THE OCCURRENCE OF STAPHYLOCOCCUS-AUREUS IN BULK MILK SAMPLES

In the years 1993-1994 the occurrence of Staphylococcus aureus was investigated in bulk milk samples in the area where a Baby Food Factory at Zabreh in Moravia is located, and in Bruntal, Zlin and Policka districts. Evaluation of the results was based on ECC Directive 92/46, while the dynamics of S. aureus presence was followed for the whole period of observation as well as in the particular seasons. A total of 4,485 samples was processed. Out of these, 50.7% contained less than 100 CFU/ml of S. aureus, 41.4% contained 100-500 CFU/ml, 6.73% 500-2,000 CFU/ml and 1.14% contained more than 2,000 CFU/ml (Fig. 1). The samples were divided into three categories: private new-established farms, cooperatives and State-owned enterprises in the area of the Zabreh Factory and others (Zlin, Bruntal and Policka districts). There were highly significant differences in the content of staphylococci (P = 0.01%) between the three categories of samples. Ninety-eight percent of samples from private farms, 96% samples from the Zabreh Factory area and 85% of the other samples comply with the regulation EEC 92/64 (Tab. I) for raw cow's milk for the manufacture of products ''made with raw milk'' whose manufacturing process does not involve any heat treatment (Fig. 2). The occurrence of S. aureus in the Zabreh Factory area shows an expressive seasonal dynamics (P = 0.005%) with maximum values in winter months (December-March) and minimum values in summer months (July-October) - Fig. 3. The same relationship can be seen on more extensive data files for the particular producers (Fig. 4). The issues related to culture media for S. aureus, risks of enterotoxin production and correlations with the occurrence of staphylococcus-induced mastitis in dairy cow herds are also discussed.