INCIDENCE OF LISTERIA SPECIES FROM DAIRY ENVIRONMENTAL SAMPLES
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Date
2020-08-01
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KARNATAKA VETERINARY, ANIMAL AND FISHERIES SCIENCES UNIVERSITY, BIDAR
Abstract
In present study, Listeria count in soil, fodder, dung and feed samples collected from university dairy farm ranged from 2.30 to 3.14 log10cfu/g. Udder swab, pail rinse, pail milk and can milk had Listeria count of 0.30 log count while 0.60 log count observed in chilled milk whereas water, swabs of hand, udder and equipment, pail and can rinses, aseptic milk and pasteurized milk did not show the presence of Listeria. Among 23 isolates of Listeria obtained from dairy environmental samples, Listeria monocytogenes predominated (56.50) followed by Listeria innocua (17.39), Listeria ivanovii (8.70); Listeria seeligeri (4.35) and 13.06 per cent of unidentified Listeria sp. All the 23 Listeria isolates, except L. monocytogenes L16 grew well at 5 C indicating psychrotrophic nature of the isolates. At deep freeze temperature (-18 C), only 9 out of 23 Listeria isolates showed growth indicating the psychrophilic nature of isolates. Among 23 Listeria isolates, 14 numbers of Listeria spp. showed haemolysis, phospholipase and coagulase activities indicating pathogenic nature. Listeria monocytogenes L10 showed highest DMC of 8.95 log10/ml among 23 isolates and used in further studies. Initial viable log count of Listeria monocytogenes L10 in sterile milk 5.95 reached to 8.98 with per cents of 0.30 LA; protein of 1.00, oleic acid of 1.86 and haemolysin of 10 mm diameter at 24 h of incubation at 37
C. L. monocytognes L10 at 3, 4, 5 and 6 viable log counts inoculated into sterile whole milk and stored at 5 C the raise on an average viable log count was by 4, 3, 2 and 1.5 with storage period of 30, 20, 12 and 9 days, respectively based on the curdling of milk. During storage, the percent mean acidity of 0.23, protein reduction by 1.25, developed oleic acid was 1.40. Haemolysin production in L. monocytognes L10 started on half of storage period that reached peak on last day of storage at 5 C.