Tracheal Wound swab: Serratia marcescens – Shipped May 10, 2021


A simulated wound sample collected from a 55 year old surgical/ICU patient with a tracheal site wound was sent to category A laboratories.

Participants were expected to identify Serratia marcescens and report its antimicrobial susceptibility.



  1. Serratia marscecens is an important nosocomial pathogen, often acquired in the community but can spread in hospitals. Its accurate identification is important for prompt and effective treatment.
  2. Caution should be exercised in reporting antimicrobial susceptibilities for this micro-organism. The penicillin and first and second generations cephalosporins are intrinsically resistant, and evidence in the literature suggests that resistance – particularly to third-generation cephalosporins can develop while patients are on therapy. Repeat testing should be considered after several days of antimicrobial treatment.

Full critique (PDF)

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