Article révisé par les pairs
Résumé : We used a two-step whole genome sequencing (WGS) analysis for resolving two concurrent outbreaks in two neonatal services in Belgium, caused by exfoliative toxin A-encoding-gene-positive (eta+) methicillin-susceptible Staphylococcus aureus (MSSA) with an otherwise sporadic spa-type t209 (ST-109). Outbreak A involved 19 neonates and 1 health care worker (HCW) in a Brussels hospital from May 2011 to October 2013. After a first episode interrupted by decolonisation procedures applied over 7 months, the outbreak resumed concomitantly with the onset of outbreak B in a hospital in Asse, comprising 11 neonates and 1 HCW from mid-2012 to January 2013. Pan-genome multilocus sequence typing (MLST), defined on the basis of 42 core and accessory reference genomes, and single-nucleotide polymorphisms (SNPs) mapped on an outbreak-specific de novo assembly were utilised to compare 28 available outbreak isolates and 19 eta+/spa-type t209 isolates identified by routine or nationwide surveillance. Pan-genome MLST showed that the outbreaks were caused by independent clones not closely related to any of the surveillance isolates. Isolates from only 10 cases with overlapping stays in outbreak A, including four pairs of twins, showed no or only a single nucleotide polymorphism (SNP) variation, indicating limited sequential transmission. Detection of larger genomic variation even from the outbreak beginning pointed to sporadic seeding from a pre-existing exogenous source, which persisted throughout the whole course of outbreak A. WGS analysis can provide unique fine-tuned insights into transmission pathways of complex outbreaks even at their inception, which, with a timely use, could valuably guide efforts for early source identification.

Documents en relation

DI-fusion