Identification and Determination of Antibiotic Resistance Pattern of Bacterial Agents that Causes Bovine Clinical Mastitis in Tabriz

Mastitis is the costliest disease threatening the cattle breeding industry. This study was designed to identify the bacterial agents that causes clinical mastitis and antibiotic susceptibility of isolates in dairy cattle in   agro industrial complexes in Tabriz, Iran. In this study, 234 milk samples were collected from cows with clinical mastitis. The isolates were identified by standard microbiological methods. Antibiotic susceptibility of isolated were performed by disc diffusion method using antibiotic discs, frequently used in veterinary medicine in the region.   The most isolated bacteria were Escherichia coli with (18/8%) of isolates, flowed by Coagulase positive staphylococci (17/9%), Coagulase negative staphylococci (12/8%), Bacillus species (11/9%), respectively. No bacterial agent was isolated from 80 samples. The Escherichia coli isolates had the highest susceptibility to Gentamicin (90%) and the lowest sensitivity to Penicillin (0%). This result was also true for isolates of Staphylococcus coagulase negative and isolated bacilli. Cotrirmaxazole was the most effective (80. 95%) and penicillin-less effective against coagulase-positive staphylococci. Gentamicin was found to be more effective antibiotic among all the tested antibiotics. The least sensitive antibiotic was Penicillin   with 1/23% sensitivity. Coagulase negative staphylococcus was only sensitive group of isolates to penicillin. Escherichia coli and Staphylococcus aureus showed the most role in mastitis in this study.  Resistance to antibiotics was observed in all isolates. Gentamicin with 83.95% sensitivity was the most effective and penicillin with 1/23% sensitivity was the least effective antibiotics. Antibiogram and choosing the correct antibiotic before treatment will have a great effect on reducing microbial resistance in mastitis.