Many outbreaks due to Serratia marcescens among neonates have been described in the literature but little is known about the role of whole genome sequencing in outbreak analysis and management. Zingg, et al. (2017) report that between February and March 2013, two neonates and two infants previously hospitalized in the neonatal unit of a tertiary care center in Switzerland, were found to be colonized with S. marcescens. An investigation was launched with extensive environmental sampling and neonatal screening in four consecutive point prevalence surveys between April and May 2013. All identified isolates were first investigated by fingerprinting and later by whole genome sequencing. Audits of best practices were performed and a hand hygiene promotion program was implemented.
Twenty neonates were colonized with S. marcescens. No invasive infection due to S. marcescens occurred. All 231 environmental samples were negative. Hand hygiene compliance improved from 51 percent in April 2013 to 79 percent in May 2013 and remained high thereafter. No S. marcescens was identified in point prevalence surveys in June and October 2013. All strains were identical in the fingerprinting analysis and closely related according to whole genome sequencing.
The researchers concluded that improving best practices and particularly hand hygiene proved effective in terminating the outbreak. Whole genome sequencing is a helpful tool for genotyping because it allows both sufficient discrimination of strains and comparison to other outbreaks through the use of an emerging international database.