Whole genome sequence-based characterisation of Shiga toxin-producing Escherichia coli isolated from game meat originating from several European countries

Game meat is becoming increasingly popular but may be contaminated with pathogenic bacteria such as Shiga toxin-producing Escherichia coli (STEC). STEC cause gastrointestinal illnesses including diarrhoea, haemorrhagic colitis (HC), and the haemolytic uremic syndrome (HUS). The aim of this study was to assess the occurrence of STEC in 92 meat samples from chamois (n = 2), red deer (n = 27), roe deer (n = 38), and wild boar (n = 25), from Switzerland and other European countries. After enrichment, Shiga-toxin encoding genes (stx) were detected by PCR in 78 (84%) of the samples and STEC were isolated from 23 (25%) of the same samples. Nine different serotypes and eight different sequence types (STs) were found, with O146:H28 ST738 (n = 10) and O110:H31 ST812 (n = 5) predominating. None of the STEC belonged to the so-called top-five serogroups O26, O103, O111, O145, and O157. Subtyping of stx identified stx1c (n = 9), stx2a (n = 1), stx2b (n = 19), stx2e (n = 2), and stx2g (n = 1). Additional virulence factors (VFs) comprised ehx (n = 12), iha (n = 21), sta1 (n = 1), and subAB (n = 19). None of the isolates contained the eae gene. Twenty-one STEC contained VFs associated with extra-intestinal pathogenic E. coli (ExPEC). Overall, the pathogenic potential of STEC in game meat is moderate, though the isolation of one STEC strain carrying stx2a, and of STEC/ExPEC hybrids suggests a role of game meat as a potential source of STEC infections in humans. Therefore, detailed knowledge of the safe handling and preparation of game meat is needed to prevent foodborne infections.