Notes on General Microbiology

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Locations of bacteria:
Blood/internal organs: none.
Skin: S. epidermidis.
Nose: S. aureus.
Oropharynx: Viridans streptococci, S. mutans (dental plaque).
Mouth: bacteroides, prevotella, fusobacterium, streptococcus, actinomyces.
Stomach: none.
Colon: babies: bifidobacterium; adults: bacteroides / prevotella, escherichia, bifidobacterium.
Vagina: lactobacillus, Group B streptococci (infection causes meningitis and septicemia in newborns).

Bacterial colonization:
• Adherence.
• Partial adherence.
• Avoiding immediate destruction.

Ability to survive intracellularly:
• M. tuberculosis: inhibits phagosome-lysosome fusion.
• Listeria: escapes into cytoplasm before phagosome-lysosome fusion.

Toxins:
Endotoxin: LPS.
• Lipid toxin.
• Gram- bacteria; released after cell death.
• Heat stable.
• Activates macrophages, causing release of inflammatory cytokines. Causes fever, tissue damage.
• Shock and DIC follow.

Exotoxins:
• Protein toxin.
• Gram +/-.
• Secreted.
Two components:
• A: active.
• B: binds to receptors to facilitate entrance of A.
• Eg., cytolysins - lyse cell by damaging membrane.

Toxins and their Mechanisms:
Protein inhibitors:
• C. diphtheria: Diphtheria toxin: ADP ribosyl transferase; inactivates EF-2.
• P. aeruginosa: Exotoxin A: ADP ribosyl transferase; inactivates EF-2.
• S. dysenteriae: Shiga toxin: interferes with 60S ribosomal subunit.
• EHEC: Verotoxin: interferes with 60S ribosomal subunit.
Neurotoxins:
• C. tetani: Tetanus toxin: blocks release of inhibitory transmitters glycine and GABA.
• C. botulinum: Botulism toxin: blocks release of ACh.
Endotoxin enhancers:
• S aureus: TSST-1: pyrogenic (fever): decreases liver clearance of LPS; superantigen.
• S. pyogenes: enterotoxin A: similar to TSST-1.
cAMP enhancers:
• E. coli: Heat labile toxin (LT): stimulates an adenylate cyclase by ADP ribolylation of GTP binding protein.
• Vibrio cholerae: Cholera toxin: stimulates an adenylate cyclase by ADP ribolylation of GTP binding protein.
• B. anthracis: Anthrax toxin: EF/LF/PA.
• B. pertussis: Pertussis toxin: ADP ribosylates Gi, the negative regulator of adenylate cyclase; increased cAMP.
Cytolysins:
• C. perfringens: Alpha toxin: lecithinase.
• S. aureus: Alpha toxin: forms pores.

Additional Readings:

Basic Bacteriology

1. General Microbiology
2. Growth Medias and Oxygen Requirements
3. Staphylococus
4. Streptococcus
5. Enterococcus
6. Bacillus
7. Listeria
8. Corynebacterium
9. Actinomyces
10. Nocadria
11. Mycobacterium
12. Clostridium
13. Neisseria
14. Pseudomonas
15. Legionella
16. Bordetella
17. Francisella
18. Brucella
19. Campylobacter
20. Escherichia
21. Shigella
22. Klebsiella
23. Salmonella
24. Yersinia
25. Proteus
26. Vibrio
27. Pasteurella
28. Haemophilus
29. Bacteriodes and Prevotella
30. Treponema
31. Borrelia
32. Rickettsia
33. Coxiella
34. Ehrlichia
35. Chlamydia
36. Mycoplasma
37. What is an ELEK's Test?
38. Causes of Orchitis

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Page accessed on: July 29, 2010, 11:25 am.

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