Whole genome sequencing improved case ascertainment in an outbreak of Shiga toxin-producing Escherichia coli O157 associated with raw drinking milk

H. BUTCHER, R. ELSON, M. A. CHATTAWAY, C. A. FEATHERSTONE, C. WILLIS, F. JORGENSEN, T. J. DALLMAN, C. JENKINS, J. McLAUCHLIN, C. R. BECK, S. HARRISON
2016 Epidemiology and Infection  
SUMMARYFive cases of STEC O157 phage type (PT) 21/28 reported consumption of raw cows' drinking milk (RDM) produced at a dairy farm in the South West of England. STEC O157 PT21/28 was isolated from faecal specimens from milking cows on the implicated farm. Whole genome sequencing (WGS) showed that human and cattle isolates were the same strain. Further analysis of WGS data confirmed that sequences of isolates from an additional four cases (who did not report consumption of RDM when first
more » ... M when first questioned) fell within the same five single nucleotide polymorphism cluster as the initial five cases epidemiologically linked to the consumption of RDM. These four additional cases identified by WGS were investigated further and were, ultimately, associated with the implicated farm. The RDM outbreak strain encodedstx2a, which is associated with increased pathogenicity and severity of symptoms. Further epidemiological analysis showed that 70% of isolates within a wider cluster containing the outbreak strain were from cases residing in, or linked to, the same geographical region of England. During this RDM outbreak, use of WGS improved case ascertainment and provided insights into the evolution of a highly pathogenic clade of STEC O157 PT21/28stx2aassociated with the South West of England.
doi:10.1017/s0950268816000509 pmid:27338677 fatcat:jey377i3uzeo7pi4auq5gxt2ua