Prevalence and antibiogram of Staphylococcus aureus isolates in bovine raw milk from small-scale farmers in Magu district, Mwanza, Tanzania.

Abstract

BACKGROUND: Staphylococcus aureus, a common cause of foodborne illnesses, may be transmitted from cows to humans through contaminated raw milk. Limited data exist on livestock-associated Staphylococcus aureus (LA-S. aureus) infections in Tanzania's bovine supply chain. This study assessed the prevalence and antibiogram of Staphylococcus aureus in cows' raw milk, from small-scale farmers in Magu district, Mwanza, Tanzania. METHODS: A cross-sectional study was conducted between April 2023 and June 2024. A total of 410 non-repetitive raw milk samples were collected from cows of small-scale farmers. Milk samples were processed to isolate Staphylococcus aureus as per laboratory standard procedures. Drug susceptibility was established with the Kirby-Bauer disk diffusion method following the Clinical and Laboratory Standards Institute (CLSI) guidelines, 2022. R software was used to analyze percentages and proportions of the data for all variables. RESULTS: The prevalence of Staphylococcus aureus in raw milk from small-scale farmers was 23.9% (98/410), with 16.3% (16/98) being methicillin-resistant Staphylococcus aureus (MRSA). The resistance proportions were penicillin 45.9% (45/98), tetracycline 33.7% (33/98), erythromycin 21.4% (21/98), cefoxitin 16.3% (16/98), clindamycin 6.1% (6/98), trimethoprim-sulfamethoxazole 6.1% (6/98), gentamicin 3.1% (3/98), and ciprofloxacin 1.0% (1/98). Of the 98 Staphylococcus aureus isolates, 20 (20.4%) were multidrug resistant (MDR) defined as resistance to three or more antibiotics. CONCLUSION: The prevalence of Staphylococcus aureus was high with a significant proportion of isolates being MRSA, in raw milk from small-scale farmers. High proportions of antibiotic resistance and MDR patterns underscore the urgent need for improved antimicrobial stewardship and the promotion of responsible antibiotic use in dairy farming.