Microbiology — USMLE Step 1

نمونهٔ کارت‌ها

۱۲ کارت اول از ۱۲۵ — رو و پشت هر کارت

1. Gram-positive cocci in clusters, catalase-positive, coagulase-positive?

   Staphylococcus aureus

2. Gram-positive cocci in clusters, coagulase-negative, novobiocin-sensitive, associated with prosthetic devices?

   Staphylococcus epidermidis (biofilm)

3. Gram-positive cocci in clusters, coagulase-negative, novobiocin-resistant, UTI in young women?

   Staphylococcus saprophyticus

4. S. aureus protein A: function?

   Binds the Fc portion of IgG, blocking opsonization and phagocytosis

5. Toxin of S. aureus causing toxic shock syndrome?

   TSST-1, a superantigen

6. Toxin of S. aureus causing scalded skin syndrome?

   Exfoliative toxin (cleaves desmoglein-1)

7. Cause of rapid-onset food poisoning from preformed toxin in custard or potato salad?

   Staphylococcus aureus enterotoxin (1–6 hours)

8. Mechanism of methicillin resistance (MRSA)?

   mecA gene encoding altered PBP2a

9. Gram-positive cocci in chains, alpha-hemolytic, optochin-sensitive, bile-soluble, lancet-shaped diplococci?

   Streptococcus pneumoniae

10. S. pneumoniae virulence factor?

    Polysaccharide capsule (vaccine target); IgA protease

11. Alpha-hemolytic, optochin-resistant, viridans group, dental caries and endocarditis?

    Streptococcus mutans (caries), S. sanguinis (endocarditis)

12. Group A Streptococcus: identifying features?

    Beta-hemolytic, bacitracin-sensitive, PYR-positive, M protein