Assessment of Antimicrobial Resistance Genes and Pathobiome Diversity in Domestic Wastewater of a Tropical Country

Wastewater treatment plants (WWTPs) are recognised as key hotspots for the dissemination of antimicrobial-resistant bacteria and antimicrobial resistance genes (ARGs). However, studies addressing the role of domestic WWTPs in the spread of resistance traits in tropical regions remain limited. This study evaluated a domestic WWTP during dry and rainy seasons to examine its role as a reservoir and dissemination hub for ARGs and potential bacterial pathogens. The WWTP demonstrated stable physicochemical removal efficiencies, although its performance slightly decreased during the rainy season. Notably, the relative abundance of ARGs measured by qPCR was higher in the effluent than in the influent of the WWTP. Metagenomic analysis of activated sludge revealed that chromosomally encoded ARGs conferred resistance to macrolides, aminoglycosides, rifamycin, sulphonamides, and tetracyclines. In contrast, plasmid-associated ARGs were primarily linked to resistance against quaternary ammonium compounds (QACs), indicating the presence of a potential conjugative plasmid facilitating the mobility and persistence of QAC resistance genes within the microbial community. Furthermore, pathobiome analysis identified a high relative abundance of potential pathogens, including genera Gordonia, Acidovorax, Pseudomonas, and Mycobacterium members. These findings highlight the role of domestic WWTPs as reservoirs and potential amplifiers of antimicrobial resistance in tropical environments.