evaluation of protein a gene tandem repeat polymorphism of staphylococcus aureus isolated from bovine mastitis in tabriz

results a number of 7-11 repeats in the spa gene xr region were determined. strains with 10 repeats were65%, therefore they had the highest percentage in isolates. seven repeats strains were 20% and each of the strains with 8, 9 and 11 repeats had the frequency of 5%. s. aureus strains antibiotic resistance was 35%, 5%, 45% and 40% for tetracycline, amoxicillin, gentamicin and erythromycin respectively. all strains were susceptible to methicillin and vancomycin. objectives staphylococcal protein a (spa) is one of the virulence factors of s. aureus which were encoded by spa gene. different strains of s. aureus are varying in dissemination ability and power to infect mammary glands. the spa gene region xr polymorphic sequence can be used for typing. materials and methods twenty s. aureus cultures were isolated from bovine raw milk and analyzed for the number of repeats in region xr of the spa gene by pcr. background staphylococcus aureus is responsible for about one third of mastitis cases in dairy cattle and it is also the main pathogen of contagious mastitis. conclusions results of the current study indicated that 80% of strains had more than 7 repeats in the xr region of the spa gene and these data were consistent with the previous findings. significance and impact of the study: evaluation of spa gene polymorphism can be useful in epidemiological studies on s. aureus distribution and its control.