Peritoneal Fluid/Abscess: Serratia marcescens – Shipped November 2011


A simulated peritoneal fluid/abscess sample obtained from a 45 year old male with postoperative, intra-abdominal abscess and pancreatitis was sent to category A laboratories.

Participants were expected to isolate and report Serratia marcescens. It was also expected the laboratories would report susceptibility results with a comment warning about the use of third generation cephalosporins for this type of microorganism.


  1. The reporting of a known drug/bug mismatch (e.g. reporting an intrinsically resistant organism as anything but resistant or without an appropriate comment) can lead to a major clinical error if the physician uses the antibiotic for treatment.
  2. Organisms known to produce inducible beta-lactamases can develop resistance during therapy. Special attention should be given to the reporting of third generation cephalosporins.

Full critique (PDF)

Posted in Clinical Bacteriology Results, critiques