Isolation of Listeria species from farm bulk milk at the receiving dairy plant and cervico-vaginal swabs
Abstract
Listeria species were isolated from farm bulk milk (n=123) at the receiving dairy plant and cervico-vaginal samples (n=20) collected from dairy cows with reproductive disorders. Following enrichment and plating on two selective agar media, confirmation of the isolates was based on standard tests. Isolates were subjected to a PCR assay for detection of the hlyA gene. Overall, Listeria spp. were isolated from 30(24.4%) bulk milk samples and four (20%) cervico-vaginal swabs. Listeria monocytogenes was isolated from 17.9%, L. innocua from 1.6%, L. seeligeri from 3.3% and L. welshimeri from 1.6% bulk milk samples. Only L. monocytogenes (10%) and L. innocua (10%) could be isolated from cervico-vaginal swabs. The hlyA gene was detected in all L. monocytogenes isolates. These findings represent a public health risk where homemade unpasteurised milk and milk products are largely consumed.
