Rapid management of Serratia marcescens outbreak in neonatology unit in Singapore: Risk factors and infection control measures

We describe the investigations for control of two consecutive Serratia marcescens outbreaks in neonatology unit of Singapore General Hospital. Epidemiological investigations, environmental sampling and risk-factors analysis were performed to guide infection control measures. Active surveillance sampling of nasopharyngeal aspirate and/or stool from neonates was conducted during both outbreaks. Whole-genome-sequencing was done to determine clonal links. Retrospective case-control study was conducted for second outbreak to identify risk factors for S marcescens acquisition. In 2022, two genetically unrelated S marcescens outbreaks were managed involving five neonates in March 2022 (outbreak 1) and eight neonates in November 2022 (outbreak 2). A link to positive isolates from sinks in intensive care units and milk preparation room was identified during outbreak 1. Neonatal jaundice (aOR, 16.46; p-value= 0.023) and non-formula milk feeding (aOR, 13.88; p-value= 0.02) were identified as risk factors during second outbreak. Multiple interventions adopted were cohorting of positive cases, carriage-screening, enhanced environmental cleaning, and emphasis on alcohol-based handrubs for hand-hygiene. The two outbreaks were likely due to infection prevention practices lapses and favourable environmental conditions. Nosocomial S marcescens outbreaks in neonatology units are difficult to control and require multidisciplinary approach with strict infection prevention measures to mitigate risk factors. •Serratia marcescens acquisition is a rare occurrence in our neonatal setting.•2 consecutive clonally distinct S marcescens outbreaks occurred over 1-year period.•Nil mortality was reported during both the outbreaks.•Active surveillance & molecular analysis were crucial in both outbreaks management.•Muti-pronged approach was implemented to control both outbreaks.