Objective To establish the number of outbreaks of extended spectrum beta-lactamase (ESBL) producing organisms in neonatal intensive care units (NICUs), to determine causes, mortality rates, proportions of infants colonised and infected and the interventions that terminated outbreaks.

Methods A systematic review of the literature in English, Spanish and French was undertaken with searches in four databases. The review conformed to the PRISMA guidelines, and the data extraction was modelled on the ORION criteria for studies of nosocomial infection.

Results 75 studies fulfilled the inclusion criteria. There were 1185 cases of colonisation, 860 infections and 139 deaths. The median outbreak duration was 6.2 months (IQR 2.0–7.5 months). Klebsiella pneumoniae was the most frequently implicated pathogen. Understaffing was the most frequent risk factor for outbreaks. The most commonly identified source was admission of an ESBL-colonised infant with subsequent horizontal dissemination. The main interventions described were improved infection-control procedures and screening of staff and the environment. 26 studies were included in the quantitative analysis. Random effects meta-analysis indicated high mortality rates in infants who developed infection (31%, 95% CI 20% to 43%).

Conclusion ESBL outbreaks in NICUs are associated with significant mortality and prolonged disruption. Understaffing is a major risk factor, but is infrequently addressed by interventions. Poor infection-control procedures are frequently implicated as contributing to ESBL spread. Better reporting of outbreaks may help clarify the role for routine ESBL screening in NICUs.