Enterobacter cloacaecolonisation and infection in a neonatal intensive care unit: retrospective investigation of preventive measures implemented after a multiclonal outbreak

Background Enterobacter cloacaespecies is responsible for nosocomial outbreaks in vulnerable patients in neonatal intensive care units (NICU). The environment can constitute the reservoir and source of infection in NICUs. Herein we report the impact of preventive measures implemented after anEnterobacter cloacaeoutbreak inside a NICU. Methods This retrospective study was conducted in one level 3 NICU in Lyon, France, over a 6 year-period (2012-2018). After an outbreak ofEnterobacter cloacaeinfections in hospitalized neonates in 2013, several measures were implemented including intensive biocleaning and education of medical staff. Clinical and microbiological characteristics of infected patients and evolution of colonization/infection withEnterobacterspp. in this NICU were retrieved. Moreover, whole genome sequencing was performed on 6 outbreak strains. Results Enterobacterspp. was isolated in 469 patients and 30 patients developed an infection including 2 meningitis and 12 fatal cases. Preventive measures and education of medical staff were not associated with a significant decrease in patient colonisation but led to a persistent decreased use of cephalosporin in the NICU. Infection strains were genetically diverse, supporting the hypothesis of multiple hygiene defects rather than the diffusion of a single clone. Conclusions Grouped cases of infections inside one setting are not necessarily related to a single-clone outbreak and could reveal other environmental and organisational problematics. The fight against implementation and transmission ofEnterobacterspp. in NICUs remains a major challenge.