engleski

Pollution from azithromycin-manufacturing promotes the spread of antibiotic-resistance genes and alter bacterial community in receiving river sediments

Introduction: Effluents from antibiotic manufacturing may contain high concentrations of antibiotics, which are the main driving force behind the selection and spread of antibiotic resistance genes (ARGs) in the environment. Objective: To explore the impact of the discharge of effluents from an azithromycin- production on the antibiotic resistome and bacterial communities in sediments from the receiving Sava river (Croatia). Methods: We analyzed industrial effluent as well as upstream and downstream river sediments by chemical analyses, quantitative PCR, plasmid capture and amplicon 16S rRNA gene sequencing. Results: Chemical analyses indicated that manufacturing discharges significantly increased the amount of macrolide antibiotics, heavy metals and nutrients in the receiving river sediments. Quantitative PCR revealed a significant increase of relative abundances of various ARGs and mobile genetic elements (IncP- 1 plasmids, class 1 integrons) in receiving sediments. In addition, industrial discharges considerably increased plasmid-mediated horizontal transfer of ARGs from polluted sediments into E. coli as shown by biparental mating experiments. Amplicon sequencing of 16S rRNA genes showed strong shift in sediment community composition at the discharge site that correlated with macrolide, copper and nutrient levels. The number of taxa that were significantly increased in relative abundance at the discharge site decreased rapidly at the downstream sites, showing the resilience of the indigenous sediment bacterial community. Conclusion: This study showed that the discharge of insufficiently treated industrial effluents altered physicochemical characteristics and bacterial community of receiving river sediments, which contributed to the enrichment of ARGs, thereby increasing a risk for transfer of these genes to human pathogens. Actions are therefore urgently needed to reduce risks at such locations.

macrolide resistance ; antibiotic manufacturing ; pollution ; sediment ; macrolides ; bacterial community

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