Introduction: Freshwater ecosystems provide propitious conditions for the acquisition and spread of antibiotic resistance genes (ARGs), and integrons play an important role in this process.
Material and methods: In the present study, the diversity of putative environmental integron-cassettes, as well as their potential bacterial hosts in the Velhas River (Brazil), was explored through intI-attC and 16S rRNA amplicons deep sequencing. RESULTS AND DISCUSSION: ORFs related to different biological processes were observed, from DNA integration to oxidation-reduction. ARGs-cassettes were mainly associated with class 1 mobile integrons carried by pathogenic Gammaproteobacteria, and possibly sedentary chromosomal integrons hosted by Proteobacteria and Actinobacteria. Two putative novel ARG-cassettes homologs to fosB3 and novA were detected. Regarding 16SrRNA gene analysis, taxonomic and functional profiles unveiled Proteobacteria, Bacteroidetes, Firmicutes, and Actinobacteria as dominant phyla. Betaproteobacteria, Alphaproteobacteria, and Actinobacteria classes were the main contributors for KEGG orthologs associated with resistance.
Conclusions: Overall, these results provide new information about environmental integrons as a source of resistance determinants outside clinical settings and the bacterial community in the Velhas River.
Keywords: 16S rRNA gene; Antibiotic resistance; Environmental integron-cassettes; Urban river microbiome.