M.Sc. (Environmental Management) / Please refer to full text to view abstract

Thesis (MSc Food Sc)--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: The genus Cronobacter (Enterobacter sakazakii) contains opportunistic pathogens that can cause a severe form of neonatal meningitis, necrotising enterocolitis and septicaemia. Cronobacter infections have been reported in all age groups, however, immunocompromised infants are more susceptible to these infections. Furthermore, Cronobacter strains have been reported to show differences in sensitivity to antibiotics and virulence. These differences led to the reclassification of Cronobacter and currently the genus contains five distinct species, namely Cronobacter sakazakii, Cronobacter malonaticus, Cronobacter turicensis, Cronobacter dublinensis and Cronobacter muytjensii. As this reclassification was only accepted recently, there are not many typing methods optimised for differentiation between the five Cronobacter species. Typing of Cronobacter strains are important as the species may be diverse regarding their virulence. Cronobacter strains have been isolated from infant formula milk (IFM), the environment of an IFM processing facility and fresh produce in South Africa. However, little is known about the phylogeny and prevalence of these strains. The aim of this study was to classify 24 South African Cronobacter strains (previously identified as E. sakazakii) and to evaluate the phylogeny of the isolates based on the 16S ribosomal RNA (rRNA) and rpoA genes. All 24 South African strains were identified as Cr. sakazakii despite a wide variety of isolation sources. Other studies have also found that irrespective of the isolation source, the majority of Cronobacter strains are identified as Cr. sakazakii. The South African strains were found to be phylogenetically closely related. However, two distinct clusters separated at a 93 % confidence level were observed in the Cr. sakazakii group based on the 16S rRNA gene analysis. Strains of Cr. sakazakii, Cr. dublinensis, Cr. turicensis and Cr. muytjensii were differentiated from each other with sequence data of the 16S rRNA and rpoA genes, but it was not possible to differentiate between Cr. sakazakii and Cr. malonaticus. The phylogram based on the rpoA gene sequences did separate Cr. malonaticus and Cr. sakazakii strains, however, the clusters were separated with a low bootstrap value of 70 %. Phylogenetic analysis based on the rpoA and 16S rRNA genes were, therefore, not sufficient to distinguish between all the Cronobacter species. The sequence data of these two genes can be used to differentiate between the Cronobacter strains when used in combination with malonate utilisation analysis. A PCR-RFLP method was subsequently developed to facilitate the simultaneous differentiation between all five Cronobacter species. The PCR-RFLP assay was based on the amplification of the rpoB gene followed by the combined digestion with restriction endonucleases Csp6I and HinP1I. Unique profiles for each of the five Cronobacter species were obtained and it was also possible to differentiate between Enterobacteriaceae and Cronobacter strains. Furthermore, two strains which were identified as Cr. sakazakii with sequencing based on the 16S rRNA and rpoA genes had PCR-RFLP profiles identical to that of Cr. malonaticus. Sequencing based on the rpoB gene and additional biochemical analysis with malonate broth confirmed the identities of these two strains as Cr. malonaticus. This PCR-RFLP assay is, therefore, an accurate typing method that ensures rapid differentiation between the five species of Cronobacter. / AFRIKAANSE OPSOMMING: Die Cronobacter genus (Enterobacter sakazakii) bevat opportunistiese patogene wat 'n ernstige vorm van neonatale meningitis, enterokolitis en septisemie kan veroorsaak. Cronobacter infeksies is al in alle ouderdomsgroepe aangemeld, maar immuungekompromitteerde babas is die meeste vatbaar vir hierdie infeksies. Verder toon Cronobacter spesies verskille in virulensie en sensitiwiteit vir antibiotika. Hierdie verskille het gelei tot die herklassifikasie van Cronobacter en tans bestaan die genus uit vyf afsonderlike spesies, naamlik Cronobacter sakazakii, Cronobacter malonaticus, Cronobacter turicensis, Cronobacter dublinensis en Cronobacter muytjensii. Aangesien hierdie herklassifikasie slegs onlangs aanvaar is, is daar nie baie metodes wat geskik is vir onderskeiding tussen die vyf Cronobacter spesies nie. Onderskeiding tussen Cronobacter spesies is belangrik omdat die spesies verskillend kan wees met betrekking tot hulle virulensie. Cronobacter is geisoleer uit baba formule melk (BFM), die omgewing van 'n BFM fabriek en vars produkte in Suid-Afrika. Daar is egter nie baie bekend oor die filogenie en voorkoms van hierdie isolate nie. Die doel