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Incidence of pathogenic bacteria in raw milk in Ireland
Author(s) -
Rea Mary C.,
Cogan T.M.,
Tobin S.
Publication year - 1992
Publication title -
journal of applied bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.889
H-Index - 156
eISSN - 1365-2672
pISSN - 0021-8847
DOI - 10.1111/j.1365-2672.1992.tb04985.x
Subject(s) - raw milk , pathogenic bacteria , bacteria , microbiology and biotechnology , biology , incidence (geometry) , food science , mathematics , genetics , geometry
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 ≤30000/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 × 10 5 to 8.0 × 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 ≤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.