Abstract

Listeria sp. is one of the most important zoonotic diseases which cause dangerous illness. It consists of six species but the most important one is Listeria monocytogenes,which is a major concern for the food industry. Listeria is ubiquitous in dairy farms and it is isolated from cows’ milk. The purpose of this study is to identify Listeria spp. in 986 raw whole cow milk samples by cultural method and biochemical tests. From April 2010 to May 2011, totally 986 raw cow samples were collected. A total of 25 samples (2.53%) were contaminated by Listeria spp.: 2.02% by Listeria monocytogenes and 0.51% byListeria innocua. In other words, 80% of infested samples was due to Listeria monocytogenes. Also it was seen that 92% of infested samples occurred in fall season. Our results show that contamination by Listeria spp. is commonly related to environmentally special food and season, because silos feeding is done in fall. Our finding suggests more studies on thermal resistance and improvement in preparing silos.

Key words: Listeria species, raw milk, cow, Iran.