First-line therapy for osteomyelitis often includes MRSA coverage with which agent?

First-line therapy for osteomyelitis often includes MRSA coverage with which agent?

• A. Cefazolin
• B. Ampicillin
• C. Vancomycin
• D. Aztreonam

Answer: (C)

MRSA coverage is essential in osteomyelitis because Staphylococcus aureus is a common culprit and MRSA strains are resistant to many beta-lactams. Vancomycin is the classic agent for MRSA in bone infections because it binds the D-Ala-D-Ala terminus of cell wall precursors, effectively inhibiting synthesis in MRSA, and it provides reliable bone penetration when given IV. Other options like cefazolin work well for methicillin-susceptible Staphylococcus aureus but not MRSA; ampicillin covers some Gram-positive organisms but not MRSA reliably; aztreonam targets Gram-negative bacteria and lacks Gram-positive activity. Thus vancomycin is the best initial MRSA-covering choice for osteomyelitis.

MRSA coverage is essential in osteomyelitis because Staphylococcus aureus is a common culprit and MRSA strains are resistant to many beta-lactams. Vancomycin is the classic agent for MRSA in bone infections because it binds the D-Ala-D-Ala terminus of cell wall precursors, effectively inhibiting synthesis in MRSA, and it provides reliable bone penetration when given IV. Other options like cefazolin work well for methicillin-susceptible Staphylococcus aureus but not MRSA; ampicillin covers some Gram-positive organisms but not MRSA reliably; aztreonam targets Gram-negative bacteria and lacks Gram-positive activity. Thus vancomycin is the best initial MRSA-covering choice for osteomyelitis.