Microbiology and immunology — core pathogens, vaccines
**Gram stain / morphology:** • G+ cocci — Staph (catalase+: aureus coagulase+, epidermidis/saprophyticus-), Strep (catalase−: GAS pyogenes, GBS agalactiae, viridans, pneumoniae optochin-S). • G+ rods — Bacillus, Listeria (cold growth), Clostridium (anaerobic spore-formers), Corynebacterium. • G− cocci — Neisseria (meningitidis/gonorrhoeae). • G− rods — Enterobacterales, Pseudomonas (oxidase+, pigment), H. influenzae (chocolate X+V), Legionella (silver stain, charcoal-yeast). • Acid-fast — Mycobacterium, Nocardia, Cryptosporidium.
**Key virology:** • DNA viruses: **H**erpes, **H**epadna (HBV), **A**deno, **P**apilloma, **P**olyoma, **P**arvo, **P**ox — HHAPPPP mnemonic. • Retroviruses: HIV (RT inhibitor + integrase + protease + entry inhibitors; U=U if HIV VL undetectable).
**Immune cells (immunology):** innate — macrophage, neutrophil, NK, dendritic. Adaptive — B cells (humoral, antibody), T cells (CD4 helper, CD8 cytotoxic). MHC I on all nucleated; MHC II on APCs.
**Hypersensitivity:** • **Type I** — IgE, mast cells. Anaphylaxis, atopy. Epi IM. • **Type II** — IgG/IgM against fixed antigen. Goodpasture, AIHA. • **Type III** — immune complex. SLE, serum sickness, post-strep GN. • **Type IV** — T-cell mediated, delayed. TB PPD, contact dermatitis, GVHD.
**Vaccines (CDC Pink Book + ACIP 2024):** • **Live-attenuated** — MMR, varicella, zoster (Zostavax withdrawn 2020; Shingrix is recombinant), rotavirus, nasal flu, BCG, yellow fever, typhoid oral. Avoid in immunocompromised/pregnancy (rotavirus/MMR — discuss). • **Inactivated** — IPV, hep A, rabies, IM flu. • **Subunit/conjugate** — HBV, HPV, Tdap, Hib, PCV13/15/20/21, meningococcal. • **mRNA** — COVID-19. • **Recombinant protein** — Shingrix, RSV (Abrysvo, Arexvy).
Screen asplenia/complement deficiency → meningococcal + pneumococcal + Hib.