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Persistence of Mycobacterium bovis and Verocytotoxin-producing Escherichia coli (VTEC) in UK-Made Raw Milk Cheeses

Institutions
Campden BRI
Queen's University - Belfast
Start date
2007
End date
2011
Objective

Different types of cheese made from unpasteurised milk were taken to be representative of, for example, a hard and a soft cheese. These products differed in their characteristics with respect to the environment they present to M.bovis or any other microorganism found to be present (e.g VTEC). Information on values for characteristics such as salt and pH came from the expertise in the team carrying out the study, but measurements were also made.

Methods for detecting, isolating and calculating both M.bovis and VTEC O157:H7 from milk and cheeses were developed and evaluated in this study. The ability to detect and isolate non-O157 VTEC (e.g. O26, etc.) from cheeses was also investigated.

Cheeses were manufactured in the laboratory and inoculated separately with both species of bacteria. The microflora and characteristics of the cheeses were monitored throughout the life of the cheeses, so that the impact on the growth and survivability of M.bovis and VTEC could be evaluated effectively. This enabled the safety of raw milk cheeses to be assessed more precisely.

The project team consisted of experts in the areas of M.bovis, VTEC and cheese and were supported by a steering group comprising cheese manufacturers and other experts in cheese production.

More information

Background: Research has shown that there is a potential for Mycobacterium bovis (M.bovis) to survive in cheeses made from unpasteurised milk. A great deal is known about the survival of Verocytotoxin-producing E.coli (VTEC) O157:H7 in some foods. However, not a lot is known about it in fermented dairy foods such as cheese, where starter cultures and naturally occurring microorganisms may compete with this pathogen.

This project investigated the survivability of M.bovis and relevant VTEC serotypes, such as O157:H7, through the manufacture of raw milk cheeses which are made in the UK. Benchmark cheeses were identified for use in the project. These were then inoculated with these key pathogens. Outcomes from the project enabled the safety of raw milk cheeses to be assessed.

Funding Source
Food Standards Agency
Project source
View this project
Project number
FS231037(B12008)
Categories
Escherichia coli
Bacterial Pathogens
Commodities
Dairy