van hierdie studie was om 24 Suid-Afrikaanse Cronobacter stamme (voorheen geïdentifiseer as E. sakazakii) te klassifiseer en die filogenie van die isolate te evalueer gebaseer op die 16S ribosomale RNS (rRNS) en rpoA gene. Al 24 Suid-Afrikaanse stamme is geïdentifiseer as Cr. sakazakii ten spyte van 'n wye verskeidenheid isolasie bronne. Ander studies het ook gevind dat, ongeag die isolasie bron, die meerderheid van Cronobacter stamme as Cr. sakazakii geïdentifiseer word. In hierdie studie is gevind dat die Suid-Afrikaanse stamme filogeneties nou verwant is. Op grond van die 16S rRNA geen analise is die Cr. sakazakii stamme egter in twee afsonderlike groepe gedeel met 'n 93% vertrouens vlak. Dit was moontlik om stamme van Cr. sakazakii, Cr. dublinensis, Cr. turicensis en Cr. muytjensii van mekaar te onderskei met die DNS volgorde data van die 16S rRNA en rpoA gene, maar geen onderskeid tussen Cr. sakazakii en Cr. malonaticus stamme was moontlik nie. Die filogram gebaseer op die rpoA DNS volgorde data het aparte takke vir Cr. malonaticus en Cr. sakazakii stamme getoon, maar die twee takke is met ‘n lae vertrouens waarde van slegs 70 % geskei. Filogenetiese analise gebaseer op die rpoA en 16S rRNA gene is dus nie voldoende om te onderskei tussen al die Cronobacter spesies nie. Die DNS volgorde data van hierdie twee gene sou egter gebruik kon word om te onderskei tussen die Cronobacter spesies wanneer dit gebruik word in kombinasie met malonaatbenutting-analises. 'n Polimerase ketting reaksie (PKR) beperkings fragment lengte polimorfisme (BFLP) metode is ontwikkel om die gelyktydige onderskeiding tussen al vyf Cronobacter spesies te fasiliteer. Die PKR-BFLP metode is gebaseer op die vermeerdering van die rpoB geen gevolg deur die gesamentlike vertering met die beperkingsensieme, Csp6I en HinP1I. Unieke profiele vir elk van die vyf Cronobacter spesies is verkry en dit was ook moontlik om tussen Enterobacteriaceae en Cronobacter spesies te onderskei. Verder het twee stamme wat as Cr. sakazakii geïdentifiseer is met DNS volgordebepaling van die 16S rRNA en rpoA gene, PKR-BFLP profiele identies aan dié van Cr. malonaticus getoon. DNS volgordebepaling van die rpoB geen en ‘n addisionele biochemiese toets met malonaat sop het die identiteit van hierdie twee stamme as Cr. malonaticus bevestig. Hierdie PKR-BFLP is dus 'n akkurate metode wat vinnige onderskeid tussen die vyf spesies van Cronobacter kan verseker.

Thesis (MSc Food Sc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: The consumption of game meat and its by-products is increasing locally and internationally. The increase in consumption requires research that is focused on the microbiological quality of game meat. The harvesting and slaughter process of springbok carcasses revealed the presence of bacterial contamination. Swab samples taken after skinning portrayed a presence of Escherichia coli (E. coli) and Enterobacteriaceae. Springbok carcasses swabbed after chilling indicated aerobic bacteria, Clostridium spp. and lactic acid bacteria. In contrast, swab samples taken at the evisceration’s incision area tend to be lower in counts when compared to swab samples taken after skinning and after chilling. Bacterial contamination was linked to poor hygienic practices during the harvesting and slaughter process. Results showed a need for the investigation of the slaughter process. To evaluate the slaughter process’s impact on the microbial quality of game carcasses, black wildebeest (Connochaetes gnou) carcasses were sampled throughout the slaughter process. Before skinning, aerobic bacteria, Enterobacteriaceae, and E. coli were enumerated from hide samples, counts ranged from 0.92 to 7.84 log cfu/g. after skinning, bacterial counts ranged from 0.93 to 6.12 log cfu/g and further decreased after chilling. Clostridium spp. counts increased after skinning, however, statistical analysis detected no significant differences between counts. Salmonella spp. was not detected. The results indicate that bacterial contamination does occur during the slaughter process. Hygienic status during the production of game meat products was also determined. Bacterial counts from raw game meat ranged from 2.37 to 5.37 log cfu/g. Counts as high as 6.16 log cfu/g were enumerated from retail products. Aerobic plate counts (APC) from ≤ 2.62 log cfu/cm2 to ≤ 6.3log cfu/cm2 were enumerated from surfaces, hands and equipment during production. Results highlighted the inefficiency of cleaning procedures and revealed that contaminated meat can allow for bacterial contamination. To determine if muscle pH influences colour stability and microbial spoilage of game meat, normal (n=6) and dark, firm and dry (DFD) (n=6) black wildebeest Longissimus thoracis et lumborum (LTL) muscles were studied. pH affected colour, as initial (day 0) L*,a*,b*,C* and Hab values from Normal pH samples were significantly higher than values reported for DFD samples. Initial APC and Enterobacteriaceae counts from samples with Normal pH were not significantly different from counts reported for DFD samples. Initial contamination was linked to the harvesting and slaughter process. Further refrigeration (5±1ºC) for 12 days in an aerobic environment and analyses of samples every third day revealed that pH did not affect lightness and brownness as L* and b* values for DFD samples did not significantly differ overtime, the same trend was seen for samples with Normal pH. Normal pH samples showed a significant increase in a* and C* values until day 12, whilst Hab values decreased until the 12th day. The same trend was seen for a* and C* values for DFD samples until the 9th day as on the 12th day values increased. Similarly, Hab values for DFD samples decreased until the 9th day, then increased on the 12th day. Using the microbial spoilage limit of 6 log cfu/g, it was seen that DFD meat reached this limit earlier than samples with Normal pH. Overall, the study provides baseline information on the microbiological quality of game meat harvested in South Africa and slaughtered at a South African abattoir. / AFRIKAANSE OPSOMMING: Die plaaslike en internasionale verbruik van wildsvleis en wildsvleisprodukte is aan’t toeneem. Hierdie toename in verbuik vereis navorsing wat gefokus is op die mikrobiese kwaliteit van wildsvleis. Die oes-en slagproses van springbok karkasse het die teenwoordigheid van bakteriese kontaminasie aan die lig gebring. Monsters geneem met ʼn depper na afslag van karkasse het ʼn teenwoordigheid van Escherichia coli (E. coli) getoon. Springbok karkasse wat getoets is na verkoeling het hoë vlakke van die aërobiese bakterium Clostridium spp. en van melksuurbakterieë getoon. In teenstelling hiermee is getalle laer rondom die ontweidings insnyding. Bakteriese kontaminasie was gekoppel aan swak higiëne gedurende die oes- en slagproses. Hierdie resultate het ʼn ondersoek van die slagproses aangemoedig. Om die impak van die slagproses op die mikrobiese kwaliteit van wildskarkasse te evalueer, is monsters regdeur geneem van swartwildebees (Connochaetes gnou). Getalle van aërobiese bakterieë, Enterobacteriaceae, en E. coli was bepaal op vel monsters voor afslag; getalle het gewissel tussen 0.92 en 7.84 log cve/g. Getalle van bakterieë na afslag het gewissel tussen 0.93 en 6.12 log cfu/g, en het verder afgeneem na verkoeling. Clostridum spp. het toegeneem na afslag, maar statistiese analises het geen beduidende verskille getoon nie. Monsters het negatief getoets vir Salmonella spp. Die resultate toon aan dat bakteriese kontaminasie wel plaasvind gedurende die slagproses. Die higiëniese status gedurende die produksie van wildsvleis is ook vasgestel. Bakteriegetalle van rou wildsvleis het gewissel tussen 2.37 log cve/g en 5.37 log cve/g. Getalle van handelsprodukte het getalle getoon van soveel as 6.16 log cve/g. Aërobiese plaat telling tussen ≤2.62 cve/cm2 en ≤ 6.3log cve/cm2 is vasgestel vanaf oppervlakte, hande en toerusting gedurende produksie. Resultate beklemtoon die ondoeltreffendheid van skoonmaakprosedures en wys dat aangetaste vleis bakteriese kontaminasie kan toelaat. Om te bepaal of die kleurstabiliteit en mikrobiese bederf van wildsvleis geaffekteer word deur spiere se pH, is normale (n=6) en donker, ferm, en droë (DFD) (n=6) Longissimus thoracis et lumborum (LTL) spiere van die swartwildebees bestudeer. Kleur was geaffekteer deur vleis pH, siende dat die aanvanklike waardes (dag 0) vir L*, a*, b*, C* en Hab aansienlik hoër was vir monsters met normale pH as DFD monsters. Aanvanklike getalle van aërobiese plaat telling en Enterobacteriaceae telling van monsters met Normale pH het nie beduidend verskil van DFD monsters nie. Aanvanklike besmetting was gekoppel aan die oes- en slagproses. Verdere verkoeling (5±1ºC) vir 12 dae in ʼn aërobiese omgewing en analise van monsters wys dat pH nie ligtheid en bruinheid affekteer nie; waardes vir L* en b* vir DFD monsters het nie beduidend verskil oor tyd nie. Dieselfde geld vir monsters met Normale pH. Monsters met Normale pH het ʼn beduidende toename in a* en C* getoon tot en met dag 12, terwyl waardes vir Hab afgeneem het tot en met dag 12. Dieselfde patroon is waargeneem by waardes vir a* en C* vir DFD monsters tot en met dag 9, terwyl dit toegeneem het op die 12de dag. Soortgelyk het Hab waardes vir DFD monsters afgeneem tot n met dag 9, en toegeneem op die 12de dag. Dit is ook gevind dat DFD vleis die limiet vir mikrobiese bederf (6 log cve/g) vroeër bereik as monsters met Normale pH. Die studie voorsien basis inligting oor die mikrobiese kwaliteit van wildsvleis wat geoes is in Suid Afrika, en geslag is by Suid Afrikaanse slagpale.

