Abstract:
Shiga toxin-producing Escherichia coli (STEC) isolates (N = 38) that were incriminated in
human disease from 2006 to 2013 in South Africa were characterized by serotype, virulence-associated
genes, antimicrobial resistance and pulsed-field gel electrophoresis (PFGE). The isolates belonged
to 11 O:H serotypes. STEC O26:H11 (24%) was the most frequent serotype associated with human
disease, followed by O111:H8 (16%), O157:H7 (13%) and O117:H7 (13%). The majority of isolates were
positive for key virulence-associated genes including stx1 (84%), eaeA (61%), ehxA (68.4%) and espP
(55%), but lacked stx2 (29%), katP (42%), etpD (16%), saa (16%) and subA (3%). stx2 positive isolates
carried stx2c (26%) and/or stx2d (26%) subtypes. All pathogenicity island encoded virulence marker
genes were detected in all (100%) isolates except nleA (47%), nleC (84%) and nleD (76%). Multidrug
resistance was observed in 89% of isolates. PFGE revealed 34 profiles with eight distinct clusters that
shared 80% intra-serotype similarity, regardless of the year of isolation. In conclusion, STEC isolates
that were implicated in human disease between 2006 and 2013 in South Africa were mainly non-O157
strains which possessed virulence genes and markers commonly associated with STEC strains that
have been incriminated in mild to severe human disease worldwide. Improved STEC monitoring and
surveillance programs are needed in South Africa to control and prevent STEC disease in humans.
