Biochemical analyses can complement sequencing-based ARG load monitoring: a case study in Indian hospital sewage networks

Antibiotic resistance is an emerging global crisis which has been estimated to cause increasing numbers of deaths. Low and middle-income countries (LMICs) are challenged with a larger burden of antibiotic resistance, as antibiotic resistance is more common in LMICs, and access to antibiotics and health care is often limited compared to high-income countries. Further exacerbating the issue is the possible lack of efficient treatment of hospital sewage which can have high concentrations of clinically relevant antibiotic-resistant pathogens. Monitoring of antibiotic resistance genes (ARGs) in sewage along the sewage networks (from hospitals to community sewers and sewage treatment plant effluents) would provide crucial tools for identifying hotspots of ARG pollution. However, the methods that are currently used to quantify ARGs rely on expensive shotgun sequencing or qPCR. Therefore, we investigated whether ARG load monitoring could be complemented with inexpensive standard biochemical analyses. Our results show that across four different sewage networks and three seasons, biological oxygen demand (BOD) and total organic carbon (TOC) can provide robust indicators of total ARG load. This lays grounds for finding cost-efficient techniques for sewage ARG pollution monitoring in low-resource settings.