Recurrent outbreaks of Serratia marcescens among neonates and infants at a pediatric department: an outbreak analysis.

Purpose: Serratia marcescens is a known cause of bloodstream infections (BSIs) and outbreaks in neonates receiving intensive care. Our aim was to analyze clinical and epidemiological characteristics of two outbreaks detected in our unit to prevent and control further epidemic infections.

Methods: Two episodes of BSI outbreaks in neonates have been investigated in a 20-month period at a pediatric department of a medical university in Hungary. We collected all S. marcescens strains that were isolated in the study period, and two strains that were isolated before the outbreaks. Strains were analyzed by pulsed-field gel electrophoresis (PFGE). Clinical data were collected for the BSIs during and between the outbreaks (n = 14).

Results: Out of the 28 S. marcescens isolates investigated by PFGE, 16 were blood isolates. All isolates represented four PFGE types. Pathogenic strains that caused epidemic BSIs were related to a single PFGE type (SM009). Strains with the same pulsotype could be detected before, between, and after the outbreak periods from surveillance cultures of neonates, and a water tap in the infant care unit despite intensive infection control measures. Case fatality rate of BSIs was 29%. Rate of complications in central nervous system was high: 3/14 neonates developed meningitis.

Conclusions: Rapid spread and high mortality rate of S. marcescens infections necessitate a high suspicion when isolating this species in neonatal intensive care. Early identification of outbreaks is essential, that can be facilitated by determination of clonal relatedness using molecular methods, and with regular surveillance cultures of patients and environment.