Mamo, Gezahegne (PhD)Ketema, Abinet2018-06-272023-11-082018-06-272023-11-082015-06http://etd.aau.edu.et/handle/123456789/3912Among the animal diseases that require antibiotic treatment in dairy herds, mastitis is the commonest one. Mastitis pathogens like Staphylococcus aureus have received recent attention due to antimicrobial resistance potential. A cross-sectional study was carried out from, November 2014 to may 2015 to determine the prevalence and phenotypic characteristics of Methicillin Resistant Staphylococcus aureus (MRSA) isolated from mastitis lactating dairy cattle in and around Batu, Ethiopia. A total of 216 lactating cows were examined clinically as well as by California mastitis test (CMT) to detect clinical and sub clinical mastitis. Of the total dairy cattle examined, 92 (42.59%) were found to be positively reactive to CMT. From the total count, the clinical and subclinical mastitis forms were 6.48% (14/216) and 36.11% (78/216) respectively. Among the total 864 quarter examined, 12(1.39%) quarters were found blind and overall prevalence of mastitis 172(19.9%) at quarter level was recorded. From the total infected quarter, the front and hind quarter share 68(7.87%) and 104(12.03%) respectively. The collected milk samples (California Mastitis Test Screened) were cultured on sheep blood agar and confirmed by other biochemical tests commonly used for Staphylococcus aureus identification. For all except breed and floor type, the multivariable logistic regression analysis for intrinsic and extrinsic risk factors showed significant value for the prevalence of mastitis in the study area (P˂0.05). Productions of biofilm on the isolates were evaluated on Modified Congo Red Agar (MCRA) and only red colonies detected, indicating a bacterium without biofilm production. Pure S. aureus isolates were subjected to antimicrobial susceptibility test and 12(32.43%) MRSA have been identified from a total of 37 S. aureus using cefoxitin through disk diffusion method. The isolates were found highly sensitive to Kanamycin 35 (94.6%), however they were least sensitive to Amoxicilin 9(24.3%). In the present study the Multiple Antibiotic Resistance Index analyses revealed that an existence of isolates originated from an environment where several antibiotics are used MAR Index > 0.2. Generally, the study showed that mastitis is an important problem and a potential growing of MRSA will be serious threat for dairy industry in the study area. Therefore, there is a need for building specific measures to tackle the problem and antimicrobial sensitivity testing should be implemented more often. Key word: Biofilm, Cefoxitin, dairy cattle, Mastitis, MRSA, risk factors, Staphylococcus aureusenBiofilmCefoxitindairy cattleMastitisMRSrisk factors, Staphylococcus aureuThesis