MAFF Logo Ministry of Agriculture
Fisheries
and Food
ACM/458
TABLED PAPER

Interim report from the

ADVISORY COMMITTEE ON THE MICROBIOLOGICAL SAFETY OF FOOD


NATIONAL STUDY ON THE MICROBIOLOGICAL QUALITY AND HEAT PROCESSING OF COWS' MILK

1. MAFF announced in August 1998 its intention to undertake a nation-wide survey to investigate the microbiological quality of raw and pasteurised cows' milk. The survey, part of continuing research, will take about a year to complete. Sampling commenced in March 1999.

2. Milk sampled is being examined for a range of bacteria. At the request of the ACMSF, a third of the samples are also being examined for the presence of Mycobacterium paratuberculosis. The attached information paper, which has been provided at the request of the Committee, comprises a brief summary of M. paratuberculosis results to date.

3. A review of the evidence for and against a possible link between M. paratuberculosis and Crohn's Disease was first considered by the Advisory Committee on Dangerous Pathogens (ACDP) in 1992 when they concluded that a link could not be established on the available evidence. ACDP studied the situation again in 1998 and confirmed its earlier view that a link between M. paratuberculosis and Crohn's Disease could not be demonstrated on the basis of current evidence.

4. The ACMSF has considered M. paratuberculosis on a number of occasions over the period 1995-98. The Committee concluded that, although there was as yet no evidence of a public health problem, it would nevertheless be prudent to maintain a cautious approach. The Committee has consistently supported MAFF's research and surveillance effort with regard to this organism.

5. The Department of Health advice remains that, on the basis of what is currently known about M. paratuberculosis, there is no need for anyone to change their dietary habits.

Secretariat
December 1999


ADVISORY COMMITTEE ON THE MICROBIOLOGICAL SAFETY OF FOOD

INFORMATION PAPER:

NATIONAL STUDY ON THE MICROBIOLOGICAL QUALITY AND HEAT PROCESSING OF COWS' MILK

Background

1. The National Study on the Microbiological Quality and Heat Processing of Cows' Milk comprises a representative sample of approved dairy establishments throughout the UK which heat treat milk (both drinking milk and milk for the manufacture of milk products). In addition to microbiological examination of samples of milk before and after heat processing, details of the quality management systems and process controls are being collected. Sampling for the survey began in March 1999 and will continue for approximately 12 months.

3. At each sampling visit, one raw and a number of pasteurised milk samples (whole/semi-skimmed/skimmed) are collected and examined for a range of microorganisms. Wherever possible, the raw and pasteurised milk samples originate from the same batch of milk.

4. Approximately 1000 samples (a third of the total) are being examined for the presence of Mycobacterium paratuberculosis. The methodology comprises a rapid screen, using immunomagnetic separation coupled to PCR, in conjunction with conventional decontamination and culture to confirm viability. When acid-fast cells are observed, further confirmatory tests are carried out. An acid-fast isolate will be considered to be viable M. paratuberculosis only if it meets all of the following criteria:

Results

5. To date, 431 samples of raw or pasteurised milk have been examined for the presence of M. paratuberculosis. Due to the very slow growth rate of this bacteria, most results are still pending but confirmed results are available for 192 samples.

Number of confirmed M. paratuberculosis results
  Positive Negative
Raw milk 3 56
Pasteurised milk 4 129
Total 7 185

6. Viable M. paratuberculosis has been found in about 5% of the raw milk samples and about 3% of the pasteurised milk samples for which confirmed results are available. In respect of the pasteurised milk samples, there was no indication from either the phosphatase testing or other microbiological examinations that the milk had not been correctly pasteurised.

Food Hygiene Division
November 1999