Analysis of protein A gene polymorphism in Staphylococcus aureus isolates from bovine mastitis

One hundred and three isolates of Staphylococcus aureus from bovine mastitis were investigated by PCR for gene polymorphism in the X region of the protein A. On the basis of the size of corresponding PCR products (100-320 bp), 2-11 repeats were supposed to be present in the genes investigated. The isolates showed 8, 9, 10 and 11 repeats most frequently (20.39%, 15.53%, 14.56% and 16.50%, respectively). Seven or less repeats were found only in 33% of the isolates. Somatic cell count in milk samples from quarters infected with strains which harboured more than 7 repeats was significantly higher than from quarters infected with strains which harboured 7 or less repeats (6 244 +/- 7 829 x 10(3)/ml vs. 2 803 +/- 2 415 x 10(3)/ml).