Risks of antibiotic resistance genes and antimicrobial resistance under chlorination disinfection with public health concerns.

As a widely used disinfection technology, the effects of chlorination on antibiotic resistome and bacterial community received great scientific concerns, while the pathogens associated health risks kept largely unknown. With this concern, the present study used metagenomic analysis combined with culture method to reveal chlorination effects on antibiotic resistance genes (ARGs) and their bacterial hosts (total microbes and Escherichia coli) through simulating the chlorination dosage with human health concerns (drinking water and swimming pool). The resistome profiling showed that chlorination process could significantly decrease both abundance and diversity of total ARGs, while with limited removal rates of 6.0-8.7% for opportunistic pathogens E. coli isolates. Of all the observed 515 ARG subtypes, 105 core subtypes were identified and persistent during chlorination for both total microbes and E. coli. Antibiotic susceptibility test showed that chlorination treatment could efficiently remove multi-resistant E. coli isolates but select for tetracycline resistant isolates. Five ARG-carrying genomes (assigned to Bacteroidetes, Firmicutes, Actinobacteria) enriched by 18.1-102% after chlorination were retrieved by using metagenomic binning strategies. Bray-Curtis dissimilarity, network and procrustes analyses all indicated the remained antibiotic resistome and bacterial community were mainly chlorination-driven. Furthermore, a systematic pipeline for monitoring chlorination-associated antimicrobial resistance risks was proposed. These together enhance our knowledge of chlorination treatment associated public concerns, as important reference and guidance for surveillance and control of antibiotic resistance.