Rapid Eradication of a Cluster ofSerratia marcescensin a Neonatal Intensive Care Unit: Use of Epidemiologic Chromosome Profiling by Pulsed-Field Gel Electrophoresis

Objective:To investigate a cluster of patients infected and colonized withSerratia marcescensin a neonatal intensive care unit (NICU).Methods:In June 2001, two neonates in the NICU had clinical infections withS. marcescensand one died. Infection control surveillance data for the NICU revealed that S.marcescenswas rarely isolated from clinical specimens. Surveillance and environmental cultures were performed and isolates were typed using pulsed-field gel electrophoresis. Staff and neonates were cohorted and a waterless, alcohol-based handwashing agent was introduced. A case-control study was performed.Results:From June 2 through August 20, 2001, 11 neonates withS. marcescensinfection and colonization were identified. The incidence ofS. marcescensinfections increased from 0.19 per 1,000 patient-days in 2000 to 0.52 per 1,000 patient-days in 2001 (P< .0001). In the first 3 weeks of the investigation, there were 2 sets of patients and sinks with indistinguishable strains; however, in subsequent weeks, all isolates were of unique strains, signifying no further transmission of the two initial predominant strains. Neonates withS. marcescenswere more likely to have a lower gestational age and birth weight. There was no association between cases and healthcare workers (HCWs).Conclusions:A cluster ofS. marcescenswas quickly terminated after the introduction of preventive measures including cohorting of infected and colonized neonates and HCWs, contact precautions, surveillance cultures, and a waterless, alcohol-based hand antiseptic. Chromosomal typing determined that strains with an indistinguishable pattern were no longer present in the unit after control measures were implemented.