Hand washing soap as a source of neonatal Serratia marcescens outbreak

To describe an outbreak of Serratia marcescens infections in a neonatal intensive care unit (NICU) and to report investigations and interventions having led to the cessation of the outbreak.

Observational study of microbiological and epidemiological investigations realised during a S. marcescens outbreak between March and October 2006.

Nine cases were observed in a 5 months period. A Serratia outbreak was therefore identified, and all the strains were compared by pulsed-field gel electrophoresis (PFGE). Data from medical notes were gathered retrospectively. Environmental samples were gathered prospectively.

Four infants were colonized and five infants were infected by S. marcescens. PFGE revealed that three different strains were present. Seven of the nine babies were infected by only one of these strains. This same strain was found in a nonantimicrobial soap bottle (NAS) that could be the source of contamination.

It is the first time that S. marcescens is found in a NAS during a neonatal nosocomial outbreak. Molecular analysis is a method of choice to compare different strains. Identification and elimination of the nosocomial source and adherence to the infection control policies are essential to succeed in the containment of a nosocomial epidemic.