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- ItemInfluence of Organic Material and Biofilms on Disinfectant Efficacy Against Listeria monocytogenes(ISEKI-Food Association (IFA), 2012-04-18) Nyati, H.; Beumer, R.; Van der Veen, S.; Hazeleger, W.; Abee, T.The effects of organic material and biofilm formation on the efficacy of Suma Tab D4 chlorine tablets and Suma Bac D10 quaternary ammonium compound (QAC) against Listeria monocytogenes was determined in suspension and on stainless steel and polystyrene surfaces according to standard disinfectant test methodology. Exposure to 200 and 740 mg L-1 QAC and to 150 mg L-1 active chlorine resulted in a> 5.0 log10 CFU mL-1 and> 5.0 log10 CFU/coupon reduction of six L. monocytogenes strains within one minute, in suspension tests, and on stainless steel surfaces, respectively. Additionally, there was a reduction by as much as 5 log10 CFU/coupon or 5 log10 CFU/well of reference strains EGDe and Scott A biofilms within five minutes on stainless steel and polystyrene surfaces. Organic material, added as bovine serum albumin at 0.3%(w/v) completely prevented the inactivation of L. monocytogenes in 150 mg L-1 chlorine, while reductions of only 0.6+-0.1 log10 CFU mL-1 were recorded in the presence of UHT milk at 3%(v/v). In contrast, reductions of 5 log10 CFU mL-1 were recorded within one minute on exposure to 740 mg L-1 QAC in the presence of 0.3%(w/v) bovine serum albumin and within two minutes in the presence of 20%(v/v) UHT milk. Although Suma D4 chlorine tablets and Suma Bac D10 QAC are effective listericidal agents at recommended concentrations, Suma Tab D4 chlorine efficacy against L. monocytogenes is impaired by the presence of low concentrations of organic material, while Suma Bac D10 QAC maintains its listericidal activity in high organic loads.
- ItemMolecular Characterization of Aflatoxigenic Aspergillus species in dried Traditional foods in Zimbabwe(Society of Education, 2014-01-10) Dangwa, N.; Mwenje, E.; Dhlamini, Z.; Siwela, A.HThe presence of aflatoxin producing Aspergillusspp in sixty samples of six selected traditional foods sold on the Bulawayo open market in Zimbabwe was investigated. Ten samples of each of the following commodities were bought from the market; dried groundnuts, dried cowpeas, dried maize, dried cowpea leaves, dried mopane worms and dried Cleome gynandra leaves and analysed for the presence of aflatoxigenic aspergillus. Moisture content of the samples was determined and another portion of the samples was plated on petri dishes containing Sabouraud Dextrose Agar (SDA) and incubated at 28 C. A total of 35 isolates was obtained and these were characterised according to their morphology as well as the type of aflatoxins they produced as determined by thin layer chromatography. Four distinct morphological groups were found and they were classified as Aspergillu sparasiticus (57%); Aspergillusniger (17%); Aspergillus tamarii (17%) and Aspergillusflavus (8%). These results were validated by using DNA primers of the structural genes, aflD (nor-1), aflM (ver-1) and aflP (omt-1) and the regulatory gene aflR to discriminate between aflatoxigenic and nonaflatoxigenic strains after amplifying DNA of the fungal strains. None of the isolates produced all the four genes involved in the aflatoxin biosynthetic pathway although they had shown positive results on the biochemical tests. Out of the 35 isolates obtained, 18 of them were aflatoxigenic and these isolates were from mopane worms (9), cowpeas (4), groundnuts (3) and Cleome gynandra (1). This investigation showed that dried traditional foods in Zimbabwe were contaminated by the aflatoxigenic fungus, Aspergillus, probably due to improper drying of the commodities, coupled by prevailing environmental conditions from packaging to the selling points.
