title: Incidence and seasonal variation of Listeria species in bulk tank goat's milk.
abstract: Four hundred and fifty raw goat's milk samples obtained from the bulk tanks of 39 goat farms were analyzed for Listeria spp. over a 1-year period. Modified versions of the U.S. Department of Agriculture Food Safety and Inspection Service (USDA-FSIS) and Food and Drug Administration (FDA) protocols were used for recovery of Listeria. Overall, 35 (7.8%) samples yielded Listeria spp. with Listeria monocytogenes identified in 17 of the 35 (3.8%) Listeria-positive samples. Listeria innocua was detected in 26 (5.8%) samples. Eight milk samples contained both L. monocytogenes and L. innocua. Milk samples from 18 of the 39 (46.2%) farms were positive for Listeria at least once during this 1-year study. The modified USDA-FSIS method, which used Listeria repair broth rather than University of Vermont (UVM) broth for primary enrichment followed by a 4-h nonselective incubation period, yielded more Listeria-positive samples (77.1%) than the FDA method (51.4%). All L. monocytogenes isolates belonged to serotypes 1 (62.6%) or 4 (37.4%). Moreover, five different Listeria ribotypes were identified from 34 selected L. monocytogenes isolates, 2 of which were deemed to be of clinical importance. Listeria isolation rates were markedly higher during winter (14.3%) and spring (10.4%) as compared to autumn (5.3%) and summer (0.9%) with these trends similar to those previously reported for cow's milk.
authors.affiliation: Department of Nutrition and Food Sciences, University of Vermont, Burlington 05405, USA.
authors.forename: A A
authors.initials: AA
authors.lastname: Abou-Eleinin
authors.forename: E T
authors.initials: ET
authors.lastname: Ryser
authors.forename: C W
authors.initials: CW
authors.lastname: Donnelly
mesh_terms: D000818:Animals; D003470:Culture Media / Q000737:chemistry; D006041:Goats; D015994:Incidence; D008087:Listeria / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D008089:Listeria monocytogenes / Q000145:classification / Q000235:genetics / Q000302:isolation & purification; D008892:Milk / Q000382:microbiology*; D021521:Ribotyping; D012621:Seasons; D012703:Serotyping
chemical_list: D003470:Culture Media