Occurrence of Listeria monocytogenesand Escherichia coliin Raw Sheep's Milk from Farm Bulk Tanks in Central Italy

For milk hygiene and safety, the milking phase is a critical moment because it is a probable pathway for the introduction of unwanted microorganisms in the dairy chain. In particular, Listeria monocytogenesand Escherichia coliare known as possible microbial contaminants of raw sheep's milk, although extensive knowledge regarding their contamination dynamics on sheep farms is still lacking. This study aimed to examine the occurrence and concentration of these microorganisms in milk samples collected from farm bulk tanks in the region of Lazio (Central Italy) and to investigate the related risk factors. Over a period of 1 year, we collected 372 milk samples from 87 sheep farms and administered a questionnaire to acquire information regarding relevant farm management variables. L. monocytogeneswas not found in any of the samples, which indicates a low occurrence of this pathogen in sheep's bulk tank milk. In contrast, E. coliwas found in almost two-thirds of milk samples (61%) but at levels below 102CFU/mL in most of them (approximately 75%). Statistical analysis indicated that, during the warmest seasons, E. colipresence is more probable and counts are significantly higher. Unexpectedly, milk collected by hand milking had a lower level of contamination. Although further studies are necessary to clarify some aspects, the reported data add to the knowledge about the occurrence of L. monocytogenesand E. coliin raw sheep's milk and will be useful for future risk assessments.