A total of 572 California Mastitis Test (CMT) positive milk samples were collected from 423 lactating cows on 18 private farms in the Middle Western Anatolia. Coagulase–negative staphylococci colonies and CNS species identification was performed based on conventional biochemical techniques and using the API Staph test. Slime production was detected by Congo Red Agar (CRA) method. The antibiotic susceptibility was determined according to the National Committee for Clinical Laboratory Standards guidelines (NCCLS). A total of 67 (11.7%) coagulase-negative staphylococci (CNS) were isolated from CMT positive milk samples. In total, 11 CNS species: S. epidermidis (n=18), S. simulans (n=14), S. warneri (n=10), S. hominis (n=5), S. chromogenes (n=4), S. caprae (n=4), S. xylosus (n=3), S. haemolyticus (n=3), S. hyicus (n=3), S. cohnii (n=2), and S. capitis (n=1) were identified. The most commonly identified CNS species were Staphylococcus epidermidis (26.8%) and Staphylococcus simulans (20.8%) followed by Staphylococcus warneri (14.9%). Out of 67 CNS isolates, slime production was found in 37 (55.2%) CNS strains. CNS isolates were the most resistance to trimethoprim+sulphamethoxazole (76.2%), erythromycin (73.2%), oxacillin and ampicillin (70.2%) followed by penicillin (58.3%), gentamicin (53.8%), tetracycline (52.3%), vancomycin (51.8%), ciprofloxacin (26.9%), cefoxitim (23.9%), and cephalothin (13.5%).  These results indicate that CNS species are resistant at high rates to the beta-lactam antibiotics which are intensively used in the prevention and treatment of mastitis without any antibiotic susceptibility test in the Middle Western of Turkey.

Key words: Antimicrobial susceptibility, Bovine mastitis, Coagulase negative, Slime production, Staphylococcus (CNS)