Detection of presumptiveBacillus cereusin the Irish dairy farm environment

• Published in: Irish journal of agricultural and food research Vol. 55; no. 2; pp. 145 - 151
• Main Authors: O'Connell, A., Lawton, E.M., Leong, D., Cotter, P., Gleeson, D., Guinane, C.M.
• Format: Journal Article
• Language: English
• Published: Teagasc 01.01.2016
• Subjects: Agrology; Bacillus cereus; Grasses; Milk; Milking; Sequencing; Soil pollution; Soil samples; Tap water; Water samples
• ISSN: 0791-6833; 2009-9029

The objective of the study was to isolate potentialBacillus cereussensu lato (B. cereus s.l.) from a range of farm environments. Samples of tap water, milking equipment rinse water, milk sediment filter, grass, soil and bulk tank milk were collected from 63 farms. In addition, milk liners were swabbed at the start and the end of milking, and swabs were taken from cows' teats prior to milking. The samples were plated on mannitol egg yolk polymyxin agar (MYP) and presumptiveB. cereus s.l.colonies were isolated and stored in nutrient broth with 20% glycerol and frozen at –80 °C. These isolates were then plated on chromogenic medium (BACARA) and colonies identified as presumptiveB. cereus s.l.on this medium were subjected to 16S ribosomal RNA (rRNA) sequencing. Of the 507 isolates presumed to beB. cereus s.l.on the basis of growth on MYP, only 177 showed growth typical ofB. cereus s.l.on BACARA agar. The use of 16S rRNA sequencing to identify isolates that grew on BACARA confirmed that the majority of isolates belonged toB. cereus s.l.A total of 81 of the 98 isolates sequenced were tentatively identified as presumptiveB. cereus s.l.Pulsed-field gel electrophoresis was carried out on milk and soil isolates from seven farms that were identified as having presumptiveB. cereus s.l.No pulsotype was shared by isolates from soil and milk on the same farm. PresumptiveB. cereus s.l.was widely distributed within the dairy farm environment.