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

Laubscher, Anika (2019-04)

Thesis (MScFoodSc)--Stellenbosch University, 2019.

Thesis

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.

AFRIKAANSE OPSOMMING: Die wêreldwye verbruik van vars produkte het toegeneem namate verbruikers meer gesondheidsbewus geword het. Met die toename in varsprodukte inname het varsprodukte verwante voedsel-uitbrake ook wêreldwyd toegeneem. Onlangse uitbrake sluit in die E. coli O157:H7, Listeria monocytogenes en Salmonella besmette produkte wat onderskeidelik in 2018, 2016 en 2015 plaas gevind het. Om die risiko van uitbrake in vars produkte te verminder, is dit belangrik om die huidige mikrobiologiese veiligheidstatus van vars produkte in Suid-Afrika te monitor. Beperkte inligting is beskikbaar oor die mikrobiologiese veiligheid van vars produkte wat verkoop word in informele markte in Suid Afrika. Varsprodukte word dikwels rou geëet en daarom is die mikrobiologiese risiko hoër. 'n Groep omgewingsbakterieë, Extended Spectrum β-Lactamase (ESBL) produserende Enterobacteriaceae, is ‘n kommer weens hul vermoë om die effek van antibiotika teen te werk wanneer ‘n individu geinfekteer word as gevolg van die verspreiding na die omgewing asook vars produkte. Die doel van hierdie studie was om die mikrobiologiese veiligheid van vars produkte wat in informele markte in die Kaapstadse metropolitaanse gebied, Suid-Afrika, verkoop word, te bepaal. Dit is gedoen deur higiëne-aanwysersisteme soos coliforme, E. coli en Enterobacteriaceae te bepaal. Higiëne-aanwysersisteme gee egter nie aanduiding van die teenwoordigheid van spesifieke patogene nie. Die teenwoordigheid van patogene, algemeen teenwoordig in varsprodukte, naamlik Salmonella, Listeria monocytogenes en Shiga Toxin-produserende E. coli (STEC) is ook bepaal. Ook ingesluit in hierdie studie was die deteksie van ESBL produserende bakterieë en hul antibiotiese weerstandsprofiele. Vyf informele verkopers is gekies om die informele mark in die Kaapstadse metropolitaanse gebied te verteenwoordig. Elke mark is drie keer besoek. By elke mark is twee verskillende produkte gekies waar vyf replikate van elke produk geneem is. Die vars produkte wat in hierdie studie getoets is, sluit in blaarslaai, kool, spinasie, tamaties, groenbone en groen soetrissies. Die algemene higiëne tellings vir meeste produkte by al die markte was oor die geadviseerde coliforme limiete volgens die Departement van Gesondheid. Geen Salmonella of Listeria monocytogenes is opgespoor in enige van die vars produkte nie. Die teenwoordigheid van E. coli het voorgekom in sporadiese gevalle, wat bewys lewer van swak hanteringspraktyke by die informele verkopers. Die voorkoms van ESBL produserende Enterobacteriaceae, was relatief laag met 4% van die varsprodukte wat positief getoets het vir ESBL produserende Enterobacteriaceae. Polimerase Kettingreaksie (PKR) is gebruik om die teenwoordigheid van die mees algemene ESBL gene in 'n isolaat te bevestig naamlik blaTEM, blaCTX-M en blaSHV. Van die sewe fenotipes bevestigde ESBL produserende Enterobacteriaceae, is vyf isolate bevestig wat ten minste een van die ESBL-gene bevat het. Alle ESBL produserende Enterobacteriaceae was ook weerstandig teen drie of meer antibiotikas insluitend Ampicillin, Cloxacillin en/ of Cefoxitin, Tetracycline, Ciprofloxacin en Trimethoprim-sulfamethoxazole. Gedurende die studie, is dit duidelik dat na-oes hantering van vars produkte verbeter kan word. In hierdie studie is die teenwoordigheid van ESBL produserende Enterobacteriaceae op vars produkte wat verkoop word by informele markte in die Kaapstadse metropolitaansegebied, Suid Afrika bevestig. Daar word dus aanbeveel dat die teenwoordigheid van hierdie organismes in die toekoms verder gemonitor moet word.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/105957
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