Comparative resistome from toilet waste in three different income areas, Bangkok, Thailand

Antimicrobial resistance (AMR) is a significant public health threat and is associated with millions of deaths worldwide each year. Besides antimicrobial usage, different socioeconomic factors have recently gained attention as being associated with increased AMR. Bangkok, a city with diverse income levels, provided a unique setting for this study, which aimed to explore the possible within-city association between income-level areas and the diversity and abundance of AMR. Twenty-seven toilet waste samples were collected from nine different sites (low-, middle-, and high-income) during March-April 2023, and metagenomic sequencing was performed. The sequencing data were quality checked, and sequences that passed quality control were mapped to antimicrobial, metal, and disinfectant resistance gene databases as well as bacterial taxonomy databases. We observed higher antibiotic resistance genes (ARGs), metal resistance, and disinfectant resistance abundance (fragments per kilobase per million mapped reads, FPKM) in low-income groups compared to middle- and high-income groups. This included both acquired ARGs and presumed intrinsic ARGs, including genes associated with completely novel antibiotics that have so far only been identified through functional cloning. Significant differences in individual ARGs were also observed between sites. Our study highlights the relative abundance of ARGs across different income groups, emphasizing how the development of resistance mechanisms revealed through metagenomic analysis can serve as a valuable tool for city-level surveillance of AMR from toilet waste, particularly in low-income settings.