Antibiotic susceptibility of Staphylococcus aureus of bovine milk samples in Gondar and Bahir Dar region, Ethiopia

Abstract

In Ethiopia, Staphylococcus aureus (S. aureus) is an important causative agent of mastitis in dairy cows and therefore can cause significant economic losses to a community. Antibiotic resistance of S. aureus is a global problem and a threat to both veterinary and public health. The aim of this study was to estimate the prevalence of antibiotic resistance of S. aureus and to identify herd and individual cow risk factors associated with antibiotic resistance. A total of 141 isolates of S. aureus were collected from cows around Gondar and Bahir Dar with CMT positive milk, between 2014 and 2016. Samples were tested for antimicrobial sensitivity using disk diffusion with 6 types of antibiotics. The vast majority of strains showed resistance towards penicillin (94%), followed by resistance towards tetracycline (48%) and clindamycin (36%). Penicillin and tetracycline are the most used antibiotics in treatment of mastitis, which is in accordance with these results. Cefoxitin disks were used as an indicator of Methicillinresistant Staphylococcus aureus (MRSA) and were found in 6.4% of the isolates. Farmer experience in years was positively associated with clindamycin resistance, but no other risk factors were identified. A conclusive explanation of this effect is not yet found. In conclusion: a high prevalence of antibiotic resistance was seen, including MRSA in milk from Ethiopian cows, which is problematic from an animal health as well as public health perspective. Improvement in knowledge of veterinarians and farmers as well as development of national protocols regulating the use of antibiotics is important to decrease the antibiotic resistance in Ethiopia.