Incidence and genetic variability of Listeria species from three milk processing plants |
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Authors: | Swapnil Doijad SB Barbuddhe Sandeep Garg Sushanta Kalekar Jenney Rodrigues Dilecta D’Costa S Bhosle Trinad Chakraborty |
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Affiliation: | 1. Department of Microbiology, Nicolaus Copernicus University in Toruń, L. Rydygier Collegium Medicum in Bydgoszcz, 9 M. Sk?odowska-Curie St., 85-094 Bydgoszcz, Poland;2. Department of Food Hygiene and Consumer Health, Wroc?aw University of Environmental and Life Sciences, 31 C.K. Norwid St., 50-375 Wroc?aw, Poland;3. Department of Microbiology and Food Technology, UTP University of Science and Technology, 6 Bernardyńska St., 85-029 Bydgoszcz, Poland |
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Abstract: | The presence of Listeria in three milk processing environments as a potential source of milk contamination was assessed. Swab samples (n = 210) taken from milk processing plants were examined. Sample sites included the milk processing equipment, besides areas handling raw and pasteurized milk. The USDA Listeria-selective enrichment procedure was used to process the samples. Forty one (19.52%) Listeria isolates were recovered. The isolates were further subjected to biochemical and genotypic characterization. Out of 41 isolates, 16 (7.62%) were confirmed as Listeria monocytogenes, 2 (0.95%) as L. ivanovii, 19 (9.05%) as L. innocua. 1 (0.48%) as L. seeligeri and 3 (1.43%) as L. grayi. All the L. monocytogenes isolates were positive for the hlyA gene. PCR based serotyping revealed all L. monocytogenes to be of 1/2a, 1/2c, 3a and 3c serovar group. AscI and ApaI restriction analysis yielded four PFGE clusters for 16 L. monocytogenes isolates obtained from raw milk collector, milk silos, buttermilk mixer, cheese and other milk product processor. No predominant PFGE cluster was observed among these L. monocytogenes isolates. The main sources of L. monocytogenes were found to be raw milk collector and milk silos. In the present study L. monocytogenes was isolated from milk and milk products processing plants which could cross-contaminate the processed products and may possess a potential threat to public health. |
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