With the view of clarifying sources and routes of contamination of foods with
L. monocytogenes, an actual survey was made of cow and pig carriers brought to the Tokyo Metropolitan Shibaura Abattoir and of the contamination of carcases in the course of the meat processing. The rate of detection of
L. monocytogenes from bovine intestinal contents was 2.3% compared with 0% for pigs. The rate of contamination of carcases with
L. monocytogenes was 6.7-10.0% for cows and 1.7-30.0% for pigs, depending upon the stages of the processing; it was highest for swine carcases brought in from other abattoirs. Meat processing utensils such as knives and chopping-boards as well as employee's fingers showed a rate of detection of 14.3-31.0%, suggesting their responsibilities for the contamination of the meat.
On the other hand, it was revealed that bovine carcases stored at-1-0°C for one day had more than a 50% reduction rate in the detection of
L. monocytogenes.
In this survey,
L. monocytogenes isolated from bovine intestinal contents and carcases, swine carcases and meat processing utensils was classified into 7 serotypes, including 4b and 1/2b, which have frequently been isolated from patients with listeriosis.
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