Empiric treatment for penicillin-allergic PD peritonitis regimen includes which antibiotic to cover Gram-positive organisms?

• A. Ceftazidime
• B. Vancomycin
• C. Aztreonam
• D. Azithromycin

Answer: (B)

When treating PD-related peritonitis empirically in someone with a penicillin allergy, it's crucial to ensure coverage of Gram-positive organisms, since staphylococci are common culprits in catheter-related infections. Vancomycin provides reliable activity against Gram-positive bacteria, including MRSA and coagulase-negative Staphylococcus, which makes it a key choice when penicillin-based beta-lactams are avoided. Its mechanism blocks cell wall synthesis by binding to the D-Ala-D-Ala terminus, a target present in Gram-positive bacteria but less effective against Gram-negatives due to their outer membrane barrier. The other options are skewed toward Gram-negative coverage or have limited Gram-positive activity, making them less suitable for ensuring Gram-positive coverage in this context. Therefore, vancomycin is the best choice for covering Gram-positive organisms in empiric therapy for penicillin-allergic PD peritonitis.