Carriage rates of class 1, class 2 integrons as well as ISCR1 in Shigella isolates and their relationship with drug resistance

DONG Lijuan; YANG Xian; WANG Jun; QI Wei; LYU Xing; LIANG Fan

doi:10.11958/j.issn.0253-9896.2015.04.018

Abstract：Objective To explore carrying rates of class 1, class 2 integrons as well as ISCR1 in Shigella isolates and their connection with drug resistance. Methods Antibiotic sensitivities were detected by K-B disk diffusion in 159 clinical isolates. Total bacteria DNA was prepared through boiling the isolates and the DNA was then used as template for PCR am?plification. PCR, ZSCR1 and sequencing analyse of integrons were applied to all of them. Results were compared by Blast and GenBank. Results Antibiotic sensitivity results showed that in the S. flexneri strains the incidence of resistance to tet?racycline and streptomycin were 88.68%and 81.13%in the S. flexneri strains while the incidence of resistant to chloram?phenicol and trimethoprim-sulfamethoxazol were both 56.60%, and the incidence of multidrug drug resistance was 77.36%. In the sonnei strains, the incidence of resistance to ampicillin, trimethoprim-sulfamethoxazo were 97.17% and 95.28%, 83.96%and 76.42%respectively, and the incidence of multidrug resistance was 98.11%. Among all isolates, 118 were class 1 integron positive , 70 were class 2 integron positive and 89 were double positives. For those 118 isolates that are positive of class 1 integron, 23 were typical while 95 weres atypical. The gene cassettes of typical class 1 integrons contains aadA2, aa?dA1, dfrⅠ, blaoxa-10 and blaoxa-1. IntI1, aadA, blaoxa-1 and IS1 were included in the gene cassetes of the atypical class 1 integrons. Class 2 integrons positive isolates carried gene cassttes which include dfrA1, satl and aadA1. No ISCR1 was found in any isolate. Integron carriage strains were closely associated with higher rate of multiple antibiobic resistance com?pared with the organisms without integrons (90.65%,50%, P<0.05). Conlusion Class 1 and class 2 integrons were widely existence in Shigella isolates and were related to the multidrug resistance.