An antimicrobial resistance gene situationer in the backyard swine industry of a Philippine City

Antimicrobial resistance (AMR) as a result of antimicrobial overuse and misuse in agriculture is a growing concern, especially in the predominant but poorly regulated backyard or smallholder swine farms of the Philippines. A city-scale surveillance of antimicrobial resistance genes (ARGs) was conducted through selected backyard swine farms to obtain a comprehensive understanding of the AMR situation in the backyard sector of Davao City, Philippines. The ARGs encoding resistance to four antimicrobial classes (β-lactams: bla_CTX-M, bla_OXA, bla_SHV, bla_TEM, mecA; quinolones: qnrS and qnr-A2; macrolides: ermA and ermB; tetracycline: tetM) were quantified in swine feces via real-time PCR, and point maps were generated to visualize the ARG geographic distribution. The ARGs bla-_TEM, ermB, qnrS, and tetM were detected in all farms at relatively intermediate to high levels, consistently representing the four most used antimicrobial classes in Philippine farms. All the investigated ARGs were present in some local barangay units, indicating potential emergence of AMR hotspots. A 0.5 quantile regression analysis identified specific backyard farm attributes associated with ARG occurrence and diversity, which may influence the ecological spread of the ARGs. These findings provide support for evidence-based guidelines to reinforce a One Health framework for the Philippine National Action Plan to Combat AMR.