Characterisation and epidemiological subtyping of Shiga toxin-producing Escherichia coli isolated from the beef production chain in Gauteng, South Africa

In South Africa, there is a shortage of epidemiologic data on Shiga toxin-producing Escherichia coli (STEC) in the beef production chain. This study was conducted to characterise STEC isolates originating from three studies conducted in a cattle feedlot, beef abattoirs and retail outlets in Gauteng province, South Africa. Polymerase chain reaction was used to detect virulence genes, the Epsilometer test to assess antimicrobial susceptibility, pulsed-field gel electrophoresis (PFGE) to investigate genetic relatedness of isolates, and conventional serotyping for phenotypic identification. Amongst the 86 STEC isolates, the eaeA gene was detected in 20 (23%), and 26 different serogroups were identified, including the clinically important O8, O174, O2, 020 and O117. The majority of the isolates (95%; 82/86) exhibited resistance to one or more antimicrobial agents, and 30 of the isolates (35%) exhibited multi-drug resistance (MDR), being resistant to at least three antimicrobial classes. The PFGE patterns showed a highly diverse but related STEC population, with 45 distinct patterns and evidence of horizontal transmission along the beef production chain. This is significant because it demonstrates continual environmental contamination and risk of contamination along the beef production chain and the food chain. To our knowledge, this is the first study that provides evidence of horizontal transmission of STEC along the beef production chain in South Africa. This epidemiological information could facilitate the development of a proactive strategy for reducing potential foodborne outbreaks and transmission of antimicrobial resistant pathogens in the food chain.