Outbreak Column 22: How to manage an outbreak

This outbreak column uses the Health Protection Scotland (HPS) Outbreak Process and Algorithm to examine and reflect on a published outbreak report. The report involved an extensively drug-resistant Acinetobacter baumannii in an oncology unit. High-reliability theory is then used to reflect on how the outbreak was managed and consider how best to improve local outbreak prevention, preparedness, detection and management. The conclusion of this exercise is that if the possibility of an era of untreatable infections caused by antibiotic-resistant organisms is to be significantly postponed, Infection Prevention and Control Teams must improve their ability to get others to prevent cross-transmission in the absence of recognised risks.

Outbreak Column 16: Cognitive errors in outbreak decision making

During outbreaks, decisions must be made without all the required information. People, including infection prevention and control teams (IPCTs), who have to make decisions during uncertainty use heuristics to fill the missing data gaps. Heuristics are mental model short cuts that by-and-large enable us to make good decisions quickly. However, these heuristics contain biases and effects that at times lead to cognitive (thinking) errors. These cognitive errors are not made to deliberately misrepresent any given situation; we are subject to heuristic biases when we are trying to perform optimally. The science of decision making is large; there are over 100 different biases recognised and described. Outbreak Column 16 discusses and relates these heuristics and biases to decision making during outbreak prevention, preparedness and management. Insights as to how we might recognise and avoid them are offered.

Pseudo-outbreak of Klebsiella oxytoca spontaneous bacterial peritonitis attributed to contamination of multidose vials of culture medium supplement

OBJECTIVE

To determine the source of a cluster of Klebsiella oxytoca isolates 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 of K. oxytoca isolates 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 grew K. oxytoca was 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 the K. oxytoca isolates 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%; [Formula: see text]).

CONCLUSION

A pseudo-outbreak of K. oxytoca peritonitis 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.