Tag: #MSSA

Empiric antibiotic therapy is the initial treatment given before a specific pathogen is identified, and it’s critical for managing life-threatening infections. This guide summarizes empiric treatment strategies for most clinically important baterias and common infectious diseases. MRSA vs MSSA vs VISA vs VRSA Methicillin-resistant Staphylococcus aureus (MRSA) is a global concern in both hospital and community settings. Methicillin is is anti staphilococcal penicillin like oxacillin, nafcillin and dicloxacillin, howewer Methicillin is no longer in clinical use due to nephrotoxicity, but resistance is defined relative to it. Resistance Mechanism: MRSA acquires the mecA gene via horizontal gene transfer. This encodes penicillin-binding protein PBP2a, reducing affinity for beta-lactam antibiotics. MSSA: Oxacillin MIC ≤ 2 µg/mL MRSA: Oxacillin MIC ≥ 4 µg/mL Treatment of MSSA: Anti-staphylococcal penicillins: Oxacillin, Nafcillin, Dicloxacillin Cephalosporins: Cefazolin, Cephalexin Treatment of MRSA: First-line: Vancomycin, Daptomycin Alternatives: Linezolid, Tedizolid, Clindamycin, TMP-SMX, Doxycycline, Delafloxacin, Ceftaroline, Ceftobiprole Note: Ceftaroline is a fifth-generation cephalosporin with unique structure, effective against both MRSA (via PBP2a binding) and penicillin-resistant Streptococcus pneumoniae (via PBP2x). Vancomycin Resistance: VISA, VRSA, and VRE VISA (Vancomycin-intermediate S. aureus): Partial susceptibility to vancomycin. VRSA: Complete resistance via vanA gene from vancomycin-resistant Enterococcus (VRE) Treatment of VISA and VRSA: Daptomycin Linezolid or Tedizolid Ceftaroline Quinupristin-Dalfopristin Vancomycin-resistant Enterococcus (VRE) treatment: Linezolid, Daptomycin, Quinupristin-Dalfopristin, Tigecycline, Omadacycline, Eravacycline