Antimicrobial sensitivity of coagulase negative Staphylococcus species isolated from bovine milk samples in Gondar and Bahir Dar area, Ethiopia
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Coagulase-negative staphylococci (CNS) are increasingly isolated from intramammary infections in bovine milk samples worldwide. In North West Ethiopia, 150 crossbreed dairy farms were sampled and a questionnaire was performed on farm and cow level factors. Out of 1523 samples, 496 samples were identified as CNS (33% of quarters). Of this sample set, 102 CNS strains were tested for antimicrobial sensitivity using disc diffusion. The strains were most resistant to penicillin (75%), tetracycline (31%) and clindamycin (23%). Cefoxitin resistance was 10%, which indicates methicillin resistance. Resistance to erythromycin and TMPS was lower with 10% and 6% respectively. 47% of strains were resistant to one or more antibiotics. Farms with a history of mastitis and treatment for mastitis in the last year had higher odds of resistance to penicillin than other farms. There was also a positive correlation between herd size and resistance. This could be because of more use of antibiotics on these farms, but that should be further analyzed together with dose and frequency of treatment. In conclusion, resistance in CNS isolated from milk samples in Gondar and Bahir Dar area is high. Adequate use of antibiotics and more studies on risk factors can help prevent further development of antimicrobial resistance.