Deck · USMLE Step 1
Multisystem, Nutrition & Genetics
The microbiology organism roster and antimicrobials, nutrition and vitamin disorders, general neoplasia and pathology, and inherited metabolic and chromosomal disease.
150 cards · audited · SM-2 spaced repetition
Included with the full USMLE Step 1 program — 14 decks, 1,546 cards.
Sample cards
Which catalase-positive, coagulase-positive gram-positive cocci in clusters causes abscesses, endocarditis, food poisoning, and toxic shock syndrome?
Staphylococcus aureus. Coagulase-positive (distinguishes it from other staph); produces protein A (binds Fc of IgG), TSST-1 superantigen, exfoliatin (scalded skin), and a preformed heat-stable enterotoxin causing rapid-onset food poisoning. Treat with anti-staph penicillins (nafcillin/oxacillin) or vancomycin for MRSA.
Which coagulase-negative, novobiocin-sensitive staph forms biofilms and infects prosthetic devices and IV catheters?
Staphylococcus epidermidis. Coagulase-negative and novobiocin-sensitive; adheres via biofilm/polysaccharide capsule to prosthetic valves, joints, and catheters. A common blood-culture contaminant. Treat device infections with vancomycin (often methicillin-resistant).
Which coagulase-negative, novobiocin-resistant staph causes UTIs in sexually active young women?
Staphylococcus saprophyticus — the second most common cause of uncomplicated UTI in young women (after E. coli). Coagulase-negative and novobiocin-resistant (vs novobiocin-sensitive S. epidermidis).
Which bacitracin-sensitive, β-hemolytic group A strep causes pharyngitis, impetigo, scarlet fever, and triggers rheumatic fever and PSGN?
Streptococcus pyogenes (Group A Strep). β-hemolytic, bacitracin-sensitive, PYR-positive. Causes pharyngitis, cellulitis/erysipelas, impetigo, scarlet fever, necrotizing fasciitis, and toxic shock (via exotoxin A superantigen). Sequelae: rheumatic fever (M-protein molecular mimicry) and post-streptococcal glomerulonephritis. Treat with penicillin.
Which bacitracin-resistant, β-hemolytic, hippurate/CAMP-positive group B strep causes neonatal meningitis, pneumonia, and sepsis?
Streptococcus agalactiae (Group B Strep). β-hemolytic, bacitracin-resistant, CAMP-test positive, hydrolyzes hippurate. Colonizes the vagina → neonatal sepsis, pneumonia, and meningitis. Screen pregnant women at 35–37 weeks; give intrapartum penicillin prophylaxis.
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