Interrepeat fingerprinting of third-generation cephalosporin-resistant Enterobacter cloacae isolated during an outbreak in a neonatal intensive care unit.

Objective: To investigate an outbreak in neonates of Enterobacter cloacae infection resistant to third-generation cephalosporins.

Design: A retrospective study of an outbreak in the neonatal intensive care unit (NICU) and review of E cloacae isolates in pediatric wards and other intensive care units from June 1992 through March 1993.

Setting: An academic tertiary care hospital.

Patients: Six patients admitted to the NICU were colonized or infected with E cloacae resistant to third-generation cephalosporins. In the period preceding the outbreak, four E cloacae isolates were available from four patients in the pediatric surgical ward. Nine isolates from four patients in two other intensive care units (ICUs) also were collected during the outbreak. Isolates were biotyped by the API 50CH system and genotyped by polymerase chain reaction (PCR) fingerprinting.

Results: Typing by interrepeat PCR showed that 21 isolates, which were obtained from five neonates, were identical. One neonate was colonized with a different strain. Some neonates were colonized with a single type of E cloacae for a relatively long period of time. Isolates of patients who were cared for in the pediatric surgical ward and the two other intensive care units (ICUs) showed different genotypes. One patient in an ICU was colonized with an E cloacae strain genetically identical to the outbreak strain. No predominant biotype could be established.

Conclusions: E cloacae can colonize neonates for a long period of time and although colonization with E cloacae initially may arise endogenously, we were able to show further transmission by cross-contamination in a neonatal intensive care unit.