ANTIMICROBIAL RESIDUES IN INFORMAL MILK SUPPLY CHAINS AND THEIR LINK TO COMMUNITY ANTIBIOTIC RESISTANCE PATTERNS

Abstract

Background: Antimicrobial resistance (AMR) is an increasing global health concern, and food-producing animals are considered important contributors to the development and spread of resistant bacteria. Informal milk supply chains are widely used in Pakistan; however, limited monitoring and inappropriate antimicrobial practices may increase the risk of antibiotic residues entering the human food chain.

Objective:  This study aimed to investigate antimicrobial residues in raw milk from informal dairy sources and evaluate their possible association with antimicrobial resistance patterns among community commensal bacteria.

Study type: Cross-sectional + lab-based surveillance

Methods: A cross-sectional laboratory-based surveillance study was conducted in Lahore. Raw milk samples were collected from informal dairy vendors and small-scale farms and screened for antimicrobial residues using microbiological and confirmatory laboratory methods. A structured questionnaire was used to assess household milk consumption patterns, exposure frequency, and handling practices. Commensal bacterial isolates, including Escherichia coli and Enterococcus species, were obtained from participating households and evaluated for antimicrobial susceptibility using standard microbiological procedures. Data were analyzed to compare resistance patterns between higher and lower milk exposure groups. Results: Antimicrobial residues were detected in a considerable proportion of analyzed milk samples, with higher contamination observed among vendor-level samples compared with farm-level samples. Households with frequent consumption of informal milk demonstrated increased carriage of antimicrobial-resistant bacterial isolates compared with households with lower exposure. E. coli and Enterococcus isolates from highly exposed households showed greater resistance against commonly used antimicrobial agents, indicating a possible relationship between informal milk exposure and community resistance patterns.

Conclusion: The findings suggest that informal milk supply chains may represent an important pathway for antimicrobial residue exposure and the circulation of resistant bacteria within communities. Strengthening antimicrobial stewardship among dairy producers, improving milk safety surveillance, enforcing withdrawal periods, and increasing consumer awareness are essential measures for reducing AMR risks. A coordinated One Health approach involving veterinary, agricultural, food safety, and public health sectors is required to control antimicrobial resistance linked with dairy production systems.