Prevalence, contagious pathogens and antibiotics susceptibilities of sub clinical bovine mastitis

Prevalence of bovine mastitis infection and antibiotic susceptibility profiles of 122 isolates in 11 cow herds selected from 115 herds in four districts of Chahar Mahal province in west center of Iran was studied. A total of 620 quarters milk samples from 155 lactating Holstein cows were subject to the California mastitis (CMT) test. 180 (29%) were found to be infected sub clinically. The prevalance of sub clinical mastitis in four districts was significantly higher in Lordegan than in other 3 districts. The difference between prevalence of summer (25%) and spring (34%) was not statistically significant. Of the 180 positive samples 114 coagulase positive Staphylococcus aureus (63.3%) and 8 (0.4%) Streptococcus agalactiae were identified. Microbial sensitivity of Staphylococcus aureus and Streptococcus spp was studied with 11 antibiotics currently used in therapy.