Autochthonous microbiota of raw milk with antagonistic activity against Listeria moncytogenesand Salmonella enteritidis

The objective of this study was to detect and identify the autochthonous microbiota of raw milk with antagonistic activity on Listeria monocytogenes and Salmonella Enteritidis. Three hundred sixty colonies isolated from 15 raw milk samples were tested for antagonistic activity for L. monocytogenes and S. Enteritidis using the "spot-on-the-lawn" method. The colonies detected as antagonistic were identified using API 20 Strep. Two types of inhibition were observed: total, characterized by the formation of a well-defined halo around the colony, and partial, with the formation of a diffused halo. Ninety-one (25.3%) colonies presented antagonistic activity for L. monocytogenes and 33 (9.2%) for S. Enteritidis. Most of the antagonistic cultures were lactic acid bacteria, mainly Lactococcus lactis ssp. lactis and Enterococcus faecium. The results indicate that microorganisms in the natural microbiota of raw milk may play an important role in the inhibition of key pathogens in dairy products. This article is an initial study from our group concerning the antagonistic activity of the autochthonous microbiota from raw milk. This activity can explain the low frequency of some pathogens in this food, and these findings were the basis for our current studies concerning the characterization of this activity. For the period of 2006-2008, our group received funds from the National Council for Scientific and Technological Development, Brazil, and the Foundation of Scientific Support from Minas Gerais state, Brazil, for this complete study, aiming to describe the antagonistic microorganisms (phenotypic and genotypic), their antimicrobial productions (identification, characterization and potential) and purification. This article has the importance of supporting similar studies concerning this phenomenon, and proves the necessity of future studies for isolation and characterization of autochthonous microorganisms in milk, with antimicrobial activity, for subsequent utilization in the dairy industry, improving food safety.