Characterization of integrons, extended-spectrum beta-lactamases, AmpC cephalosporinase, quinolone resistance, and molecular typing of Shigella spp. from Iran

Abstract

Introduction: The wide distribution of extended-spectrum beta-lactamase (ESBL) producing Shigella spp., along with the emergence of fluoroquinolone resistant isolates, is a serious threat to public health, posing a new challenge for the effective treatment of shigellosis. The purpose of this study was to determine the level of antimicrobial resistance, the presence of genes encoding resistance to cephalosporins, and plasmid-mediated quinolone resistance (PMQR) among the clinical isolates of Shigella spp. in Iran. Materials and methods: A total of 142 Shigella isolates were collected from different parts of Iran. All of the cephalosporin resistant Shigella strains were selected based on ESBL and AmpC production. The presence of PMQR regions was assessed in ciprofloxacin-resistant isolates, and genetic relatedness in the isolates was determined. Results: Seventy-eight Shigella isolates were found to be resistant to extended-spectrum cephalosporin (ESC). The bla(CTX) (M15) was the most prevalent cephalosporinase. Four ESBL-producing isolates were also resistant to ciprofloxacin. Among the PMQR regions, aac(6')-lb-cr gene was the most prevalent, as it was seen in 83.3% of the ciprofloxacin resistant isolates, while qnrh was positive in 16.7%. Clonal relatedness showed a limited variety of clones was responsible for Shigella infection in the region studied. Conclusion: Overall, our findings indicated that a large number of ESBL producing Shigella spp. were mediated mainly by bla(CTX-M15)- This study is the first report on ciprofloxacin-resistant ESBL-producing Shigella isolates from patients in Iran.