Isolation of Listeria monocytogenes from milk

Abstract

A total of 121 milk samples comprising 50 individual cow milk of an organised dairy farm, 16 individual cow milk of a private dairy farm, 35 pasteurized bulk tank milk and 20 non-pasteurized bulk tank milk were subjected to detailed bacteriological examination for the isolation of Listeria monocytogenes. Out of 16 Listeria isolates recovered. 7 were of L. monocytogenes (organised dairy farm-2, private farm-4 and non-pasteurized bulk tank milk-1) and remaining 9 isolates belonged to other Listeria spp (organised dairy farm-3, private dairy farm-4, non-pasteurized bulk tank milk-2). Pathogenicity testing of L. monocytogenes isolates revealed 6 isolates to be pathogenic. The antibiogram studies showed that L. monocytogenes were sensitive to doxcycline, ampicillin, ciprofloxacin and penicillin. The presence of pathogenic L. monocytogenes in milk may cause serious health problem to human.