engleski

Effects of Wastewater Pollution on the Antibiotic Resistance Gene Pool and Bacterial Communities in the Sediments of the Sava River, Croatia

Wastewater discharges introduce antibiotic residues and antibiotic‐resistant bacteria (ARB) into surface waters, normally rivers. Both inputs could affect river microbial communities by altering their diversity and/or functional properties as well as by expanding ARB. Here, we investigated the impact of discharges of wastewaters from production of antibiotic azithromycin on the bacterial communities and antibiotic resistome. The effects were assessed by comparing control (upstream of discharge) and impacted sites (downstream of discharge) (i) on the composition of bacterial communities and (ii) on the abundance of five macrolide-resistance genes as well as the class 1 integron‐integrase gene (intI1). Chemical analyses showed increased concentrations of macrolide antibiotics, heavy metals and nutrients in the wastewater-receiving sediments. Quantitative PCR analysis revealed a significant increase of relative abundances of targeted macrolide- resistance genes and class 1 integrons in wastewater-impacted sediments. Amplicon 16S rRNA gene sequencing showed pronounced community shift in the receiving sediments but the overall taxonomic diversity was not affected. Redundancy analysis and Mantel test indicated that macrolides and copper together with nutrients significantly correlated with community shift close to the discharge site. The number of taxa that were significantly increased in the relative abundance at the discharge site decreased rapidly at the downstream sites, showing the resilience of the indigenous sediment bacterial community. Altogether, our results showed that discharge of pharmaceutical wastewaters altered physico- chemical properties and bacterial community composition of the receiving river sediments, which contributed to the enrichment of macrolide-resistance genes and class 1 integrons.

Antibiotic resistance ; Pharmaceutical wastewaters ; Pollution ; Macrolide antibiotics

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