Isolation and Characterization of Listeria monocytogenes from Raw Milk in Durg District of Chhattisgarh

The work was conducted to determine the total aerobic plate count of milk samples, isolation of the Listeria spp. and to determine their pathogenicity. Raw milk samples, collected from the dairies located in Durg district, showed mean APC of 24 x10 cfu/ml (6.380 log 10 cfu/ml). Cultural examination of 100 raw milk samples revealed an overall 6% prevalence of Listeria spp. and only L. monocytogenes was isolated from milk. All the Listeria isolates exhibited a typical α-heamolysis with narrow zone on sheep blood agar. The haemolytic listerial isolates in CAMP test showed enhancement of haemolytic zone and developed purulent conjunctivitis in Anton’s test. Similarly, L. monocytogenes isolate in embryonated chicken eggs showed severe haemorrhages in liver, heart and surface of embryo along with conspicuous thickened CAM.