Detection of drug resistance genes in integron of Shigella sonnei from six cities of Jiangsu Province in 2011 / 中华传染病杂志

ABSTRACT

Objective To investigate the resistance status of different integrons of Shigella sonnei (S.sonnei) and to analyze the distribution of resistant genes in integrons in Jiangsu Province.Methods A total of 32 strains of S.sonnei isolated from six cities of Jiangsu Province in 2011 were collected.The antibiotic susceptibility was tested by disk diffusion method.The molecular homology was analyzed by pulsed field gel electrophoresis (PFGE).The detection and classification of integrons were achieved by analyzing the positive polymerase chain reaction (PCR) products using restriction fragment length polymorphism (RFLP).RFLP and DNA sequencing were used to analyze the resistance genes in integrons.Results Multi-drug resistance (MDR) was detected in 28 (87.5％) S.sonnei strains.The resistant rates to ampicillin,nalidixic acid and tetracycline were highest (87.5％,respectively).However,it was sensitive to norfloxacin.PFGE analysis showed that there were 3 kinds of homologous clones involving 31 strains of the 32 S.sonnei strains.Among them,2,5 and 24 strains had the same clones,respectively.Accordingly,they spread within one,two and five different cities.The detection rates of class 1,class 2 and the atypical class 1 integrons in S.sonnei were 62.5％ (20/32),81.3％ (26/32) and 21.9％ (7/32),respectively,and no class 3 integron was detected.Sequence analysis of class 1 integron variable area revealed that it contained multiple resistant genes (aacA4-cmlA1 and dfrA1-aadA 1) ; dfrA1-sat 1-aadA 1 from class 2 integron and blara-30-aadA 1 from atypical class 1 integron were also identified.Conclusions In 2011,homologous S.sonnei strains spread among different cities in Jiangsu Province.MDR strains are prevalent and integrons are widespread which mediated the emergence of MDR strains.