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Flashcards in Micro Deck (127)
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31

Vibrio cholerae
- Cholera toxin

Permanently activates Gs --> overactivates adenylate cyclase --> increased cAMP --> increased Cl- secretion in gut and H2O efflux
- Voluminous rice-water diarrhea

32

Bordatella pertussis
- Pertussis toxin

Disables Gi --> overactivates adenylate cyclase --> increases cAMP --> impairs phagocytosis --> permits survival of microbe
- Whooping cough

33

Clostridium tetani
- Tetanospasmin

Protease that cleaves SNARE --> inhibits vesicular fusion --> no NT release
- Spastic paralysis, risus sardonicus, "lockjaw"
- Prevents release of inhibitory (GABA and glycine) NT from Renshaw cells in spinal cord

34

Clostridium botulinum
- Botulinum toxin

Protease that cleaves SNARE --> inhibits vesicular fusion --> no NT release
- Flaccid paralysis, floppy baby
- Prevents release of stimulatory (ACh) at NMJ

35

Clostridium perfringens
- Alpha toxin

Phospholipase (lecithinase) --> degrades tissue and cell membranes
- Myonecrosis (gas gangrene)
- Hemolysis ("double zone" of hemolysis on blood agar)

36

Streptococcus pyogenes
- Streptolysin O
- Exotoxin A

Streptolysin O: degrades cell membrane --> Lyses RBC --> contributes to beta-hemolysis
- Host Ab against toxin (ASO) used to dx rheumatic fever
Exotoxin A: binds to MHC II and TCR outside of Ag binding site --> overwhelming release of IL-1, IL-2, IFN-gamma, TNF-alpha --> toxic shock syndrome

37

Staph aureus
- Toxic shock syndrome toxin (TSST-1)
- Exfoliative toxin
- Enterotoxin

- TSST-1: binds to MHC II and TCR outside of Ag binding site --> overwhelming release of IL-1, IL-2, IFN-gamma, TNF-alpha --> toxic shock syndrome
- Exfoliative toxin: scalded skin syndrome
- Enterotoxin: food poisoning

38

Endotoxin

- Macrophage activation --> IL-1/6 (fever), TNF-alpha (fever and hypotension), NO (hypotension)
- Complement activation --> C3a (HA release --> hypotension, edema), C5a (neutrophil chemotaxis)
- Tissue factor activation --> coagulation cascade --> DIC

39

Catalase positive

Staph

40

Coagulase positive

Staph aureus

41

Novobiocin resistant

Staph saprophyticus

42

Novobiocin Sensitive

Staph epidermidis

43

Catalase negative

Strep

44

Alpha hemolytic
- Partial reduction --> greenish/brown w/o clearing around growth

Strep viridians, Strep pneumo

45

Optochin resistant

Strep viridans

46

Optochin sensitive

Strep pneumo

47

Beta hemolytic
- Complete lysis of RBCs --> clear area surrounding colony on blood agar

Strep agalactiae (Group B), Strep pyogenes (Group A), Staph aureus

48

Bacitracin resitatnt

Group B strep

49

Bacitracin sensititve

Strep pyogenes (Group A)

50

Staph aureus

- Protein A
- TSST-1 (superantigen), exfoliative toxin, enterotoxin

51

Most common cause of septic arthritis in adults

Staph aureus

52

Most common cause of osteomyelitis

Staph aureus

53

R sided (tricuspid) endocarditis in IV drug user

Staph aureus

54

Secondary pneumonia after influenza infection

Staph aureus

55

Staph epidermidis

Normal flora of skin
Prosthetic devices and IV catheters
BIOFILMS

56

Staph saprophyticus

Uncomplicated UTI in young sexually active women (2nd to E. coli)

57

Strep pneumo

Lancet-shaped diplococci
Encapsulated
IgA protease
No virulence without capsule

58

Most common cause of meningitis

Strep pneumo

59

Most common cause of otitis media in children

Strep pneumo

60

Most common cause of pneumonia

Strep pneumo
- Rusty sputum