Contaminated parenteral nutrition solution causing a series of neonatal nosocomial infections by Serratia marcescens

Abstract

Serratia marcescens previously was thought to be a low pathogenic bacterium but has recently being recognized as a nosocomial pathogen. In May 2007, patients with nosocomial septicemia caused by S. marcescens were identified in a neonatal intensive care unit (NICU) at a tertiary-teaching hospital. The objective of this report is to highlight the rare source of the S. marcescens outbreak. Here, we describe the investigations and outcomes of this outbreak. Case subject was defined as any neonate receiving medical care at the NICU, from one week before the index patient became symptomatic and onwards, with clinical signs and symptoms of sepsis, with or without a positive blood culture, which yielded S. marcescens. Chart reviews were conducted for case subjects. Various samples from the NICU were sent for sterility testing including medications, solutions, used and freshly prepared total parenteral nutrition (TPN) from the NICU and the pharmacy unit. The specimens were processed and positive isolates were identified as S. marcescens using standard microbiological methods. S. marcescens isolates were subjected to pulsed field gel electrophoresis for molecular typing and source identification. S. marcescens were isolated from five neonates, used TPN and freshly prepared TPN of different batches in pharmacy. None of the environmental samples and medications grew S. marcescens. Analysis of macrorestriction patterns of genomic DNA by pulsed field gel electrophoresis demonstrated indistinguishable patterns. This outbreak was related to bacterial contamination of TPN. This report points at a rare source of S. marcescens outbreak. However, targeted investigations and immediate active interventions enabled the managing team to control the outbreak in the NICU.