Isolation and antimicrobial resistance patterns of Methicillin-resistant Staphylococcus aureus from raw cow's milk in dairy farms of Wolaita Sodo Town, Southwest, Ethiopia

Abstract

Staphylococcus aureus is a pathogenic bacterium-contaminating milk and milk products causing food poisoning primarily due to its enterotoxins. A cross-sectional study was conducted from November 2021 to June 2022 in Wolaita Sodo Town, to detect Methicillin-resistant Staphylococcus aureus (MRSA) in raw cow's milk and assess their resistance levels to different antimicrobials. Purposive sampling was used to select 34 dairy farms. Accordingly, 419 raw milk samples from the farm and collection centers were collected. Isolates of S. aureus showing resistance to Cefoxitin were classified as MRSA. From the total 419 samples, 22.19% (93/419) were contaminated with S. aureus in dairy cows. The prevalence of S. aureus in raw milk, bulk milk from the farm, and bulk tank milk from the collection centers was 16.9%, 2.1%, and 3.1%, respectively. The risk of S. aureus contamination in dairy farm owners and milkers who do not take food safety training was 5.303 times higher than the risk of S. aureus contamination in dairy farm owners and milkers who take food safety training. The risk of S. aureus contamination in dairy farms kept under poor management system was 7.34 times more than that of dairy farms kept under good management. The cefoxitin disk diffusion method was used to detect MRSA, 57.14% being resistant to Cefoxitin in total while approximately 87.5% were sensitive to Sulfamethoxazole-trimethoprim and Gentamycin, while Erythromycin registered 75%, Ciprofloxacin 62.5%, Chloramphenicol 62.5%, and Tetracycline 25%. This study revealed that MRSA exhibited a notable multidrug resistance pattern, encompassing resistance to multiple drugs, with a prevalence of 75%. Significantly, the hands of milkers and the milking containers emerged as pivotal sources of contamination. This underscores the crucial importance of maintaining stringent hygienic practices during the milking process, with particular emphasis on thorough cleaning and decontamination of utensils.