MRSA (Methicillin-Resistant Staphylococcus aureus)
A strain of Staphylococcus aureus resistant to methicillin and most beta-lactam antibiotics. MRSA infections are a major hospital and community health concern. Glycopeptide antibiotics (vancomycin, telavancin, dalbavancin, oritavancin) and lipopeptides (daptomycin) are key treatments for MRSA.
Technical Context
MRSA carries the mecA gene encoding PBP2a (penicillin-binding protein 2a) — an altered transpeptidase with low affinity for beta-lactam antibiotics, conferring resistance to all penicillins, cephalosporins, and carbapenems. MRSA prevalence: approximately 20-50% of hospital S. aureus isolates in many countries (declining in some due to infection control programmes). Peptide antibiotic options for MRSA: vancomycin (glycopeptide — historical gold standard; trough-guided or AUC-guided dosing; nephrotoxicity limits prolonged use), daptomycin (lipopeptide — concentration-dependent bactericidal; for bacteraemia and right-sided endocarditis; NOT effective for pneumonia due to surfactant inactivation), telavancin (lipoglycopeptide — for complicated skin infections and hospital-acquired pneumonia), dalbavancin (lipoglycopeptide — ultra-long half-life enabling single or two-dose treatment), and oritavancin (lipoglycopeptide — single-dose treatment for skin infections). The availability of multiple peptide antibiotic classes provides crucial therapeutic options against this major pathogen.