Text in English / Fungal species and their mycotoxins are the most predorminant contaminants of dried agricultural products in sub-Saharan Africa (SSA) and the main species of fungi that can synthesize mycotoxins are Aspergillus, Fusarium and Penicillium. In Africa, aflatoxin is labelled as a great threat to human and animal health due to its high contamination levels reported of aflatoxins in foods. The aim of this study was to survey fungi and aflatoxin contamination of small-scale processed foodstuffs sold at informal retail outlets in the Johannesburg metropolis, South Africa. A total of 270 food samples (10 starch and legume based foods, 11 meat and fish based foods, 22 spices and local condiments, 14 dried fruits and vegetables) were collected from retailers; and analysed four (4) times in different seasons of spring, summer, autumn and winter. Out of the 270 samples analysed, only 27.8% were contaminated with fungal. Of all the six categories of foods analysed, roots and tubers (60.0%), nuts and seeds (40.0%), dried vegetables (37.1%), and the Meat and Insect foods (33.3%) respectively, had the most contaminated samples with fungal respectively. The least contaminated food groups were the fish foods (10.0%) and spices and local condiments (16.7%) respectively. Twenty percent of the 270 dried food analysed were contaminated by Aspergillus species out of which 61.1% of the contaminated samples had fungal counts above 103 cfu/g. Aspergillus niger was the most predominant Aspergillus species identified in all the categories of food samples analysed. Fruits and vegetables (24.4%) and the nuts and seeds (20.0%) food groups had the highest number of samples contaminated with aflatoxin. Peanut flour and Cardamom had the most incidence of aflatoxin. AFB1, AFB2 & AFG1 were the most prominent aflatoxin types recovered from the food samples. Almost all the food samples in which aflatoxin were identified had aflatoxin values above 10μg/ml. / Life and Consumer Sciences / M.Sc. (Life Science)

Phthalate esters (PEs) belong to a class of organic compounds used as plasticisers in plastic materials such as polyvinyl chloride (PVC), polypropylene (PP), polyethylene terephthalate (PET) and so on, including those used in the food packaging industry. Phthalate plasticisers are not chemically bound to plastic materials and hence, migrate into items such as foodstuffs they house. The study aimed at investigating the prevalence of selected phthalate esters from plastic wrappers into food as well as the presence of food and/or pathogenic microorganisms. Plastic-wrapped cheese, vienna sausages and polony samples purchased from commercial stores in the four regions of Pretoria (Tswane), South Africa, were analysed for the presence of plasticisers; di-2-ethylhexyl adipate (DEHA), di-n-butyl phthalate (DnBP), benzyl-butyl phthalate (BBP), di-butyl phthalate (DBP) and dimethyl phthalate (DMP). Soxhlet extraction using hexane with florisil column cleanup was carried out. Analysis of PEs was by Gas Chromatography-Flame Ionization Detection (GC-FID). Microbiological investigations were performed using standard methods. The concentrations of PEs detected in food samples ranged from below detection limit (bdl) to 4.7003 μg/kg. However, DBP, DMP and BBP were predominantly present with more PEs detected in cheese compared to polony and vienna. In polony samples, DBP levels ranged from 0.0412 to 0.611μg/kg, in cheese, ranged from 0.049 to 0.256 μg/kg and in vienna DBP ranged from 0.074 to 0.209 μg/kg. The phthalate DMP ranged from 0.072 to 4.700 μg/kg in cheese, 0.056 to 0.241 μg/kg in polony and 0.092 to 0.816 μg/kg in vienna. The DEHA detected in cheese and polony was 0.120 μg/kg and 0.075 μg/kg respectively and no DEHA was detected in vienna sausages. For microbiological analysis, the total microbial activity (TMA) ranged from 6.8 x 104 to 1.03 x 108 cfu/g; coliforms ranged from no growth to 2.62 x 106 cfu/g; yeast ranged from no growth to 1.49 x 107 cfu/g; and mould ranged from no growth to 9.2 x 104 cfu/g. The results revealed that microbial activity was high in each sample type but revealed the absence of pathogens. Results revealed incidences of PEs in foods wrapped or packaged in plastics, which gave cause for concern and showed the need for proper monitoring and inspection of the levels of organo-microbial entities in the South African food wrapped in plastic wrappers. / Environmental Sciences / M.Sc. (Environmental Science)

