Browsing Food Programme by Subject "Bacillus cereus"
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Detection of presumptive Bacillus cereus in the Irish dairy farm environmentThe objective of the study was to isolate potential Bacillus cereus sensu 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 presumptive B. 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 presumptive B. cereus s.l. on this medium were subjected to 16S ribosomal RNA (rRNA) sequencing. Of the 507 isolates presumed to be B. cereus s.l. on the basis of growth on MYP, only 177 showed growth typical of B. 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 to B. cereus s.l. A total of 81 of the 98 isolates sequenced were tentatively identified as presumptive B. cereus s.l. Pulsed-field gel electrophoresis was carried out on milk and soil isolates from seven farms that were identified as having presumptive B. cereus s.l. No pulsotype was shared by isolates from soil and milk on the same farm. Presumptive B. cereus s.l. was widely distributed within the dairy farm environment.
The microbiological safety and quality of foods processed by the "sous vide" system as a method of commercial cateringThe objective of this project was to improve the quality and safety of sous vide foods by investigating the responses of the food-poisoning microorganisms to the processing and storage conditions used in this technology. The major food poisoning bacteria of concern in sous vide foods are strains of Clostridium botulinum, Bacillus cereus, verotoxigenic Escherichia coli O157:H7 (VTEC), Salmonella spp., Listeria monocytogenes and Yersinia enterocolitica.
Occurrence and identification of spore-forming bacteria in skim-milk powdersThe different customer and regulatory specifications for mesophilic and thermophilic aerobic and anaerobic spore numbers in skim-milk powder, in addition to some specifications on specific spore-forming bacteria, such as Bacillus cereus, can be challenging for the industry to meet. Twenty-two samples of medium-heat skim-milk spray-dried powder from eight sources were analysed in triplicate with 16 bacterial and spore enumeration tests to understand the variety of spore-forming bacteria population. Using 16S rDNA sequencing, the species were identified for 269 isolates that were representative of the various tests. Of the isolates identified, 68% were Bacillus licheniformis, a facultative anaerobe that can survive and grow at mesophilic and thermophilic temperatures, making it difficult to eliminate in manufacturing environments. Using whole genome sequencing, 16 of 23 isolates identified as B. licheniformis by 16S sequencing were confirmed as B. licheniformis, four were identified as Bacillus paralicheniformis and three were identified as Bacillus sp. H15-1.
Review of potential sources and control of thermoduric bacteria in bulk-tank milkBacteria that contaminate milk include thermoduric bacteria that can survive pasteurisation and subsequently grow in the pasteurised milk or contaminate product. Elimination of thermodurics at milking is not feasible. Therefore, knowledge of their source and strategies for their reduction are important. The major sources of thermodurics in milk are contamination of the teat skin from soil and bedding, and subsequent contamination from deposits that can build up on milking equipment surfaces. Hygiene at milking can reduce the number of bacteria contaminating milk. Teat preparation at milking and a recommended plant cleaning procedure are critical to the prevention of the contamination of milk with thermoduric bacteria.