Genetic diversity of three classes of integrons in antibiotic-resistant bacteria isolated from Jiulong River in southern China
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We identified antibiotic-resistant bacterial isolates from the surface waters of Jiulong River basin in southern China and determined their extent of resistance, as well as the prevalence and characterization of three classes of integrons. A phylogenetic analysis of 16S ribosomal DNA (rDNA) sequences showed that 20 genera were sampled from a total of 191 strains and the most common genus was Acinetobacter. Antimicrobial susceptibility testing revealed that the 191 isolates were all multiresistant and there were high levels of resistance to 19 antimicrobials that were tested, particularly the β-lactam, sulfonamide, amphenicol, macrolide, and rifamycin classes. Moreover, class 1 integrons were ubiquitous while only five out of 191 strains harbored class 2 integrons and no class 3 integrons were detected. The variable region of the class 1 integrons contained 30 different gene cassette arrays. Nine novel arrays were found in 65 strains, and seven strains had empty integrons. Among these 30 arrays, there were 34 different gene cassettes that included 25 resistance genes, six genes with unknown functions, two mutant transposase genes, and a new gene. The unique array dfrA1-sat2-aadA1 was detected in all five isolates carrying the class 2 integron. We found that antibiotic-resistant bacterial isolates from Jiulong River were diverse and antibiotic resistance genes associated with integrons were widespread.
KeywordsIntegrons Antibiotic-resistant bacteria Jiulong River
This study is financially supported by the Special Fund for Agro-scientific Research in the Public Interest (No. 201203085), National Natural Science Foundation of China (No. 31202030), and Open Fund of Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences (No. KLUEH201106).
Conflict of interest
There is no financial or any other interest with regard to this paper which might be construed as a conflict of interest.
Compliance with ethical standards
Neither this paper nor any similar paper, in whole or in part, has been or will be submitted to, or published in, any other primary scientific journal. All of the authors are aware of, and agree to, the content of the paper and to their being listed as an author on the manuscript. This research is not involving human participants and/or animals.
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