Microbial evaluation of selected produce pre- and post-pack-house and at the formal retail point-of-sale

Kavela, Efaishe Tweuhanga Angaleni (2020-04)

Thesis (MScFoodSc)--Stellenbosch University, 2020.

Thesis

ENGLISH ABSTRACT: Fresh produce consumption is important to humans as it provides important nutrients and other compounds that promote good health. However, consumption of contaminated produce can be detrimental to human health. Outbreaks linked to fresh produce consumption have been reported globally, with Enterobacteriaceae members such as Escherichia coli and Salmonella being the most frequently implicated bacteria. Fresh produce isolates carrying the extended spectrum β-lactamase (ESBL) producing Enterobacteriaceae has been reported. These organisms can resist the action of penicillin and the broad-spectrum cephalosporins, and they are also resistant to other antimicrobials. This is such a concern because fresh produce is eaten raw and these organisms are not inactivated before consumption. To be able to control the spread of contaminations and antimicrobial resistance along the fresh produce production chain, it is essential to know the microbiological quality of fresh produce at different stages of production. The aim of this study was to determine the changes in the microbiological quality of fresh produce pre- and post-pack-house processing and at the formal point-of-sale, in order to identify potential contamination points along the supply chain. Different fresh produce types: broccoli coleslaw (broccoli stems, carrots and cabbage) and lettuce samples were collected at different processing points within a pack-house situated in Phillippi, Western Cape, South Africa. Some pack-house samples (mixed coleslaw bags and lettuce pre-packs) were also collected from retail outlets. All samples were tested for microbial indicators (Enterobacteriaceae, coliforms and E. coli), Salmonella and Shiga-toxin producing E. coli (STEC). Produce samples were also screened for ESBL-producing Enterobacteriaceae. The untreated/unprocessed samples had high microbial counts which were then reduced to significantly lower levels after peeling and washing in a chlorine (150-200 ppm) solution. An increase in microbial counts to levels significantly higher than on the treated samples was observed in shredded samples and bagged mix coleslaw samples. Mixed coleslaw bags sampled from the retailer two days after packaging also had significantly higher microbial levels than mixed coleslaw from the same batch sampled at the pack-house directly after packaging. Lettuce samples have indicated a gradual decrease on microbial levels throughout, and the lowest reduction was detected on pillow-packs samples. Throughout the study, no Salmonella or STEC were detected. Fifty isolates were identified as Enterobacteriaceae with MALDI-TOF, of which 22% were confirmed as ESBL producers according to the EUCAST disk diffusion method (2017b). All 50 Enterobacteriaceae were also subjected to genotypic confirmation, and seven of them were carrying the ESBL genes: blaCTX-M and blaTEM. Enterobacter cloacae and Klebsiella oxytoca isolates were found carrying blaCTX-M and blaTEM, and a single blaTEM was found on an E. coli isolate. All 50 Enterobacteriaceae were also tested for resistance against ampicillin, gentamicin, tetracycline, ciprofloxacin, and chloramphenicol. Five of the 50 tested isolates were found to be multidrug resistant. Fresh produce is eaten raw without thermal treatment to deactivate these organisms carrying ESBL genes. Through ingesting of this produce the ESBL genes could be transferred to the intestinal microorganisms and will confer resistance to important antimicrobials. This study investigated the microbiological quality of fresh produce sold in the Western Cape and has also identified shredding and packaging as potential contamination points. Given favourable conditions, microorganisms may grow on stored fresh produce over time.

