Aim: The study determined and evaluated the prevalence and antibiotic resistance of Staphylococcus aureus isolated from milk collected along the milk value chain from farm herds, milk collection center, and milk shops in Mbeya rural and Mbozi districts, Tanzania.
Materials and Methods: A total of 150 milk samples were collected; 96 from farmers' herds, 18 from milk collection centers, and 36 from milk shops. The samples were cultured in Mannitol salt agar for pathogen isolation and biochemical tests performed for confirmation of S. aureus. Kirby-Bauer disk diffusion method was employed for antibiotic resistance testing.
Results: One hundred and forty samples yielded Staphylococcus species; these were from farmer's herd (92), milk collection center (18), and milk shops (30), respectively. Biochemical tests showed that 21 (15%) were positive for S. aureus. The corresponding prevalence rates from the value chain nodes were 14.1%, 16.7%, and 16.7%, respectively. Resistance to penicillin was frequently observed (57.1%) and vancomycin was sensitive to all S. aureus isolates tested. Resistance along the sampling points showed a significant positive correlation (r=0.82, p<0.0001; r=0.65, p<0.003; and r=0.61, p<0.01) between farmers, milk collection points, and milk shops, respectively. More than half (57.1%) of the isolates exhibited resistance to three or more of the antibiotics used in this study. S. aureus isolates were shown to have a multiple antimicrobial resistance patterns, particularly with respect to penicillin, ampicillin, erythromycin, and tetracycline.
Conclusion: The level of staphylococcal isolates and the antibiotic resistance of S. aureus found in this study is an indication of subclinical mastitis, poor hygiene, and inappropriate use of antibiotics; therefore, education of farmers on subclinical mastitis control and proper use of antibiotics would be of benefits in these areas.
Antibiotic resistance of Staphylococcus aureus isolates from milk produced by smallholder dairy farmers in Mbeya Region, Tanzania
