O-20 Hidden threats beneath the surface: antibiotic resistance in pig farm runoff water
Author(s):
M Matthew-Bernard, M Russo, K Farmer- Diaz, V Matthew-Belmar, S Cheetham, K Mitchell, CNL Macpherson, ME Ramos-Nino
Year of Presentation:
2026
Objective: Antimicrobial resistance (AMR) is a growing
global health threat driven by antibiotic misuse in human
medicine and livestock production. Intensive pig farming
contributes to environmental AMR through the release of
antibiotic-resistant bacteria (ARB) and antibiotic resistance
genes (ARGs) into surrounding ecosystems. Within a One
Health framework, pig farm wastewater represents a key
interface linking agricultural, environmental, and human
reservoirs of resistance. This pilot study aimed to detect and
characterize selected ARGs-bla-SHV, bla-OXA-20, sul1,
mcr-1, and intI1 in pig farm runoff water in Grenada to
establish baseline data for regional surveillance.
Methods: Wastewater runoff samples (2 L each) were collected from eight pig farms across multiple parishes in Grenada in November 2025. Samples were processed for DNA extraction using the PowerSoil® DNA Isolation Kit, and ARGs were detected via polymerase chain reaction (PCR) amplification using gene-specific primers. Amplicons were visualized through agarose gel electrophoresis and compared with molecular weight standards to confirm gene presence.
Results: All samples were positive for bacterial 16S rRNA genes, confirming DNA quality. The detection frequencies for ARGs were as follows: intI1 (100%), sul1 (100%), bla-SHV (62.5%), bla-OXA-20 (12.5%), and mcr-1 (12.5%). The co-occurrence of intI1 and sul1 suggests sustained selective pressure from agricultural antibiotic use.
Conclusion: The widespread detection of clinically relevant ARGs underscores pig farm runoff water as an important environmental reservoir of AMR in Grenada. The presence of bla-SHV and mcr-1 genes associated with human pathogens and last-resort antibiotics, raises significant public health concerns. Continuous monitoring and improved wastewater management are crucial to mitigate environmental dissemination and prevent cross-domain transmission of resistance within the One Health spectrum.