AFRIKAANSE OPSOMMING: Die verbruik van vars produkte is vir mense belangrik aangesien dit belangrike voedingstowwe en ander verbindings bied wat goeie gesondheid bevorder. Die verbruik van gekontamineerde produkte kan egter die gesondheid van mense benadeel. Daar is wêreldwyd sprake van uitbrake wat gekoppel is aan die verbruik van vars produkte, met lede van Enterobacteriaceae soos Escherichia coli en Salmonella as die bakterieë wat die meeste geïmpliseer word. Vars produkte-isolate wat die Enterobacteriaceae bevat wat verlengde spektrum ß-laktamase (ESBL) produseer, is aangemeld. Hierdie organismes kan die werking van penisillien en die breë-spektrum kefalosporiene weerstaan, en is ook bestand teen ander antimikrobiese middels. Dit is so kommerwekkend omdat vars produkte rou geëet word en hierdie organismes nie voor verbruik geïnaktiveer word nie. Om die verspreiding van kontaminasie en antimikrobiese weerstandbiedendheid in die vars produk produksieketting te kan beheer, is dit noodsaaklik om die mikrobiologiese kwaliteit van vars produkte in verskillende produksiestadia te weet. Die doel van hierdie studie was om die veranderinge in die mikrobiologiese gehalte van die voor- en na-pakhuisverwerking van vars produkte en by die formele verkooppunt te bepaal, ten einde potensiële kontaminasiepunte rondom die produksieketting te identifiseer. Verskillende soorte vars produkte: broccoli koolslaai (broccoli-stingels, wortels en kool); en blaarslaai-monsters is by verskillende verwerkingspunte in 'n pakhuis in Phillippi, Wes-Kaap, Suid-Afrika, versamel. Sommige pakhuismonsters (gemengde koolslaai-sakkies en blaarslaai-pakkies) is ook by kleinhandelswinkels versamel. Al die monsters is getoets vir mikrobiese indikators (Enterobacteriaceae, kolivorme en E. coli), Salmonella en Shiga-toksien-produserende E. coli (STEC). Vars produk monsters is ook getoets vir ESBL-produserende Enterobacteriaceae. Die onbehandelde / onbewerkte monsters het 'n hoë mikrobiese telling wat dan na afskil en was in 'n chlooroplossing (150-200 dpm) tot aansienlik laer vlakke verminder is. 'n Toename in mikrobiese tellings tot vlakke wat beduidend hoër is as by die behandelde monsters, is waargeneem in gesnipperde monsters en verpakte gemengde koolslaai monsters. Gemengde koolslaai-sakke wat twee dae na verpakking by die kleinhandelaar gemonster is, het ook beduidend hoër mikrobiese vlakke as gemengde koolslaai uit dieselfde lot wat direk na verpakking by die pakhuis geneem is. Blaarslaai-monsters het deurgaans 'n geleidelike afname van mikrobiese vlakke aangedui, en die laagste vermindering is waargeneem by opgeblaste. Gedurende die studie is geen Salmonella of STEC opgespoor nie. Vyftig isolate is met MALDI-TOF geïdentifiseer as Enterobacteriaceae, waarvan 22% volgens die EUCAST-metode (2017b) as ESBL-produsente bevestig is. Al 50 Enterobacteriaceae is ook aan genotipiese bevestiging onderwerp, en sewe van hulle het die ESBL-geen gedra: blaCTX-M en blaTEM. Enterobacter cloacae en Klebsiella oxytoca isolate is gevind met blaCTX-M en blaTEM, en 'n enkele blaTEM is in 'n E. coli isolaat gevind. Al 50 Enterobacteriaceae is ook getoets vir weerstandbiedendheid teen ampisillien, gentamisien tetrasiklien, siprofloksasien en chlooramfenikol. Daar is gevind dat vyf van die 50 getoetste isolate bestand was teen veelvuldige middels. Vars produkte word rou geëet sonder termiese behandeling om hierdie organismes wat ESBL-gene dra te deaktiveer. Deur die inname van hierdie produkte kan die ESBL-gene na die derm-mikroörganismes oorgedra word en kan dit weerstandbiedendheid teen belangrike antimikrobiese middels oordra. Hierdie studie het die mikrobiologiese gehalte van vars produkte wat in die Wes-Kaap verkoop word, ondersoek en het ook versnippering en verpakking as moontlike besmettingspunte geïdentifiseer. Gegewe gunstige toestande, kan mikroörganismes mettertyd op gebergde vars produkte groei.

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