Detection of Listeria monocytogenes from milk and milk products in Puducherry

Abstract

Food borne diseases encompass a wide array of illnesses and are a growing public health hazard worldwide. Listeria monocytogenes causes food borne listeriosis, which is a relatively rare but serious emerging disease with high fatality rates among susceptible population. This study was conducted to detect the presence of L. monocytogenes from milk and milk products in Puducherry. A total of 200 samples including 100 raw milk, 50 pasteurized milk and 50 ice cream samples were collected from different retail shops in Puducherry. Results revealed 4 samples (4%) from raw milk and 1 sample (2%) from ice cream were suspected for L. monocytogenes. All the suspected isolates were confirmed as L. monocytogenes by various cultural and morphological examination. Also, all were positive for hlyA gene by polymerase chain reaction which is confirmative for L. monocytogenes. Further biofilm production assay revealed two isolates from raw milk were moderate biofilm producers (40%) and three isolates which included two from raw milk and one from ice cream were weak biofilm producers (60%). Antibiotic resistance profiling of the isolates showed an increased resistance to gentamicin, vancomycin and penicillin G which are commonly used in the treatment of listerial infection. This study directs the need for proper hygienic measures before and after collection of milk, processing and proper storage of milk and dairy products to limit the contamination level.