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Medical Biochemistry

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Browsing Medical Biochemistry by Author "Bester, Linda Antionette."

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    Antibiotic resistance in the food chain : a case study of Campylobacter spp. in poultry.
    (2013) Bester, Linda Antionette.; Essack, Sabiha Yusuf.
    The sub-therapeutic use of antibiotics for growth promotion in food animal production, has engendered substantial debate on the dissemination of antibiotic resistance via the food chain, specifically, the probability of antibiotic use in food production creating a reservoir of resistant bacteria and/or resistance genes that may spread to humans thereby limiting the therapeutic value of antimicrobial drugs. In the absence of any surveillance programme on food-borne bacteria in South Africa, this study focussed on Campylobacter spp. in poultry and encompassed a literature review on the prevailing debate on the dissemination of antibiotic resistance via the food chain, a phenotypic observational study on the prevalence and antibiotic resistance profiles of Campylobacter spp. isolated within and across different poultry farming systems and a genotypic component that covered identification methods, plasmid profile determination and strain typing. Identification methods for Campylobacter spp., viz, biochemical tests and matrix assisted laser desorption ionization- time of flight (MALDI-TOF) mass spectrometry was compared to the PCR which is considered the gold standard as a molecular method of identification. The MALDI-TOF was shown to be superior to the biochemical tests for the identification of C. coli but equivalent to the biochemical tests for C. jejuni. Of the 363 samples collected in total, the frequency of thermophilic Campylobacter was 68 % in rural farms (or informally reared poultry), 47 % in both commercial free-range and industrial broilers and the highest in industrial layers at 94 %. Antibiotic resistance analysis showed that isolates from the rural farming systems were significantly (P < 0.01) more susceptible to ciprofloxacin, tetracycline and erythromycin when compared to the other farming systems. Significant (P < 0.001) antibiotic resistance differences were detected between broilers (5 - 8 week lifespan), and layers (36 - 52 week lifespan) for gentamicin, ciprofioxacin and tetracycline. Plasmids were fonnd be harboured by isolates in all the farming systems; in 84 % of isolates from free-range broilers, 77 % of isolates from industrial broilers, 83 % of isolates from industrial layer hens and 75 % of isolates from the rural farming system. The PFGE genotyping of 42 Campylobacter isolates generated 39 SmaI types. Substantial and substantive genetic diversity was observed between and within farming systems. The lack of correlations amongst the parameters within and between farming systems attested to the diversity and complexity of phenotypes and genotypes and indicated de novo evolution in response to antibiotic selection pressure and animal husbandry practices.
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    An investigation into marine bacterial species found in shark mouths in the Indian Ocean and their implications for human health.
    (2015) Ramlakhan, Yathisha.; Chuturgoon, Anil Amichund.; Phulukdaree, Alisa.; Bester, Linda Antionette.; Singh, Sanil Duleep.
    There is an ever increasing amount of pollution and waste being released into the environment. This is due to the increase in population, urbanisation and people migrating into cities. Approximately 2.4 billion people living in urban and rural areas have no access to basic sanitation. In the next 20 years, there will be a further increase of 2 billion people who will lack basic sanitation. In developing countries, 90% of untreated sewage is released into rivers, lakes and coastal waters. Apart from sewage, waste such as petroleum products, heavy metals and organochlorine also contribute to marine pollution. Companies that manufacture sugar/artificial sweeteners etc. and farming activities that utilize fertilizers for crops can cause eutrophication, as un-used fertilizers get washed into rivers. The marine water is a different environment to other aquatic and terrestrial environments. This then forces microbes to adapt, so they can be able to survive in the marine environment. The difference in the marine environment allows for the production of distinct bioactive metabolites such as secondary metabolites. These secondary metabolites come from algae and marine bacteria and these secondary metabolites are then exclusive to the marine waters. These secondary