- ItemToxicological effects of technical grade and formulated pesticides on esterase activity in freshwater snails H. duryi and L. natalensis.(Scholars Research Library, 2015) Basopo, N.; Naik, Y.SWe investigated the effects of formulated pesticides on non target organisms in order to evaluate the role played by inert ingredients in the toxicity of agrochemicals. The effects of both technical grade and formulated pesticides on esterase activity of two freshwater snail species Helisoma duryi and Lymnaea natalensis was investigated. Snails from both snail species were exposed to chlorpyrifos, dimethoate, carbaryl, lambda cyhalothrin, deltamethrin or mancozeb for 72 hours. Some of the snails were exposed to technical pesticides while others were exposed to the commercial forms of the pesticides. After the exposure duration post-mitochondrial supernatants of whole snail homogenates were prepared and used to measure choline and non-cholinesterase activity using substrates, acetylthiocholine iodide or α-naphthyl acetate respectively. The results showed that both formulated and technical grade pesticides significantly inhibited esterase activity. The inhibition observed in snails exposed to formulated commercial pesticides was twofold or more when compared to inhibition observed in snails exposed to technical grade pesticides and this was attributed to presence of inert ingredients in formulated pesticides. The enhanced inhibition of esterase activity observed in snails exposed to formulated pesticides indicates that aquatic organisms are potentially at risk to the toxic effects of the unspecified ingredients which are part of formulated pesticides.
- ItemVirulence gene profiles of avian pathogenic Escherichia coli isolated from chickens with colibacillosis in Bulawayo, Zimbabwe(Scielo, 2015) Mbanga, J.; Nyararai, Y.O.Colibacillosis, a disease caused by avian pathogenic Escherichia coli (APEC), is one of the main causes of economic losses in the poultry industry worldwide. This study was carried out in order to determine the APEC-associated virulence genes contained by E. coli isolates causing colibacillosis in chickens. A total of 45 E. coli isolates were obtained from the diagnostics and research branch of the Central Veterinary Laboratories, Bulawayo, Zimbabwe. These isolates were obtained from chickens with confirmed cases of colibacillosis after postmortem examination. The presence of the iutA, hlyF, ompT, frz, sitD, fimH, kpsM, sitA, sopB, uvrY, pstB and vat genes were investigated by multiplex polymerase chain reaction (PCR) assay. Of the 45 isolates, 93% were positive for the presence of at least one virulence gene. The three most prevalent virulence genes were iutA (80%), fimH (33.3%) and hlyF (24.4%). The kpsM, pstB and ompT genes had the lowest prevalence, having been detected in only 2.2% of the isolates. All 12 virulence genes studied were detected in the 45 APEC isolates. Virulence gene profiles were constructed for each APEC isolate from the multiplex data. The APEC isolates were profiled as 62.2% fitting profile A, 31.1% profile B and 6.7% profile C. None of the isolates had more than seven virulence genes. Virulence profiles of Zimbabwean APEC isolates are different from those previously reported. Zimbabwean APEC isolates appear to be less pathogenic and may rely on environmental factors and stress in hosts to establish infection.
- ItemCloning Cellulase Genes from Victoria Falls Rainforest Decaying Logs Metagenome(Sciendo, 2024) Nyathi, M,; Dhlamini, Z.; Ncube, T.The Victoria Falls rainforest is a protected site whose forest floors harbor a host of cellulolytic microorganisms involved in biomass degradation. This study collected decaying logs and soil from the rainforest for bioprospecting cellulases from their metagenomes. Metagenomic DNA was isolated from the compound sample. Degenerate cellulase primers were used to amplify cellulase genes in the metagenome. The resulting amplicons cloned into Z-competent Escherichia coli DH5α were analyzed by functional screening for the production of cellulase extracellularly. Functional screening of the clones resulted in one clone (Clone-i) testing positivefor extracellular cellulase production. Submerged fermentation of Clone-i was carried out for cellulase production. The cellulases were characterized to determine their activity’s optimum pH and temperature. The diversity of the cellulases produced by Clone-i was determined. Clone-i’s optimum enzyme activity was observed after 72 hours of incubation at 50°C and pH 5. Clone-i produced 80% more exoglucanases as compared to endoglucanases. The cel- lulolytic Clone-i’ isolate shows Victoria Falls rainforest’s potential as an enzyme bioprospecting site, reflecting that metagenomics is a valuable tool in microbial ecology.