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Polymicrobial Wound Triple Cover — SCE Infectious Diseases MCQ

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EasyInfection Prevention & ControlPolymicrobial Wound Triple CoverSCE Infectious Diseases

A 55-year-old man develops a wound infection after open fracture fixation. Deep tissue cultures grow a polymicrobial infection: MSSA, E. coli, and Bacteroides fragilis. What empirical antibiotic regimen covers all three organisms?

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Correct answer: B — IV Flucloxacillin (MSSA) plus IV Ceftriaxone (E

Polymicrobial wound infections require combination therapy targeting each organism class: (1) Flucloxacillin for MSSA (narrow-spectrum, targeted), (2) Ceftriaxone for E. coli (3rd-generation cephalosporin with good Gram-negative coverage), (3) Metronidazole for B. fragilis (best anaerobic coverage). Alternatively, Piperacillin/Tazobactam alone could cover all three as a single agent — but targeted therapy is preferred when organisms and susceptibilities are known. The regimen can be rationalised to narrow-spectrum agents once full susceptibility data is available.

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