Pseudo-Outbreak ofKlebsiella oxytocaSpontaneous Bacterial Peritonitis Attributed to Contamination of Multidose Vials of Culture Medium Supplement

Abstract

Objective.To determine the source of a cluster ofKlebsiella oxytocaisolates cultured from peritoneal fluid of 3 patients with cirrhosis on a single day.Design.Outbreak investigation and before-after study.Setting.A Veterans Affairs medical center.Methods.Epidemiologic investigation, analysis of antimicrobial susceptibility testing results and molecular typing ofK. oxytocaisolates with repetitive sequence-based polymerase chain reaction (rep-PCR), review of microbiology laboratory procedures for processing peritoneal fluid cultures, and comparison of peritoneal fluid contamination rates 18 months before and after modification of laboratory procedures for culturing peritoneal fluid.Results.Each of the peritoneal fluid samples that grewK. oxytocawas inoculated into blood culture bottles by different clinicians at different hospital locations. None of the patients had clinical findings suggestive of peritonitis or elevated polymorphonuclear cell counts in peritoneal fluid (range, 3-25 cells/μL). Molecular typing with rep-PCR demonstrated that theK. oxytocaisolates were genetically related (greater than 95% similarity). Laboratory procedures included the routine addition of a culture medium supplement of yeast extract and dextrose from a multidose vial into blood culture bottles with peritoneal fluid. After discontinuing use of the culture medium supplement, there was a marked reduction in the number of peritoneal fluid cultures deemed as contaminants (14.3% vs 0.9%;P<.001).Conclusion.A pseudo-outbreak ofK. oxytocaperitonitis and high rates of contamination of peritoneal fluid were attributable to contamination of a multidose culture medium supplement. This article highlights the importance of discouraging the use of multidose vials in all clinical settings.