Investigation of an outbreak caused by antibiotic-susceptible Klebsiella oxytoca in a neonatal intensive care unit in Norway

Aim Klebsiella spp. have been stated to be the most frequent cause of neonatal intensive care unit (NICU) outbreaks. We report an outbreak of Klebsiella oxytoca in a NICU at a tertiary care hospital in Norway between April 2016 and April 2017. This study describes the outbreak, infection control measures undertaken and the molecular methods developed. Methods The outbreak prompted detailed epidemiological and microbial investigations, where whole-genome sequencing (WGS) was particularly useful for both genotyping and development of two new K. oxytoca-specific real-time PCR assays. Routine screening of patients, as well as sampling from numerous environmental sites, was performed during the outbreak. A bundle of infection control measures was instigated to control the outbreak, among them strict cohort isolation. Results Five neonates had symptomatic infection, and 17 were found to be asymptomatically colonised. Infections varied in severity from conjunctivitis to a fatal case of pneumonia. A source of the outbreak could not be determined. Conclusion This report describes K. oxytoca as a significant pathogen in a NICU outbreak setting and highlights the importance of developing appropriate microbiological screening methods and implementing strict infection control measures to control the outbreak in a setting where the source could not be identified.