Thesis (MSc Food Sc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The agricultural sector of South Africa is currently facing a serious water crisis. The decreased availability of water as a result of climate change and the constantly growing population has left many farmers increasingly dependant on surface water as primary source of irrigation. Urbanisation along with out-dated and insufficient wastewater treatment works have all contributed to polluting large volumes of these resources. Consequently, many farmers have been forced to use irrigation water, not only of poor quality, but often water which has been polluted with untreated sewage. As a result, this project aimed at investigating the link between the quality of irrigation water and the impact on the safety of fresh produce. A base-line of the microbial load at three sites along the Plankenburg and Eerste Rivers was established using standard microbial methods for the detection of indicator organisms such as total and faecal coliforms, Escherichia coli and Enterococci as well as potential pathogens that included Salmonella, Listeria, Staphylococcus, endosporeformers and aerobic colony counts. Chemical parameters such as pH, alkalinity, conductivity and chemical oxygen demand (COD) were also monitored, but were not correlated to microbial pollution levels in the rivers. High faecal coliform and E. coli concentrations, ranging from 310 to 7 x 106 cfu.100 mL-1 and 230 to 7 x 106 cfu.100 mL-1, respectively, were detected. The recommended irrigation water guidelines of ≤1 000 (WHO, 1989) and ≤4 000 cfu.100 mL-1 (DWAF, 2008) for faecal coliforms and E. coli were exceeded, indicating faecal pollution and thus a high health risk. This health risk was confirmed when potential pathogens such as Aerococcus viridans, Klebsiella, Listeria monocytogenes and Salmonella typhimurium were detected at all three sites. The carryover of organisms from rivers to produce (green beans and grapes) was investigated by comparing the microbial population of the Plankenburg and Eerste Rivers to the population recovered from irrigation water and the surface of fresh produce. Faecal coliforms, E. coli, Aerococcus viridans, Enterobacter aerogenes, Klebsiella, L. innocua, L. grayi, L. monocytogenes and Staphylococcus aureus were detected in all three sample types, indicating a similarity between the microbial populations found in the river, the irrigation water and produce. Thus, the transfer of potential pathogens from the rivers to produce is a strong possibility. The build-up of organisms on the surface of green beans as a result of multiple irrigations was also confirmed by an increase in faecal coliform concentrations from initial concentrations of none detected to 44 000 cfu.100 mL-1 over a 10 day irrigation period. Finally, microbial source-tracking techniques including multi-antibiotic resistance (MAR) profiling, and the API 20E classification system were used to determine genotypic and phenotypic characteristics of 92 faecal isolates (from irrigation water and produce) and 13 reference strains. Numerical classification systems was used to classify the 105 faecal isolates according to the degree of similarity between the genotypic and phenotypic characteristics of the 105 isolates. A high degree of similarity indicates a high probability that isolates originate from the same strain and therefore from the same source, thereby confirming the transfer of organisms Faecal isolates (93 and 98%, respectively) were found to be resistant to Vancomycin at both the 5 and 30 μg concentrations. The majority of isolates presented some resistance to Erythromycin (15 μg) and Ampicillin (25 μg), with 82% of isolates presenting an inhibition zone ≤4 mm. Isolates were sensitive towards Ciprofloxacin (1 and 5 μg), Ofloxacin (15 μg), Ceftriaxone (30 μg) and Cefotaxime (5 μg), which were able to inhibit the growth of 79.8, 93.3, 79.8, 88.5 and 71.2% of the isolates, respectively. The 13 medical reference strains all presented different genotypic and phenotypic characteristics and thereby indicated a high degree of variability between isolates from the same species. Finally, 35% of the isolates could be grouped together based on similar genotypic and phenotypic characteristics, therefore, more than a third of the faecal isolates obtained from the surface of the fresh produce was as a result of