What is the recommended empiric antibiotic strategy for PD peritonitis in a penicillin-allergic patient?

• A. Cover Gram-negative organisms with a non–beta-lactam agent such as ceftazidime or aztreonam, tailored to culture.
• B. Cover Gram-positive organisms with vancomycin and cover Gram-negatives with a non–beta-lactam agent such as ceftazidime or aztreonam, tailored to culture.
• C. Amoxicillin alone.
• D. Use a topical antibiotic on the catheter site only.

Answer: (C)

Treating PD peritonitis in someone with a penicillin allergy requires broad coverage of both common Gram-positive and Gram-negative organisms from the start. The preferred approach is to use vancomycin to reliably cover Gram-positive bacteria (including Staphylococcus species, which are frequent culprits) and add a non–beta-lactam agent that covers Gram-negatives, such as aztreonam, to avoid beta-lactam exposure while ensuring peritoneal space drug levels are adequate. This two-drug combination is started promptly and then narrowed once culture results identify the exact pathogens and susceptibilities.

Amoxicillin alone would not provide adequate coverage of the typical Gram-negative pathogens seen in PD peritonitis, and a topical antibiotic at the catheter site does not treat an established peritoneal infection.