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Abstract

Bovine mastitis, particularly subclinical mastitis (SCM), is a major concern in dairy cattle due to its asymptomatic nature and significant economic impact. In Asia, Staphylococcus aureus and coagulase-negative staphylococci (CoNS) are key pathogens. The overuse of antibiotics has led to the emergence of multidrug-resistant (MDR) bacteria, posing risks to animal health and food safety. This study aimed to identify staphylococci associated with SCM and assess their antibiotic resistance (AR) profiles. Milk samples were collected from 20 cows at a dairy farm in Malacca, Malaysia, in August and October 2023. SCM was diagnosed using the California Mastitis Test (CMT), and bacterial isolates were cultured on Mannitol Salt Agar (MSA). Antibiotic susceptibility was assessed using the Kirby-Bauer disk diffusion method. CMT results indicated 56% of samples were SCM-positive. From 153 isolates, 84 were presumptive coagulase-positive staphylococci (CoPS) and 69 were CoNS. AR profiling revealed 52% resistance to penicillin, 12% to cefoxitin, and 5% to tetracycline; all isolates were susceptible to erythromycin. Kruskal-Wallis analysis showed significant differences in antibiotic susceptibility across both CoPS and CoNS (P < 0.001), indicating variable susceptibility patterns. Sequencing analysis of the sodA gene identified that 50% of isolates were Staphylococcus, 33% were Macrococcus, and 17% were Macrococcoides, highlighting their roles in mastitis and AR. This study highlights the importance of SCM and the need for monitoring AR in dairy cattle. These findings emphasize the importance of SCM surveillance and AR monitoring. The emergence of resistance is likely linked to recurrent antibiotic use, underscoring the need for prudent antimicrobial strategies in dairy herd management.

Keywords

Antibiotic resistance, Bovine mastitis, Milk, Subclinical mastitis, Staphylococci

Article Type

Special Issue Article

First Page

191

Last Page

203

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

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