DNB CET Microbiology Syllabus

Microbiology syllabus — full chapter and topic list

Expand any chapter to see its topics and sub-topics. This is the whole examinable outline for Microbiology in DNB CET, not a summary of it.

1. 1

   General Microbiology and Immunology

   4 topics

   • Bacterial structure, growth and sterilization
   • Innate and adaptive immunity
   • Hypersensitivity reactions and immunodeficiency
   • Vaccines and immunization schedules
2. 2

   Systemic Bacteriology

   4 topics

   • Gram-positive cocci - Staphylococcus and Streptococcus
   • Enterobacteriaceae and gram-negative bacilli
   • Mycobacteria and acid-fast organisms
   • Anaerobes and spirochetes
3. 3

   Virology and Mycology

   4 topics

   • DNA and RNA viruses of clinical importance
   • Hepatitis viruses and HIV
   • Superficial and systemic mycoses
   • Opportunistic fungal infections
4. 4

   Parasitology and Applied Microbiology

   3 topics

   • Protozoa - Plasmodium, Entamoeba, Leishmania
   • Helminths - cestodes, trematodes, nematodes
   • Hospital-acquired infections and antimicrobial stewardship

Microbiology flashcards for DNB CET

24 of 60 cards from the Microbiology deck — real questions with worked answers.

1. Which structural component of the bacterial cell wall is the target of penicillin and confers shape/rigidity?

   Peptidoglycan (murein) - a polymer of N-acetylglucosamine and N-acetylmuramic acid cross-linked by peptide bridges; penicillin inhibits transpeptidase (PBP) cross-linking.

2. What are the key differences in cell wall between Gram-positive and Gram-negative bacteria?

   Gram-positive: thick peptidoglycan layer, teichoic acid, no outer membrane (stain violet). Gram-negative: thin peptidoglycan, outer membrane with LPS (endotoxin), periplasmic space (stain pink/red).

3. What is the active component of endotoxin (LPS) and which part is responsible for toxicity?

   Lipopolysaccharide of the Gram-negative outer membrane; Lipid A is the toxic moiety, causing fever, hypotension and DIC (septic shock).

4. Name the four phases of the bacterial growth curve in order.

   Lag phase, Log (exponential) phase, Stationary phase, Decline (death) phase.

5. What temperature, pressure, and time define standard autoclave sterilization?

   121 degrees C at 15 psi (15 lb/sq inch) for 15-20 minutes (moist heat / saturated steam).

6. Which biological indicator is used to test autoclave efficiency vs hot air oven?

   Autoclave: spores of Geobacillus stearothermophilus (Bacillus stearothermophilus). Hot air oven: spores of Bacillus subtilis (atrophaeus / Clostridium tetani).

7. What temperature and time are used for hot air oven (dry heat) sterilization?

   160 degrees C for 1-2 hours (dry heat); used for glassware, metal instruments, oils and powders.

8. Differentiate sterilization, disinfection, and antisepsis.

   Sterilization: complete removal/killing of ALL microbes including spores. Disinfection: killing of vegetative pathogens (not necessarily spores) on inanimate objects. Antisepsis: use of chemicals on living tissue to inhibit microbes.

9. Which cells and molecules constitute the FIRST line of innate immune defense?

   Physical/chemical barriers (skin, mucosa, lysozyme, acid pH), phagocytes (neutrophils, macrophages), NK cells, complement, and inflammatory cytokines - non-specific, no memory.

10. What is the key distinction between innate and adaptive immunity?

    Innate: rapid, non-specific, no immunological memory (germline-encoded receptors, e.g. TLRs). Adaptive: slower, antigen-specific, has memory, mediated by T and B lymphocytes (clonal selection).

11. Which immunoglobulin crosses the placenta and which is the first produced in a primary response?

    IgG crosses the placenta (passive immunity to fetus). IgM is the first/largest antibody produced in the primary immune response (pentamer).

12. Which immunoglobulin is the main antibody in mucosal secretions, and which mediates type I hypersensitivity?

    IgA (secretory, dimer) is the predominant mucosal/secretory antibody. IgE mediates type I hypersensitivity and parasite defense.

13. What are the three pathways of complement activation and the common convergence point?

    Classical (antigen-antibody), Alternative (microbial surfaces), and Lectin (MBL binding mannose) pathways; all converge at C3 activation leading to the membrane attack complex (MAC, C5b-9).

14. Which complement components are anaphylatoxins and which is the major opsonin?

    Anaphylatoxins: C3a, C4a, C5a (C5a is also a potent chemotactic). Major opsonin: C3b.

15. List the four types of hypersensitivity reactions (Coombs and Gell classification).

    Type I: immediate/anaphylactic (IgE). Type II: cytotoxic/antibody-mediated (IgG/IgM). Type III: immune complex-mediated. Type IV: delayed/cell-mediated (T cells).

16. Give a classic example of each hypersensitivity type.

    Type I: anaphylaxis/asthma/atopy. Type II: hemolytic transfusion reaction, Goodpasture. Type III: SLE, serum sickness, Arthus reaction. Type IV: tuberculin/Mantoux test, contact dermatitis.

17. Which hypersensitivity type is the only antibody-INDEPENDENT one, and which cells mediate it?

    Type IV (delayed-type); mediated by sensitized T lymphocytes (CD4 Th1 / CD8) and macrophages, not antibodies. Peaks at 48-72 hours.

18. Differentiate DiGeorge syndrome and Bruton agammaglobulinemia.

    DiGeorge: thymic aplasia -> T-cell deficiency (22q11 deletion, hypocalcemia, cardiac defects). Bruton (X-linked) agammaglobulinemia: BTK mutation -> absent B cells and all immunoglobulins.

19. Which immunodeficiency causes recurrent Neisseria infections, and which causes infections by catalase-positive organisms?

    Terminal complement deficiency (C5-C9/MAC) -> recurrent Neisseria. Chronic granulomatous disease (NADPH oxidase defect) -> catalase-positive organisms (S. aureus, Aspergillus, Serratia).

20. What is the difference between active and passive immunization?

    Active: host's own immune system produces antibodies after antigen exposure (vaccine/infection) - slow onset, long-lasting, has memory. Passive: ready-made antibodies given (immunoglobulin/antitoxin) - immediate, short-lived, no memory.

21. Name the live attenuated vaccines in routine immunization.

    BCG, OPV (oral polio), MMR (measles, mumps, rubella), varicella, yellow fever, rotavirus, intranasal influenza, oral typhoid.

22. At what ages are BCG, OPV-0, and Hepatitis B birth dose given per India's National Immunization Schedule?

    All given at birth (BCG, OPV-0, and Hepatitis B birth dose within 24 hours).

23. What is the schedule for DPT/Pentavalent primary doses and boosters in the Indian UIP?

    Pentavalent (DPT+HepB+Hib): 6, 10, 14 weeks. DPT boosters at 16-24 months and 5-6 years. TT/Td at 10 and 16 years.

24. Differentiate Staphylococcus aureus from coagulase-negative staphylococci on key tests.

    S. aureus: coagulase-positive, mannitol fermenter (golden colonies), DNase-positive. CoNS (e.g. S. epidermidis): coagulase-negative; S. saprophyticus is novobiocin-resistant (causes UTI).

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