Rapid Antimicrobial Resistance Decline Coupled with Microbial Community Shifts in Sewage Polluted River Mesocosms
Antimicrobial resistance poses a global health threat, yet the fate of antimicrobial resistance genes (ARGs) and microbial communities from wastewaters in receiving rivers is rarely quantified. This study investigated the degradation kinetics of ARGs in sewage-polluted river water mesocosms and under sulfamethoxazole and copper stress, separately and in combination. Seven clinically relevant ARGs…
Rapid declines in antimicrobial resistance (AMR) paired with shifts in microbial communities have been observed in sewage-polluted river mesocosms. This investigation examined the kinetics of AMR gene degradation and microbial community changes under stress from sulfamethoxazole and copper, individually and concurrently. Seven clinically significant AMR genes (blaCTX-M, blaNDM, qnrS, sul2, tetW, ermF, and aph(3 )-Ib), a mobile genetic element marker (intI1) and bacterial marker genes (uidA, 16S rDNA) were measured using quantitative PCR.
Bacterial community alterations were tracked through 16S rDNA sequencing. All AMR genes exhibited first-order kinetics decay, with qnrS (half-life: 8.0 hours) and blaCTX-M (8.4 hours) decreasing the fastest, and intI1 (32.5 hours) and sul2 (46.5 hours) the slowest. Analysis revealed that ARG composition primarily transformed over time, not by antibiotic or metal treatment.
Bacterial communities morphed from Campylobacterota-dominated to Pseudomonadota, Bacillota, and Actinomycetota-dominated over 168 hours, with a 95% reduction in amplicon sequence variant (ASV) richness. Predictive modeling via PICRUSt2 indicated an amplified presence of aerobic and diverse metabolic pathways as the mesocosms progressed from polluted anoxic to oxygenated conditions.
Microbial community composition shifts paralleled resistome changes, as determined by Procrustes analysis (r = 0.841, p = 0.001) and other methods. The study demonstrates that river self-purification can swiftly diminish AMR loads, particularly in warmer climates, offering approximate kinetic parameters for mathematical models to forecast AMR fates in rivers.
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