Study of antibiotic susceptibility of Coagulase- Negative staphylococci isolated from bovine mastitis

A total of 141 milk samples were tested belong to 27 cows infected with clinical mastitis and 114 cows were diagnosed with subclinical mastitis after detected their milk samples by California Mastitis and Whiteside tests, samples were collected from different areas of Mosul city. After the first isolation, the biochemical tests were carried out on all isolation. The samples showed 33 (23.40%) isolates of Coagulase-Negative Staphylococci (C-NS). S. chromogenes & S. epidermidis were predominant in clinical mastitis, while in the sub-clinical cases the S. haemolyticus was most frequently in isolation. The sensitivity test was carried out on isolated bacteria. The test results showed that there was absolute resistance to ampicillin and 90.9% for Penicillin-G, while the lowest resistance and highest sensitivity of Chloramphenicol was 27.27%, 57.57%, respectively, as well as, isolated give varying sensitivity and resistance to other antibiotics. The use of antibiotics at random and the non-completion of treatment the animal by the owner lead to produce a normal flora resistant to most common veterinary antibiotics used, which can become a pathogen when conditions are available, this shown by the results of the current study.