SOURCES AND ROUTES OF CONTAMINATION OF RAW-MILK WITH LISTERIA-MONOCYTOGENES AND ITS CONTROL

To identify the source of contamination of raw bulk milk with Listeria , we attempted to isolate the bacteria from various samples such as ca ttle-related samples, bulk storage tanks and the environments on three farms. On farms A and B, Listeria monocytogenes was repeatedly isolat ed from raw milk, while on farm C, it was scarcely isolated from it. O n the former farms, Listeria was detected in cattle-related samples an d the environments. On the other hand, only one fecal sample on the la tter farm was Listeria-positive, Especially, we demonstrated that the bulk tank on farm A was contaminated with L. monocytogenes. Then, L. m onocytogenes was controlled by continuously washing the bulk tank on f arm A with alkaline detergent.