Epidemiological investigation and antimicrobial sensitivity of Staphylococcus aureus in dairy farms of selected towns in Western oromia, Ethiopia.

The aim of this study is to estimate prevalence, investigate potential risk factors and determine the antimicrobial sensitivity of Staphylococcus aureus in dairy farms of purposively selected towns in western Oromia: Bako, Nekemte and Gimbi. A cross-sectional study was conducted from November 2020 to June 2021. A total of 347 samples consisting of 255 raw milk, 49 milkers' hand swab and 43 milking bucket swabs were collected and examined for Staphylococcus aureus using bacteriological culture and biochemical tests. Dairy animals were selected by simple random sampling. Risk factors for the occurrence of Staphylococcus aureus in dairy farms were assessed through interviews and personal observation. The isolates were tested for drug sensitivity using disk diffusion techniques. The overall prevalence of S. aureus was 18.44% (95% CI: 14.69-22.90). The proportion of isolation was 17.25% (95% CI: 13.07-22.43), 30.61% (95% CI: 19.03-45.29) and 11.63% (95% CI: 4.74-25.79) from raw milk, swabs of milkers' hand and milking bucket, respectively showing insignificant difference (P < 0.05). Prevalence of Staphylococcus aureus within the breed, parity, lactation stage, hand washing at the milking interval and hygiene of the barn were also significant. The Antimicrobial test showed the highest susceptibility to ciprofloxacin (100%), gentamicin (90%), vancomycin (85%) and chloramphenicol (85%) but the highest resistance to penicillin G (85%), ampicillin (75%) and tetracycline (50%). None of the isolates showed multidrug resistance. Such Staphylococcus aureus prevalence with also the antibiotic resistant isolates suggests a public health risk thus the need to address this issue to protect both human and animal health.