faecal contaminants in the irrigation water. It could therefore be concluded that a health risk is associated with the water from the Plankenburg and to a lesser extent, Eerste River when used as source of irrigation, thereby risking the transfer of potentially harmful organisms, present in the rivers as result of faecal pollution, to the surface of fresh produce. / AFRIKAANSE OPSOMMING: Suid-Afrika stuur tans af op 'n dreigende water krisis. Klimaatsverandering tesame met 'n spoedig groeiende bevolking het gelei tot 'n aansienlike vermindering in die land se varswaterbronne terwyl veranderende reënvalpatrone daartoe bygedra het dat talle boere al hoe meer afhanklik geword het van oppervlakvarswaterbronne as hul hoof-besproeïngsbron. Verstedeliking, armoede asook verouderde en onvoldoende infrastrukture het egter bygedra tot die besoedeling van baie van hierdie oppervlakvarswaterbronne. Gevolglik is meeste boere genoodsaak om klaar te kom met besproeïngswater van, nie net onaanvaarbare mikrobiese kwaliteit nie, maar dikwels water wat gekontamineer is met onbehandelde riool. Hierdie studie was gevolglik daarop gemik om die impak van die mikrobiologiese kwaliteit van besproeïngswater op die veiligheid van vars groente en vrugte te bepaal. Standaard mikrobiologiese metodes vir die bepaling van indikator organismes soos totale en fekale kolivorms, E. coli en enterococci asook potensiële patogene wat Salmonella, Listeria en Staphylococcus insluit, was gebruik om die mikrobiese lading by drie verskillende punte (P1, P2 en P3) in die Plankenburg en Eerste Rivier te bepaal. Chemiese parameters soos pH, alkaliniteit, konduktiwiteit en Chemiese Suurstof Behoefte was ook bepaal maar geen korrelasie kon tussen hierdie eienskappe en die mikrobiese besoedelingsvlakke getref word nie. Hoë konsentrasies fekale kolivorms en E. coli wat onderskeidelik vanaf 3.1 x 102 tot 7 x 106 kve.100 mL-1 en 2.3 x 102 tot 7 x 106 kve.100 mL-1 gestrek het en gereeld die voorgeskrewe riglyne van onderskeidelik ≤1 000 (WHO, 1989) en ≤4 000 kve.100 mL-1 (DWAF, 2008) oorskry het, was by al drie punte gevind. Hierdie resultate het gedui op fekale besoedeling wat gevolglik met 'n hoë gesondheidsrisiko geassosieer kon word. Hierdie risiko was bevestig deur die teenwoordigheid van talle potensiële patogene, soos Aerococcus viridans, Klebsiella, Listeria monocytogenes en Salmonella typhimurium, wat vanaf al drie punte geïsoleer was. Die oordrag van organismes vanaf die besoedelde riviere na vars vrugte en groente (groen bone en druiwe) was bepaal deur die mikrobiese lading in die Plankenburg en Eerste Rivier te vergelyk met dié verkry vanuit die besproeïngswater en vanaf groen bone wat besproei was met hierdie water. Fekale kolivorms, E. coli, Aerococcus viridans, Enterobacter aerogenes, Klebsiella, L. innocua, L. grayi, L. monocytogenes en Staphylococcus aureus was vanaf al drie die monster tipes geïsoleer. Hierdie resultate het gedui op eenderse mikrobiese populasies in al drie bronne en het daarom die moontlike oordrag van patogene bevestig. Die opbou van organismes as gevolg van veelvuldige besproeïngsessies aan die oppervlak van groen bone was bevestig deur die toename in fekale kolivorm konsentrasie vanaf 'n begin telling van nul tot 'n maksimum konsentrasie van 44 000 kve.100 mL-1. Laastens was mikrobiologiese bron naspeurbaarheidstegnieke soos multi-antibiotika weerstandbiedende profiele en die API 20E klassifikasie sisteem gebruik om individuele genotipe en fenotipe profiele van die 105 fekale isolate saam te stel. Numeriese klassifikasie sisteme was gebruik om die isolate op grond van ooreenkomste tussen hul individuele fenotipiese en genotipiese karaktereienskappe te groeppeer. 'n Hoë mate van ooreenkomstigheid sal dan daarop dui dat isolate van dieselfde besoedlingsbron afkomstig is en gevolglik die oordrag van organismes vanaf besproeïngswater na vrugte en groente bevestig. Onderskeidelik 93 en 98% van die fekale isolate het daarop gedui om weerstandbiedend te wees teen beide 5 en 30 μg Vancomycin. Die meerderheid isolate (82%) het ook 'n mate van weerstand teenoor Erythromycin (15 μg) en Ampicillin (25 μg) getoon met inhibisie sones ≤4 mm. Isolate was ook sensitief teenoor Ciprofloxacin (1 en 5 μg), Ofloxacin (15 μg), Ceftriaxone (30 μg) en Cefotaxime (5 μg). Hierdie antibiotikums was in staat om die groei van onderskeidelik 79.8, 93.3, 79.8, 88.5 en 71.2 % van die isolate te inhibeer. Alhoewel resultate 'n hoë mate van variasie tussen isolate van dieselfde spesie getoon het was dit nogtans moontlik om 35% van die isolate saam te groeppeer op grond van ooreenstemmende genotipe en fenotipe profiele. Meer as 'n derde van die fekale isolate wat vanaf die oppervlakte van die groente en vrugte geïsoleer was, was afkomstig vanaf fekale besmetting in die besproeïngswater. Die oordrag van potensieël patogene organismes vanaf besoedelde riviere na vars vrugte en groente tydens besproeïng was sodoende bevestig. 