Determination of the microbiological safety of selected fresh produce of informal retailers point-of-sale

[摘要] ENGLISH ABSTRACT: The global consumption of fresh produce has increased as consumers have become more health conscious. With the rise of fresh produce consumption, fresh produce related foodborne outbreaks also increased globally. Recent outbreaks have included the E. coli O157:H7, Listeria monocytogenes and Salmonella infections caused by contaminated fresh produce in 2018, 2016 and 2015, respectively. To minimise the risk for foodborne outbreaks in fresh produce it is important to know the current microbiological safety status of fresh produce in South Africa. Limited information is available about the microbiological safety of fresh produce sold at informal markets. Fresh produce is often consumed raw and therefore the microbiological risk is higher. A group of environmental bacteria, the Extended Spectrum β-Lactamases (ESBL) producing Enterobacteriaceae, are also of concern because of their ability to counteract the effect of antibiotics and spread to the environment and fresh produce.The aim of this study was to determine the microbiological safety of fresh produce sold at the informal market in the Cape Town Metropolitan area, South Africa, by enumerating hygiene indicator systems such as coliforms, E. coli and Enterobacteriaceae. Indicator systems, however, do not give an indication of the presence of specific pathogens. The presence of produce-related pathogens such as Salmonella, Listeria monocytogenes and Shiga Toxin-producing E. coli (STEC) were also investigated. Also included in this study was the detection of Extended Spectrum β-Lactamase (ESBL) producing bacteria and their antibiotic resistance profiles.Five informal vendors were selected to represent the informal market in the Cape Town metropolitan area. Each site was visited three times and at each site, two different products were selected for sampling (five replicates of each product). The fresh produce tested in this study included lettuce, cabbage, spinach, tomatoes, green beans and green peppers.The general hygiene counts for all sites were well over the advised coliform limits according to the Department of Health. No Salmonella or Listeria monocytogenes was detected in any of the fresh produce. The presence of E. coli occurred in sporadic cases indicating evidence of poor handling practices at the informal vendors. The prevalence of ESBL producing Enterobacteriaceae was relatively low with 4% of the fresh produce sampled that tested positive for ESBL producing Enterobacteriaceae. Multiplex polymerase chain reaction (PCR) was used to confirm the presence of the most prevalent ESBL genes in an isolate namely blaTEM, blaCTX-M and blaSHV. Out of the seven phenotypically confirmed ESBL producing Enterobacteriaceae, five isolates were confirmed as containing at least one of the ESBL genes of interest. All ESBL producing Enterobacteriaceae were multidrug resistant as well, being resistant to at least Ampicillin, Cloxacillin and/or Cefoxitin, Tetracycline, Ciprofloxacin and Trimethoprim-sulfamethoxazole. Taking all the evidence into consideration, it is clear that post-harvest handling of fresh produce can be improved. In this study, the presence of ESBL producing Enterobacteriaceae on fresh produce has been confirmed in samples sold at informal markets in the Cape Town metropolitan area. It is therefore recommended that the prevalence of these organisms is further monitored in the future.

[发布机构] Stellenbosch University