Use of plasmid profiles and restriction endonuclease digest in environmental studies of Listeria spp. from raw milk.
Forty-eight isolates of Listeria spp. (19 L. monocytogenes, 27 L. innocua, 2 L. welshimeri) from bulk raw milk were screened for plasmid DNA. These isolates were collected over a period of 1 year. Only L. innocua harboured plasmids (8/27 strains) which ranged in size 10-44 megadaltons. The plasmid bearing strains could be arranged into three groups 10 Md, 44 Md and 44 + 10 Md. In two farms where Listeria innocua were persistent in bulk raw milk different plasmids profiles were found (farm 1 and 3). In species carrying similar plasmid profiles (44 Md) isolated from the same bulk tank raw milk samples over a period of 2-4 months (farm 2) no similarities in restriction endonuclease digest patterns of the plasmids were observed. This study suggests there may be a constant influx of Listeria spp. into raw milk supplies on the farm.
Fistrovici
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Department of Environmental Biology, University of Guelph, Ontario, Canada.
Collins-Thompson
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D000818:Animals; D004269:DNA, Bacterial / Q000032:analysis*; D005516:Food Microbiology; D008087:Listeria / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification; D008089:Listeria monocytogenes / Q000145:classification / Q000235:genetics / Q000302:isolation & purification; D008892:Milk / Q000382:microbiology*; D010957:Plasmids; D015183:Restriction Mapping
D004269:DNA, Bacterial