Step Microbiology

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  1. Choclate agar with factors V and X
    H. Influenzae
  2. Thayer-Martin media
    N. gonorrhea
  3. Bordet-Gengou agar
    B. pertussis
  4. Tellurite plate, Loffler's media
    Corynebacterium diphtheriae
  5. Lowenstein-Jensen agar
    Mycobacteria tuberculosis
  6. MacConkeys agar - pink colonies
    Lactose fermenting enterics
  7. Charcoal yeast extract buffered with cysteine
  8. Sabouraud's agar
  9. Why are aminoglycosides ineffective against Clostrridium, bacteroides, and actinomyces?
    These anaerobes and aminoglycosides require O2 to enter into bacterial cells.
  10. What are the facultative intracellular bugs?
    • Salmonella
    • Neisseria
    • Brucella
    • Mycobacterium
    • Listeria
    • Francisella
    • Legionella

    Some Nasty Bugs May Live FacultativeLy
  11. What are the encapsulated bacteria?
    • Strep pneumo
    • Klebsiella pneumo
    • Haemophilus influenzae type B
    • Neisseria meningitidis
    • Salmonella
    • group B strep

    Positive Quellung reaction
  12. Urease positive bugs
    • Proteus
    • Klebsiella
    • H. pylori
    • Ureaplasma
  13. Protein A MOA and organism
    Binds Fc region of Ig. Prevents opsonization and phagocytosis

    Staph aureus
  14. IgA protease MOA and organism
    Cleaves IgA in order to colonize respiratory mucosa

    • Strep pneumo
    • H. Influenza type B
    • Neisseria
  15. M protein MOA and organism
    • Prevent phagocytosis
    • Group A streptococcus
  16. What are the ADP ribosylating A-B toxins
    • Corynebacterium diphtheriae:
    • - inactivates elongation factor

    • Vibrio Cholerae:
    • - ADP ribosylation of G protein stimulates adenylyl cyclase: increase pumping of Cl- into gut and decrease Na+ absorption.¬†

    • E. Coli:
    • - Heat labile toxin stimulates Gs protein -> Adenylate cyclase

    • Bordetella pertussis:
    • - Increases cAMP by inhibiting Ga1
  17. Toxin of Clostridium perfringens
    • Alpha toxin
    • - a lecithinase that acts as a phospholipase to cleave cell membranes and causes gas gangrene.
  18. Toxin of shigella
    • Shiga toxin
    • - cleaves host cell rRNA (inactivates 60S ribosome)
    • - enhances cytokine release causing hemolytic uremic syndrome
  19. Streptococcus agalactiae
    • Group B streptococci, B-hemolytic
    • Bacitracin resistant
    • colonizes vagina
    • causes pneumonia, meningitis, and sepsis
    • Affects babies

    Pregnant women + get intrapartum penicillin prophylaxis
  20. Enterococci (Group D strep)
    Normal colonic flora that are penicillin G resistant and cause UTI and subacute endocarditis

    Grow in 6.5% NaCl and bile
  21. Corynebacterium diphtheria
    Diphtheria toxin exotoxin encoded by B-prophage - inhibits protein synthesis via ADP ribosylation of EF-2

    DX: via tellurite agar -> metachromatic granules
  22. 4 types of Clostridia
    1. C. tetani- tetanospasmin causes spastic paralysis

    2. C. botulinum- preformed heat-labile toxin that inhibits ACh release at NMJ

    3. C. perfringens- a toxin(lecithinase) causes myonecrosis and hemolysis

    4. C. difficile- AB toxin destroys cytoskeletal structure of enterocytes, causing pseudomembranous colitis.
  23. Nocardia
    • gram positive rod
    • weakly acid fast and aerobic
    • causes pulmonary infection in immunocompromised patients

    TX: sulfanomides
  24. What does primary infection with Mycobacterium tuberculosis lead to
    • Ghon complex (hilar nodes/ ghon focus)
    • healing by fibrosis
    • progressive lung disease
    • Miliary tuberculosis
    • Preallergic lymphatic or hematogenous dissemination -> dormant tubercle bacilli in several organs -> reactivation in adult life (CNS, Pott's, lymphadenitis, renal, GI)
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Step Microbiology
Microbiology step
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