Milk supply chain as a reservoir of antimicrobial-resistant Staphylococcus species

Abstract

Milk is a source of essential nutrients, but food safety across the milk supply chain has emerged as an integral part of food trade. Of the several food safety hazards, antimicrobial-resistant Staphylococcus species have emerged as one of the major microbial hazards with significant public health concerns. The present cross-sectional study was undertaken with the objective to isolate Staphylococcus species from the milk supply chain, characterize isolates for antimicrobial resistance, and trace the origin of isolates using molecular techniques. Samples collected from the formal and informal milk supply chains showed prevalence of Staphylococcus species of 4.3% (n=720); isolates were identified as coagulase-positive (S. aureus 67.7% and S. intermedius 6.4%) and coagulase-negative (S. lentus 9.6%, S. sciuri 3.2%, S. xylosus 3.2%, S. schleiferi 3.2%, S. felis 3.2%, and S. gallinarum 3.2%) species. Staphylococcus isolates showed antimicrobial resistance to methicillin (32.2%), β-lactam (41.9%), and macrolide-lincosamide-streptogramin B (3.2%). Staphylococcus isolates phenotypically resistant to methicillin also carried the mecA gene and displayed diverse pulsed field gel electrophoresis (PFGE) profiles, indicating their diverse origins in the milk supply chain. Based on the similarity of PFGE profile, the origin of one of the Staphylococcus isolates was traced to the soil in contact with milch cows. The findings of this study highlight the need for more comprehensive microbial risk analysis studies across the milk supply chain, capacity building, creation of awareness among stakeholders about the judicious use of antimicrobials, and protection of public health using a One-Health approach.