Determining a pathogen’s spectrum of resistance to antimicrobials is often a critical component in successfully treating bacterial infections. Hence, a cross-sectional study was carried out from November 2013 to May 2014 to determine antimicrobial susceptibility patterns of bacterial pathogens isolated from bovine mastitis in smallholder dairy farms in Sinana district, Bale Zone, South Eastern Ethiopia. Bacteriological methods and antimicrobial sensitivity tests were employed. The most prevalent culture growth was Staphylococcus aureus (33.24%) followed by Streptococcus agalactiae (22.25%), Staphylococcus epidermidis (9.34%), Escherichia coli (7.42%), Coagulase Negative Staphylococci (CNS)(7.14%), Streptococcus dysgalactiae (5.77%), Corynebacterium bovis (4.40%), Streptococcus uberis (3.85%), Klebsella pneumoniae (2.75%), Pseudomonas aeruginosa (2.2%) and Bacillus cereus (1.65%). Most of the isolated bacterial pathogens were sensitive to Chloramphenicol (95.2%) followed by Ciprofloxacin (92.1%), Gentamycin (88.1%), Clindamycin (87.9%) and Vancomycin (85.2%).Whereas, the highest rate of resistance among the isolates was against Penicillin (66%), Tetracycline (60%), Ampicillin (56.2%) and Trimethoprim /sulfamethoxazole (54.7%). The results of the present study suggests that the higher frequency of resistant bacterial isolates were recorded for poor teat hygiene; previous mastitis record and aged cows than their counter parts. The present study revealed risk of an emergence of an antimicrobial resistance among mastitis bacterial pathogens in and around Sinana district. This implicates the importance of the choice and appropriate use of antimicrobial agents to use prudently in dairy farms. Regular antimicrobial sensitivity testing and recognizing the appropriate pattern of antibacterial susceptibility could help to choice appropriate antibiotics and prevent resistance to newly developed antibiograms.

Keywords: Antimicrobial, susceptibility, bacterial pathogens, bovine mastitis, Bale Zone.