Nosocomial Neonatal Outbreak of Serratia marcescens – Analysis of Pathogens by Pulsed Field Gel Electrophoresis and Polymerase Chain Reaction

Abstract.

Background: We investigated an outbreak of Serratia marcescens in the neonatal intensive care unit (NICU) and the pediatric intensive care unit (ICU) of the University Children's Hospital Leipzig, Germany.

Patients and Methods: From September to November 1998 15 patients were infected or colonized by S. marcescens. During the outbreak swabs from eye, blood, throat and nose were taken from every patient hospitalized in the ICUs.

Results: In 15 cases (14 from the NICU and one from the pediatric ICU) the cultures yielded S. marcescens. All strains were investigated by pulsed field gel electrophoresis (PFGE) as well as by polymerase chain reaction (PCR) fingerprinting. Both molecular typing methods revealed corresponding fingerprint patterns in all of the 15 isolates. Typing results of the outbreak-related isolates demonstrated that two epidemic strains of distinct genotypes were associated with cross-infections of a group of five and a group of ten patients, respectively. The three invasive and seven of the colonizing isolates were related genotypically.

Conclusion: This survey shows that PCR and PFGE are comparable in respect to the discrimination and reproducibility for epidemiological studies of S. marcescens strains in nosocomial outbreaks. Genotypic fingerprinting of bacterial isolates is useful and important to limit nosocomial infections. Fingerprinting sources of nosocomial infections can be traced both by PFGE and PCR. All patients infected recovered completely and the nosocomial outbreak could be stopped rapidly.