Objectives: The rapid emergence of drug-resistant Shigella sonnei is a serious public health problem. This study aimed to characterise the antimicrobial resistance patterns, molecular subtypes, and integron types and resistance gene cassettes in S. sonnei from Jiangsu Province, China.
Methods: In total, 340 S. sonnei were collected in 2002-2011 throughout Jiangsu Province. Antimicrobial susceptibility testing, pulsed-field gel electrophoresis (PFGE), PCR amplification of integrons, restriction fragment length polymorphism (RFLP) and DNA sequencing of cassette regions were performed.
Results: Resistance rates to ampicillin (67.7%), nalidixic acid (75.2%), tetracycline (73.7%) and trimethoprim/sulfamethoxazole (68.7%) remained high. Strains from Centre and South Jiangsu showed higher resistance and multiresistance rates compared with the North. PFGE analysis indicated that large-scale clonal transmission among different cities occurred several times during 10 years. Among all strains, 55.9% (190/340) harboured class 1 integrons, 80.3% (273/340) harboured class 2 integrons and 49.4% (168/340) harboured an atypical class 1 integron. Resistance rates to nine antimicrobials in the class 1 integron-positive group were significantly higher than in the negative group (P<0.05). Seven different gene cassettes were detected in class 1 integrons. The most prevalent type was aacA4-cmlA1 (114/286). Class 2 integrons carried the gene cassette array dfrA1-sat1-aadA1, and the atypical class 1 integron carried blaOXA-30-aadA1.
Conclusions: The increasing antimicrobial resistance and significant clonal transmission of S. sonnei circulating in Jiangsu were closely related to the high prevalence of integrons and gene cassettes. Long-term cross-regional monitoring of antimicrobial resistance is urgently required for S. sonnei.
Keywords: Integron; Multidrug-resistant; PFGE; Resistance; Shigella sonnei.
Copyright © 2017 International Society for Chemotherapy of Infection and Cancer. Published by Elsevier Ltd. All rights reserved.