Browsing by Author "Wimalasekara, S.G.M.R.L."

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    The antagonistic effect between Abamectin degrading bacteria, Staphylococcus nepalensis and Bacillus thuringiensis
    (Faculty of Science, University of Kelaniya, Sri Lanka, 2020) Wijesinghe, J.M.M.; Wimalasekara, S.G.M.R.L.; Perera, T.W.N.K.
    Basic ecological concepts govern the composition and the functional relationships among microorganisms of a particular ecosystem of interest. Antagonism is one such functional relationship among bacteria. A bacterium that is antagonistic to another is capable of producing molecules with different structures, cellular targets, spatial range, and mode of action that are harmful to other organisms in the same niche. Even though the antagonism is beneficial to the survival of a bacterium when considering processes such as bioremediation having multiple bacteria capable of performing the same or cooperative objectives, this effect is detrimental. Staphylococcus nepalensis and Bacillus thuringiensis are two Abamectin degrading bacteria. To test whether there is an antagonistic interaction between S. nepalensis and B. thuringiensis, the growth compatibility assay was performed using salt yeast extract (MSYE) agar plates supplemented with Abamectin (25 mgL-1 ). Parallel streak lines were made using previously isolated, Abamectin degrading, S. nepalensis and B. thuringiensis cultures and their identification was confirmed by biochemical tets. Plates were incubated for 72 hours at 37 °C. Growth inhibition zone encircling the S. nepalensis streak was observed after the incubation period. Results from this test were confirmed by measuring the Optical Density (OD) measurements at 600 nm, of MSYE broth cultures of S. nepalensis, B. thuringiensis and a combination of both. Inoculated broths were incubated in a shaker incubator (150 rpm, at 30 °C) for 72 hours, and growth was monitored by measuring OD at 24-hour intervals. OD measurements 72 hours after the inoculation (S. nepalensis - 0.19133, B. thuringiensis - 0.12500, Mixed culture - 0.12000) indicated the fact that the growth of pure cultures is higher, compared to that of the mixed culture of both organisms. Accordingly, the results of OD measurements demonstrated an antagonistic effect between S. nepalensis and B. thuringiensis. As claimed by the results of both tests it is not applicable to use them together to treat Abamectin-associated pollutions. They can still be successfully applied individually as pure cultures. However, both organisms should not be applied to the same site, at the same time, as it would be inimical towards their bioremediation capability.
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    A preliminary microbiological study of chicken-based short-eat food in Kadawatha, Sri Lanka
    (Faculty of Science, University of Kelaniya, Sri Lanka, 2016) Wimalasekara, S.G.M.R.L.; Gunasena, G.D.D.K.
    Foodborne disease outbreaks caused by microbiological hazards are a growing public health concern in all around the world. It results in a significant number of deaths and hospitalizations in each year. According to the ‘Weekly Epidemiological Report: A publication of the Epidemiology Unit’ of Ministry of Health (2013: Vol. 40, No. 49), fast short-eat food are identified as a prominent source of foodborne illnesses as they do not undergo any effective treatment to ensure food safety prior to consumption. Therefore, the present study was conducted to determine the microbiological quality and safety of fast food sold in highly urbanized Kadawatha city, Sri Lanka. A total of six chicken based short-eat food products obtained from recognized restaurants at Kadawatha city were analyzed for Total viable count (TVC), Total coliform count (TCC), Escherichia coli count (ECC), Staphylococcus aureus count (SAC) and for the presence of Salmonella according to Sri Lanka Standards (SLS:516). The noncompliance of the food samples were determined according to the local microbiological guidelines for fast food by Sri Lankan Standards Institution (SLS:1218). Food, including burger, club sandwich, bread roll sandwich and rotty exceeded the proposed guideline (5 log CFU/g) for TVC and club sandwich found to bear the highest TVC of 7.51 log CFU/g, whereas hotdog with mustard cream had the lowest of 3.05 log CFU/g. All food, except from hotdog with mustard cream were detected TCC exceeding 10 MPN/g indicating cross contaminations by poorly sanitized food contact surfaces, poor quality ingredients and improper waste discard policies. E. coli were present only in burger (4 MPN/g), bread roll sandwich (4 MPN/g) and club sandwich (9 MPN/g) signifying the degree of ignorance from the food handlers for maintaining personal hygiene during food preparation. Further, the statistical analysis of the samples denotes a significant (P < 0.05) correlation between TVC, TCC and ECC. S. aureus was detected in four food samples where the highest SAC of 4.48 log CFU/g found to be in rotty. This may be attributed to extensive handling and temperature abuse during storage. However, Salmonella was not detected in any of the analyzed food. The present study demonstrates that the fast short-eat food implies a potential public health hazard and more importantly, the susceptible population is at a higher risk. Given the higher demand for these foods, it stresses the immediate attention of local authority in the area to emphasize on educating food vendors on the importance of adhering to strict food safety regulations and Food Safety Management Systems (FSMS) to ensure that the standard of the food is best achieved from farm to folk.