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Polymicrobial DFO MRSA Pseudomonas — SCE Infectious Diseases MCQ

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ModerateBone & Joint InfectionPolymicrobial DFO MRSA PseudomonasSCE Infectious Diseases

A 55-year-old man with diabetes develops a diabetic foot ulcer infection. Wound probe-to-bone test is positive. MRI confirms osteomyelitis of the calcaneum. Deep tissue culture grows MRSA (Vancomycin MIC 1 mg/L) and Pseudomonas aeruginosa. What is the most appropriate regimen?

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Correct answer: A — IV Vancomycin (for MRSA) plus IV Meropenem or Ceftazidime (for Pseudomonas)

Polymicrobial diabetic foot osteomyelitis with MRSA and Pseudomonas requires combination therapy targeting both organisms. IV Vancomycin (targeting AUC/MIC 400–600 for MRSA) plus an anti-pseudomonal agent (IV Meropenem or Ceftazidime or Piperacillin/Tazobactam) is the standard approach. The calcaneal location (hindfoot) is associated with worse outcomes than forefoot osteomyelitis and more often requires surgical intervention. The probe-to-bone test has ~90% positive predictive value for osteomyelitis in the presence of an infected ulcer.

Reference: https://www.nice.org.uk/guidance/conditions-and-diseases/infections