Truncated Class 1 Integron Gene Cassette Arrays Contribute to Antimicrobial Resistance of Diarrheagenic Escherichia coli

Abstract

Class 1 integrons (c1-integrons) are associated with multidrug resistance in diarrheagenic Escherichia coli (DEC). However, little is known about gene cassettes located within these c1-integrons, particularly truncated c1-integrons, in DEC strains. erefore, the aims of the present study were to reveal the relationship between antimicrobial resistance and the presence of truncated c1-integrons in DEC isolates derived from human stool samples in Japan. A total of 162 human stool-derived DEC isolates from Japan were examined by antimicrobial susceptibility testing, PCR-based gene detection, and next-generation sequencing analyses. Results showed that 44.4% (12/27) of c1-integrons identified in the DEC isolates harbored only intI1 (an element of c1-integrons) and were truncated by IS26, Tn3, or IS1-group insertion sequences. No difference in the frequency of antimicrobial resistance was recorded between intact and truncated c1-integron-positive DEC isolates. Isolates containing intact/truncated c1-integrons, particularly enteroaggregative E. coli isolates, were resistant to a greater number of antimicrobials than isolates without c1-integrons. aadA and dfrA were the most prevalent antimicrobial resistance genes in the intact/ truncated c1-integrons examined in this study. erefore, gene cassettes located within these intact/truncated c1-integrons may only play a limited role in conferring antimicrobial resistance among DEC. However, DEC harboring truncated c1integrons may be resistant to a greater number of antimicrobials than c1-integron-negative DEC, similar to strains harboring intact c1-integrons.

Characterization of antimicrobial susceptibility, extended-spectrum β-lactamase genes and phylogenetic groups of Shigatoxin producing Escherichia coli isolated from patients with diarrhea in Iran

“…Overuse of antibiotics with and/or without prescription is responsible for emergence of multidrug resistance among clinical isolates, which is a serious public health issue and can create therapeutic difficulties for patients. The findings of this study show high levels of resistance to ampicillin, trimethoprim–sulfamethoxazole and tetracycline among STEC, which is in agreement with previous findings in Japan, China, South Africa, Iran, Mexico and Michigan [ 24 – 29 ]. Also relatively lower levels of resistance to cefotaxime, ceftazidime, ciprofloxacin and levofloxacin was revealed, a finding which was similar to those reported by others [ 30 , 31 ], and opposite to that reported by Zhang et al in china [ 25 ].…”

“…Similar pattern was reported from India [ 30 ]. The prevalence of MDR was 60.9%, which was both lower [ 25 ] and higher [ 24 ] than results reported by others. Furthermore, almost all of the ESBL-producing STEC strains were MDR.…”

Characterization of Integrons and Quinolone Resistance in Clinical Escherichia coli Isolates in Mansoura City, Egypt

“…is indicates that quinolone resistance genes are not cassette-born. is coincides with the study of Kubomura et al who found that except for dfrA and aadA genes, the antibiotic resistance genes are mostly found outside the integrons [69].…”

“…e reported cassettes encode for resistance to trimethoprim and aminoglycosides and have been recorded among class I integrons in previous studies [10,13,61,68,69]. e diversity of class I integron cassettes is comparable to previous studies [10,61] that reported 10 and 7 different gene cassettes among the tested isolates, respectively.…”

“…In the current study, 23 out of 42 class I integron positive isolates carried 7 different gene cassettes ( dfrA7 , dfrA12 , dfrA17 , dfrB4 , aadA22 , dfrA17-aadA5 , and aadA2-orfF-dfrA12 ). The reported cassettes encode for resistance to trimethoprim and aminoglycosides and have been recorded among class I integrons in previous studies [ 10 , 13 , 61 , 68 , 69 ]. The diversity of class I integron cassettes is comparable to previous studies [ 10 , 61 ] that reported 10 and 7 different gene cassettes among the tested isolates, respectively.…”