Vancomycin-resistant Enterococcus (VRE) outbreak in a neonatal intensive care unit and special care nursery at a tertiary-care hospital in Australia—A retrospective case-control study

OBJECTIVE: We investigated the risk factors and origins of the first known occurrence of VRE colonization in the neonatal intensive care unit (NICU) at the Canberra Hospital. DESIGN: A retrospective case-control study. SETTING: A 21-bed neonatal intensive care unit (NICU) and a 15-bed special care nursey (SCN) in a tertiary-care adult and pediatric hospital in Australia. PATIENTS: All patients admitted to the NICU and SCN over the outbreak period: January-May 2017. Of these, 14 were colonized with vancomycin-resistant Enterococcus (VRE) and 77 were noncolonized. METHODS: Demographic and clinical variables of cases and controls were compared to evaluate potential risk factors for VRE colonization. Whole-genome sequencing of the VRE isolates was used to determine the origin of the outbreak strain. RESULTS: Swift implementation of wide-ranging infection control measures brought the outbreak under control. Multivariate logistic regression revealed a strong association between early gestational age and VRE colonization (odds ratio [OR], 3.68; 95% confidence interval [CI], 1.94-7.00). Whole-genome sequencing showed the isolates to be highly clonal Enterococcus faecium ST1421 harboring a vanA gene and to be closely related to other ST1421 previously sequenced from the Canberra Hospital and the Australian Capital Territory. CONCLUSION: The colonization of NICU patients was with a highly successful clone endemic to the Canberra Hospital likely introduced into the NICU environment from other wards, with subsequent cross-contamination spreading among the neonate patients. Use of routine surveillance screening may have identified colonization at an earlier stage and have now been implemented on a 6-monthly schedule.