ENVIRONMENTAL SURVEILLANCE OF DAIRY PROCESSING PLANTS FOR THE PRESENCE OF YERSINIA SPECIES

Thirty dairy processing plants were surveyed to determine if the psych rotrophic nature of Yersinia influenced its environmental niche within the plants. Three hundred forty-seven samples obtained from 30 dairy processing plants were tested for the presence of Yersinia spp. Ten (3 3.3%) plants had one or more positive sites. A total of 20 of the 347 (5.8%) sites tested were positive for one or more species of Yersinia. Yersinia enterocolitica was present at 85% (17/20) of the positive si tes. It was identified by itself on 15 occasions and twice with other species of Yersinia. Other species identified included Yersinia rucker i in 3 of the 20 positive samples (15%); Yersinia kristensenii and Yer sinia frederiksenii both in 1 of the 20 (5%) positive samples. Ten of the 20 (50%) positive samples were obtained from coolers and entrances to freezers. Yersinia-positive cooler/freezer sites were obtained fro m 9 of the 10 positive plants. The remaining 10 Yersinia - positive si tes were from raw milk receiving areas (4/10) and drains around machin ery (6/10), including an ice maker, a case washer, two holding tanks, one filler machine and a packaging area. These results reinforce both the psychrotrophic nature of Yersinia and the evidence that raw milk c an be a primary source of the organism. Our findings show that sanitat ion schemes need to be developed for coolers and freezers to prohibit the colonization and proliferation of Yersinia within these areas.