A total of 102 smallholder dairy farms and 303 cross bred milking cows were examined to determine the overall prevalence of mastitis, to identify risk factor, to isolate and identify bacterial pathogens and to conduct in vitro antimicrobial susceptibility test in Adama Town, Ethiopia using pre-tested questionnaires, California mastitis test (CMT), microbial isolation and identification and in vitro antibiotic susceptibility test. The overall mastitis prevalence was 73.4% (at herd), 39.5% (at cow) and 23.7% (at quarter) level of which (15.6 and 57.8%) at herd, (5.9 and 33.6%) at cow and (2.9 and 20.8%) at quarter level were clinical and sub-clinical mastitis respectively. The major isolates of subclinical mastitis cases were Staphylococcus aureus (26.8%), Staphylococcus intermedius (2.5%), Coagulase Negative Staphylococcus (CNS, 18.7%),Streptococcus agalactiae (5.8%), Streptococcus dysgalactiae (2.0%), Streptococcus uberis (4.5%) and Escherichia coli (6.5%) and from clinical mastitis were S. aureus(2.5%) and S. agalactiae (3.8%). Among the risk factors stage of lactation, parity and presence of teat lesions have been shown statistically significant (p<0.05) difference in the prevalence of mastitis. In the present study, out of the nine in vitro antimicrobials used, Gentamycine (3.1%), Chloramphinicol (4.2%), Vancomycin (17.6%), Streptomycin (25.4%), Kanamaycin (26.4%), Polymyxin B (48.6%), Penicillin (48.9%), Amoxicillin (68.7%) and Bacitracin (74.9%) showed resistance to mastitic pathogens. Gentamycine and Chloramphinicol were found to be more effective antibiotic among all the tested antibiotics. The main reasons for the occurrence of a high number of resistant strains in this study were the use of sub-therapeutic level of antibiotics and/or short treatment episodes and the long-term presence of infected cows in herds.Finally, due to the high resistance levels detected in the present study, it was believed that it is necessary to set up antimicrobial resistance (AMR) surveillance programs in the country.
Key words: Mastitis, bacteria, isolates, antibiotic, susceptibility, prevalence, risk factors.
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