metabolites can be used for medical purposes, cosmetics, personal-care products etc. There is a huge problem with antibiotic resistance and research needs to be done to solve this resistance issue. Two common bacterial strains were isolated and identified from the mouth of sharks. The bacteria were identified as Bacillus cereus and Vibrio alginolyticus. They were isolated and cultured in broth for 3 days, till they reached the log phase of growth. The broth was then extracted for metabolites which the bacteria produced, using ethyl acetate. These metabolites were tested for cytotoxicity in the human liver hepatocellular carcinoma (Hep G2) cells. The concentrations that were determined to cause 50% cell death (IC50) in the cell viability assay on Hep G2 cells were 0.764 mg/ml and 0.918 mg/ml for B. cereus and V. alginolyticus, respectively. These values were then used for subsequent assays. Antibacterial testing was done for the bacterial extracts of Bacillus cereus and Vibrio alginolyticus. There was no antibacterial activity against Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923 and Pseudomonas aeruginosa ATCC 27853. Assays that used flow cytometry was used to show if apoptosis/necrosis occurred. These were assays such as Annexin V and propidium staining. While assays that used luminometry showed the levels of ATP and determined whether apoptosis of the cells occurred. These were assays such as the ATP assay, mitochondrial depolarisation assay and determination of the caspase activities of caspase 3/7, 8 and 9. Additional assays, like the comet and TBARS assays, were done to show DNA fragmentation and oxidative stress of the cells, respectively. The results for the Annexin V/ propidium staining showed the control had a mean of 11.20 ± 1.0. Extract 1 (20.83 ± 0.8737) and extract 2 (25.37 ± 1.050) showed a higher percentage when compared to the control. Extract 2 was significant against the control (p<0.0273). For propidium staining, the control had a mean of 6.033 ± 0.4524. Extracts 1(11.57 ± 1.387) and 2 (11.43 ± 0.3215) showed a higher percentage when compared to the control. The Annexin V and propidium staining suggested that extract 1 and 2 had undergone both apoptosis and necrosis. For luminometry assays, the ATP assay showed that the control had a mean of 1.83x106 ± 5.82x104. Extracts 1 (1.5x106 ± 9.4x104) and extract 2 (1.4x106 ± 8.3x104) showed a decrease in ATP with reference to the control. In the mitochondrial depolarisation assay, the control had a mean of 14.83 ± 1.350. Extracts 1 (30.57 ± 0.75) and extract 2 (20.53 ± 8.56) showed a decrease in polarisation with reference to the control. For caspase 8 analysis, the control, extract 1 and extract 2 had means that were 4.23x104 ± 3.37x103, 52x103 ± 10.1x103 and 40x103±5.2x103, respectively. For caspase 9 analysis, the control, extract 1 and extract 2 had means that were 8.6x104 ± 4.6x103, 5.6x104 ± 4x103and 9.6x104 ± 5.6x104, respectively. The caspase 3/7 analysis showed that the control, extract 1 and extract 2 had means of 4.4x103 ± 0.57x103, 5.5x103 ± 0.19x103 and 5.8x103 ± 2 x103, respectively. Caspase 3/7 showed that apoptosis had occurred with the cells for all extracts used. Extract 1 showed a high caspase activity for caspase 8. This suggested that it followed the extrinsic pathway of apoptosis. Extracts 2 showed a high activity for caspase 9 which suggested that it followed the intrinsic pathway of apoptosis. The comet assay showed that the means of the control, extract 1 and extract 2 were 35.91 ± 21.93, 75.85 ± 11.43 and 60.48 ± 11.86, respectively. The extracts were significantly higher than the control (extract 1 and 2 p<0.0001). Extract 1 and 2 were compared to each other and had shown a significance between them (p<0.0001). The TBARS assay obtained the following MDA concentrations for the control, extract 1, extracts 2, negative and positive samples: 0,137, 0,132, 0,150, 0,088 and 20,502, respectively. The MDA concentration gives an indication of oxidative stress of the cells. From the cell viability assay, the secondary metabolites produced by B. cereus needed a lower concentration of extract to determine an IC50 value. This suggested that the secondary metabolites produced by B. cereus were more toxic than the secondary metabolites produced by V. alginolyticus. This was then further supported by assays such as mitochondrial depolarisation and the comet assay. The secondary metabolites that could be the reason why there were apoptosis and necrosis, are the toxins the bacteria produce. This is the enterotoxin or cereulide produced by B. cereus and TLH by V. alginolyticus. However, further studies need to be done to confirm if these toxins are the cause of cell death.