'n Hoë gesondheidsrisiko was gevolglik gekoppel aan die gebruik van water vanaf die Plankenburg Rivier, en in 'n minder mate die Eerste Rivier, as bron van besproeïngswater. / Water Research Commission / National Research Foundation

Phthalate esters (PEs) belong to a class of organic compounds used as plasticisers in plastic materials such as polyvinyl chloride (PVC), polypropylene (PP), polyethylene terephthalate (PET) and so on, including those used in the food packaging industry. Phthalate plasticisers are not chemically bound to plastic materials and hence, migrate into items such as foodstuffs they house. The study aimed at investigating the prevalence of selected phthalate esters from plastic wrappers into food as well as the presence of food and/or pathogenic microorganisms. Plastic-wrapped cheese, vienna sausages and polony samples purchased from commercial stores in the four regions of Pretoria (Tswane), South Africa, were analysed for the presence of plasticisers; di-2-ethylhexyl adipate (DEHA), di-n-butyl phthalate (DnBP), benzyl-butyl phthalate (BBP), di-butyl phthalate (DBP) and dimethyl phthalate (DMP). Soxhlet extraction using hexane with florisil column cleanup was carried out. Analysis of PEs was by Gas Chromatography-Flame Ionization Detection (GC-FID). Microbiological investigations were performed using standard methods. The concentrations of PEs detected in food samples ranged from below detection limit (bdl) to 4.7003 μg/kg. However, DBP, DMP and BBP were predominantly present with more PEs detected in cheese compared to polony and vienna. In polony samples, DBP levels ranged from 0.0412 to 0.611μg/kg, in cheese, ranged from 0.049 to 0.256 μg/kg and in vienna DBP ranged from 0.074 to 0.209 μg/kg. The phthalate DMP ranged from 0.072 to 4.700 μg/kg in cheese, 0.056 to 0.241 μg/kg in polony and 0.092 to 0.816 μg/kg in vienna. The DEHA detected in cheese and polony was 0.120 μg/kg and 0.075 μg/kg respectively and no DEHA was detected in vienna sausages. For microbiological analysis, the total microbial activity (TMA) ranged from 6.8 x 104 to 1.03 x 108 cfu/g; coliforms ranged from no growth to 2.62 x 106 cfu/g; yeast ranged from no growth to 1.49 x 107 cfu/g; and mould ranged from no growth to 9.2 x 104 cfu/g. The results revealed that microbial activity was high in each sample type but revealed the absence of pathogens. Results revealed incidences of PEs in foods wrapped or packaged in plastics, which gave cause for concern and showed the need for proper monitoring and inspection of the levels of organo-microbial entities in the South African food wrapped in plastic wrappers. / Environmental Sciences / M.Sc. (Environmental Science)

The contamination of street vended vegetables may occur through the usage of manure and contaminated irrigation water, and the consumption of these vegetables, such as ready-to-eat salads, can cause foodborne diseases in consumers. The objective of this study was to investigate the Enterobacteriaceae diversity in vegetables sold at informal markets in the Johannesburg Metropolis. A total of 201 vegetable samples were purchased from randomly selected street vendors from different regions in the Johannesburg Metropolis and analysed for aerobic growth count and Enterobacteriaceae contamination using Plate Count Agar (PCA), and violet red bile glucose agar (VRBGA), respectively. The diversity of bacterial isolates was analysed using sequencing and phylogenetic analysis. The aerobic bacterial growth counts of vegetables from all the regions ranged from 7.66(±0.759) to 8.37(±0.347) log10 cfu/g and the mean aerobic growth counts of vegetables from Soweto and Yeoville were significantly different (p ≤ 0.05) from those of the other regions, but were not significantly (p > 0.05) different across different vegetable types. The Enterobacteriaceae growth counts in vegetables from all the regions ranged from 5.05 (±0.647) to 5.45 (±0.693) log10 cfu/g. The mean Enterobacteriaceae growth counts of vegetables were not significantly (p > 0.05) across each region and different vegetables types. The predominant Enterobacteria genera were Serratia (35%), followed by Hafnia (21%), Aeromonas (17%), and Pseudomonas (5%). In conclusion, this study shows that the vegetables sold at the informal markets in the Johannesburg Metropolis have high aerobic bacterial growth and Enterobacteriaceae contamination due to poor hygiene practices. The dominant Enterobacteriaceae genera isolated are Aeromonas, Hafnia, Serratia, and Pseudomonas, which could be opportunistic pathogens. It is recommended that the Department of Health improves vending and sanitation facilities, to prevent cross contamination. / Life and Consumer Sciences / M. Sc. (Life Sciences)

Food is one of the main routes by which xenobiotic (synthetic) chemicals enter the body of man and wildlife. The routes could be from wrappers in which the foods are presented with possible transfer of the compounds to consumers, hence need for regular screening. The research work is aimed at investigating possible prevalence of phthalate esters in selected foods (cheese, polony and vienna) and their plastic wrappers from commercial stores in Tshwane metropolis. Food samples were purchased from selected stores, taken to the laboratory and stored at 4oC until analysed. Analysis was done by soxhlet extraction while determination and quantification of phthalates was carried out using Gas Chromatography-Flame Ionization Detection (GC-FID). Quality assurance of the process was by standard addition of the phthalate ester standards. Results obtained revealed good chromatographic separation of the analysed esters which ranged from 5.55 min for Dimethyl phthalate (DMP) to 8.96 min for Benzylbutyl phthalate (BBP). Instrumental detection limit of the esters varied from 0.03 - 0.05 μg/kg. The percentage recovery of the phthalate esters ranged from 75 – 90% from spiked cheese samples; 33 – 66% from spiked polony samples and 69 – 99% from spiked vienna samples. These recoveries are quite acceptable and applicable to the analysis and quantification of the compounds in the samples with the exception of Dibutyl phthalate (DBP) (33%); DMP (34%) and BBP (46 %) in polony samples. Results from chromatographic quantification revealed the absence of or non-detection of most of the analysed phthalate esters in the selected food samples. However, level of 0.031 μg/kg of BBP - 0.816 μg/kg of DMP were obtained in some of the analysed samples. / Environmental Sciences / M.Sc. (Environmental Science)

Food is one of the main routes by which xenobiotic (synthetic) chemicals enter the body of man and wildlife. The routes could be from wrappers in which the foods are presented with possible transfer of the compounds to consumers, hence need for regular screening. The research work is aimed at investigating possible prevalence of phthalate esters in selected foods (cheese, polony and vienna) and their plastic wrappers from commercial stores in Tshwane metropolis. Food samples were purchased from selected stores, taken to the laboratory and stored at 4oC until analysed. Analysis was done by soxhlet extraction while determination and quantification of phthalates was carried out using Gas Chromatography-Flame Ionization Detection (GC-FID). Quality assurance of the process was by standard addition of the phthalate ester standards. Results obtained revealed good chromatographic separation of the analysed esters which ranged from 5.55 min for Dimethyl phthalate (DMP) to 8.96 min for Benzylbutyl phthalate (BBP). Instrumental detection limit of the esters varied from 0.03 - 0.05 μg/kg. The percentage recovery of the phthalate esters ranged from 75 – 90% from spiked cheese samples; 33 – 66% from spiked polony samples and 69 – 99% from spiked vienna samples. These recoveries are quite acceptable and applicable to the analysis and quantification of the compounds in the samples with the exception of Dibutyl phthalate (DBP) (33%); DMP (34%) and BBP (46 %) in polony samples. Results from chromatographic quantification revealed the absence of or non-detection of most of the analysed phthalate esters in the selected food samples. However, level of 0.031 μg/kg of BBP - 0.816 μg/kg of DMP were obtained in some of the analysed samples. / Environmental Sciences / M. Sc. (Environmental Science)