🧪 Quick Lab Snapshot (HIGH-YIELD) • Gram stain: Gram-positive cocci in chains • Catalase: Negative ❌ • Hemolysis: β-hemolytic (clear zone) • Group: Lancefield Group A • Bacitracin: Sensitive • PYR: Positive 🩺 Classic Clinical Associations • Pharyngitis (“strep throat”) • Scarlet fever (strawberry tongue 🍓) • Impetigo • Cellulitis • Necrotizing fasciitis • Rheumatic fever (post infection complication) • Post-strep glomerulonephritis 💡 Exam Mnemonic “A PYRate is Sensitive” 👉 Group A Strep 👉 PYR positive 👉 Bacitracin sensitive You see Gram-positive cocci in chains with beta hemolysis. What is your NEXT test? 👇 Drop your answer below! Answer + explanation later…

🧪 Quick Lab Snapshot (High-Yield) • Gram stain: Gram-positive cocci in clusters 🍇 • Catalase: Positive ✅ • Coagulase: Positive ✅ (key differentiator) • Blood agar: β-hemolysis • MSA: Grows + ferments mannitol → yellow • Reservoir: Normal skin & nares 🩺 Clinical Associations • Skin & soft tissue infections (boils, abscesses) • Pneumonia (post-influenza 👀) • Osteomyelitis • Endocarditis • Toxic shock syndrome • Food poisoning (preformed toxin) 💡 Exam Tip / Mnemonic “CATs & COAG” 👉 Staph aureus is CATalase positive and COAGulase positive 💬 What’s the first test you think of when you see Gram-positive cocci in clusters on a Gram stain?