Role of Escherichia coli strain subgroups, integrons, and integron-associated gene cassettes in dissemination of antimicrobial resistance in aquatic environments of Jinan, China

Aquatic environments are known reservoirs of antibiotic-resistant bacteria, but little information is known about the role of Escherichia coli strain subgroups, integrons, and integron-associated gene cassettes in the prevalence of antimicrobial resistance. To address these knowledge gaps, the diversity and distribution of drug-resistant E. coli strains and their integrons in hospital wastewater (HWW) and XiaoQing River water (XQRW) in Jinan, China were compared. Phylogenetic assays showed that the isolates were distributed in every E. coli subgroup. The prevalence of antibiotic resistance in each E. coli subgroup from HWW was higher than in subgroups from XQRW, except for phylogenetic subgroup A(0). Classes 1 and 2 integrons were found in 327 strains (78.2% of the total 418 isolates) with a prevalence of 85.6% among the 209 isolates from HWW. Among 15 gene cassette arrays, dfrA17-aadA5 and dfrA12-orfF-aadA2 were the most prevalent. The prevalence of drug-resistance gene cassettes and diversity of arrays further proved that integrons were important contributors to the widespread occurrence of antibiotic resistance in E. coli among Jinan aquatic environments.