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.
Highlights
Shiga toxin-producing Escherichia coli (STEC) is a zoonotic foodborne and waterborne pathogen associated with enteric disease in humans characterized by abdominal cramps, mild to severe diarrhea, hemorrhagic colitis (HC) and hemolytic uremic syndrome (HUS) [1]
STEC isolates that were incriminated in human disease outbreaks in South Africa from 2006–2013 were fully serotyped, screened for virulence-associated genes and antimicrobial resistance patterns and subtyped by pulsed-field gel electrophoresis (PFGE)
STEC O157:H7 accounted for 13.1% (5/38) and non-O157 serotypes were associated with 87% (33/38) of STEC isolates that caused human disease in South Africa from 2006 to 2013
Summary
Shiga toxin-producing Escherichia coli (STEC) is a zoonotic foodborne and waterborne pathogen associated with enteric disease in humans characterized by abdominal cramps, mild to severe diarrhea, hemorrhagic colitis (HC) and hemolytic uremic syndrome (HUS) [1]. Majowicz et al [2] have estimated that STEC is responsible for 2.8 million cases per year of enteric disease in humans, globally. Humans acquire STEC through ingestion of contaminated foods of animal origin, water and raw vegetables or contact with infected animals [3,4,5]. More than 600 STEC serotypes have been recovered from animals, humans, the environment and various foods around the world [6,7,8]. Most STEC infections in humans have been ascribed to STEC strains belonging to seven major serogroups, including STEC
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