بررسی میزان شیوع استافیلوکوکوس اورئوس کوآگولاز مثبت در شیر دریافتی مرکز جمع آوری شیر شهرستان گرمسار

A study was carried out to estimate the prevalence of Coagulase – Positive Staphylococcus aureus in milk collected in the milk collecting center in Garmsar city. Ninety-six raw milk samples (84 composite samples and 12 bulk samples) were collected from Garmsar milk collecting center. Raw milk samples were transferred to laboratory in safe conditions. After serial dilution, the appropriate concentrations (10 -2 to 10 -6) were cultured on Baired- Parker agar medium. The plates were incubated at 37 oC for 2 days (48h). After 48 hours' incubation, the colonies with black centers and light areas were used for staphylococcal assay. The coagulase test was done with rabbit plasma and coagulate- positive colonies were then counted. The results showed that mean counts of coagulate-positive Staphylococcus aureus in composite and bulk milk were 5.4 ×10 5 cfu/ml and 3.2 × 105 cfu/ml, respectively. The counts ranged from 8.6 × 10 4 to 2.1 × 10 6 cfu/ml and 1.4 ×10 5to 5.5 × 10 5 cfu/ ml. The standard deviations were 3.5 × 10 5 cfu/ml and 1.4 × 10 5 cfu/ml respectively. It is clear that the milk collected at this facility was rather heavily contaminated with S. aureus. Therefore, it may constitute a health hazard because of the possible production of enterotoxin in the milk consumed by the people. In order to reduce staphylococcal contamination in milk, it is recommended to treat cases of clinical and subclinical staphylococcal mastitis in livestock. Also, it is necessary to use hygienic procedures during the production process as well as transportation and storage.