Isolation, identification and antimicrobial susceptibility pattern of Salmonella, E. coli, and S. aureus from selected dairy farms in Bedele and Nekemte Districts, Western Ethiopia

Abstract

Background: Bacterial diseases transmitted through food pose a serious threat to human and animal health. Salmonella, E. coli, and S. aureus are among the major foodborne pathogens. It is becoming a worldwide problem to date. In this regard, there is a lack of information among farms in western Ethiopia. Therefore, the study was conducted to isolate, identify, and assess the antimicrobial susceptibility profile of Salmonella, E. coli, and S. aureus from selected dairy farms in the study area. Methodology: A cross-sectional study was done from December 2018 to June 2019 on small-scale dairy farms from Bedele and Nekemte town, Western Ethiopia with the objective of isolating and identifying Salmonella, E. coli, and S. aureus from lactating cows, milkers’ and milking equipment at farms and to determine the antimicrobial susceptibility of the isolates. A total of 383 samples consisting of cow milk, feces, cow nasal swabs, milkers’ hand swabs, milkers nasal swabs, bucket swabs, and floor swabs were collected from 20 dairy farms. The samples were examined for the presence of Salmonella, E. coli, and S. aureus following standard techniques and procedures. The agar disc diffusion method was used for the antimicrobial susceptibility testing. Results: The overall occurrence of Salmonella, E. coli, and S. aureus was 2.35%, 11.75%, and 2.35% respectively. Out of the 9 Salmonella isolates, 5(4.95%), 3(2.97%), and 1(5%) were isolated from udder milk, rectal feces, and floor swab respectively. S. aureus isolate was highest in udder milk 3(2.97%), followed by cow nasal swab 2(1.98%), feces 1(0.99%), bucket swab 1(5%), floor swab 1(5%) and milker’s nasal swab 1(5%). E. coli was highest in milk sample 19(18.81%), followed by fecal samples 16(15.84%), bucket swab 5(25%), floor Swab 4(20%) and 1(0.99%) in cow nasal swab. All Salmonella isolates were 100% sensitive to nalidixic acid, however 55.55%, 22.22%, and 11.11, respectively, were resistant to cefoxitin, tetracycline, and gentamycin. Tetracycline, cefoxitin, and streptomycin resistance were observed in 33.33%, 9.52%, and 19.05% of E. coli isolates, respectively. On the other hand, all isolates were 100% sensitive to nitrofurantoin, ceftriaxone, nalidixic acid, and ciprofloxacin. The antibiotic susceptibility profiles of S. aureus showed that 55.55% and 11.11% were resistant to Penicillin G and Erythromycin, respectively and all isolates were 100% sensitive to cefoxitin, nitrofurantoin, and gentamicin. Conclusion: The current study shows lower prevalence, lower antimicrobial resistance, and higher susceptibility for most antimicrobials. Recommendation: Stringent control measures, such as treatment of positive cases with effective medications and preventative measures including strict hygiene standards, such as cleaning of the floor, pens, and milking equipment, as well as adequate hand washing throughout the milking process, should be adopted.