INCIDENCE OF PATHOGENIC BACTERIA IN RAW-MILK IN IRELAND

Raw milk from 70 farms was sampled over 13 months for salmonellas, listerias, Escherichia coli, Staphylococcus aureus and mastitic streptococci; total bacterial counts (TBC), coliforms and somatic cells were also counted. TBC less-than-or-equal-to 30 000/ml were obtained in 63 % of samples. High count milks were found mainly during the winter months: 13 % of samples had > 10(4) mastitis pathogens/ml of milk. The mean somatic cell count varied from 4.0 x 10(5) to 8.0 x 10(5)/ml throughout the year with highest counts during the late lactation period. Coliforms were present in all samples, but 65-71 % of samples had < 100 coliforms/ml. Up to 60 % of supplies had less-than-or-equal-to 10 E. coli/ml. One of the 589 samples tested (0.1 %) was positive for salmonellas. Yersinia enterocolitica and Y. enterocolitica-like organisms were isolated from 39 % of samples with up to 68 % of samples positive at some sampling periods. A total of 222 strains of yersinias were isolated; Y. enterocolitica (59 %) was the most common strain followed by Y. fredriksenii (35 %), Y. kristensenii (1.0 %), Y. intermedia (4.5 %) and Y. aldovae (0.5 %). Listerias were isolated from 8.3 % of samples tested; 4.9 % were Listeria monocytogenes and 3.4 % were L. innocua. There was a significant rise in the isolation rate between December and April from a base line of 0-5% during the spring and summer to 35-37 % during the winter months while the cows were indoors. Of 66 silage samples tested from the farms involved in the survey 9 % of samples were positive for listerias; 3 % of these were L. monocytogenes and 6 % were L. innocua. Only half of the farms feeding contaminated silage produced milk containing listerias.