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

TL;DR

This study found high rates of Staphylococcus aureus, including drug-resistant strains, in raw milk from small-scale farmers in Tanzania, highlighting the need for better antibiotic use.

Contribution

The study provides new data on the prevalence and antibiotic resistance of Staphylococcus aureus in raw milk from small-scale dairy farms in Tanzania.

Findings

Staphylococcus aureus was present in 23.9% of raw milk samples, with 16.3% being methicillin-resistant.

High antibiotic resistance was observed, with 45.9% resistant to penicillin and 20.4% being multidrug resistant.

The findings emphasize the urgent need for improved antimicrobial stewardship in dairy farming.

Abstract

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.

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.

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.

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.

The online version contains supplementary material available at 10.1186/s12917-025-05184-y.

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