
 HIV attacks helper T cell mainly, thus giving rise to abnormal T4/T8 ratio.
 Measles—highly infectious in catarrhal stage.
 Route of entry of poliovirus is usually through gastrointestinal tract.
 Poliovirus in oral polio vaccine causes production of IgA.
 Rickettsia—obligatory intracellular parasites containing both DNA and
RNA.
 Rickettsial infections are usually transmitted from bites of infected vector
insects.
 Rickettsial disease with oral manifestations is rickettsial pox.
 Virus and rickettsia cause interstitial pneumonia.
 Shigella—classified based on mannitol fermentation.
 Chlamydia trachomatis causes trachoma, lymphogranuloma venereum
(LGV), inclusion conjunctivitis.
 Oral lesions of LGV are seen in tongue.
 Chlamydia psittacosis causes psittacosis and ornithosis.
 Inclusion bodies:
 Donovan bodies- Lymphogranutoma venereum (LGV)
 Owl eye inclusion -Cytomegalovirus and herpes
 Negri bodies -Rabies
 Gaurneri (intracytoplasmic) Vaccinia virus(artificial)- smallpox
 Lipschutz- Herpes
 Prowazek bodies -Trachoma
 Asteroid/Schumann- Schwanomma
 Cowdry type A (intranuclear) -Herpes

30.  Cowdry type B (intranuclear)- Poliomyelitis virus
 Reiley bodies- Hurler syndrome
 Pappenheimer bodies -Haemosiderosis
 Howell Jolly bodies- Megaloblastic anaemia
 Bollinger bodies -Fowl pox
FUNGI
 Cause disease by hypersensitivity.
 Fungal infection that mimics TB is histoplasmosis.
 Diabetic patients are commonly affected by Cryptococcus fungal infection
(palate).
 Pseudohyphae are found in Candida infection.
 Cholera associated fluid loss, acidosis and hypokalaemia.
 Gilchrist's disease called as North American blastomycoses.
 Valley fever/Sanjanqui valley fever—coccidiodomycoses.
 Lutz disease—South American blastomycoses.
 Sialedintis—caused by Staphylococcus aureus.
 Aa.commitans, Bacteroides and Capnocytophaga cause periodontitis.
 Aa.commitans inhibits production of leukotoxins.
 Capnocytophaga inhibits chemotaxis of neutrophils.
 Bacteroides require haemin for growth—release collagenase that is
responsible for peridontitis.