| Bacillary dysentery which the shigella was the pathogen had been found more than 100 years of history.It was a common acute intestinal infectious diseases.It was in the third of the notifiable infectious diseases incidence. The number of patients per year was close to 500000,and was at the top in the 37 monitoring infectious diseases. It posed a serious threat to public health[1]. With the development of our national economy, the incidence rate decreased year by year. With the widespread use of antibiotics, the drug resistance of Shigella rate increased and showed multiple resistance. Integron and insertion sequence common region(ISCR) used as a mobile element, were closely related with the emergence of bacterial resistance and multi-drug resistance[2].Integron consisted of 5’conserved segment( 5’CS),3’conserved segment( 3’CS) and the variable region between the two conserved segment. The integration of 5’CS including integrase gene(Intl), att I and Pant; variable region gene box with different number, which had been found more than 70 kinds[3]; 3’ CS region varied due to different types of integron. It had been divided into 10 categories. Researching shows, class 1, class 2 integrons were closely related with multi-drug resistance in Shigella spp[4].ISCR could move bacterial DNA to any nearby[ 5]. The ISCR element was related with a lot of resistance.These resistance genes were captured by ISCR which were not the original genomes of host. So the ISCR1 posed a serious threat to the existing nti infection scheme,especially gram negative bacteria scheme. Objective: To explore the carrying rates of class 1,class 2 integrons as well as ISCR1 in Shigella isolates and their connection with the drug resistance. Materials and methods: The strains were collected from the fecal samples of three hospitals.The total strains was 159. Used the serum agglutination to identify the serological groups. Antibiotic susceptibility was detected by the K-B disk diffusion method for 159 clinical isolates. The boiling method was used to prepare the bacterial total DNA as the template for PCR amplification. PCR and sequencing analysis of integrons and ISCR1 were applied to all of them. Results were compared by Blast program and Gen Bank database. Results:The antibiotic susceptibility results showed that in the S. flexneri strains the incidence of resistance to tetracycline and streptomycin were 88.68% and 81.13%, to chloramphenicol and trimethoprim-sulfamethoxazol were both 56.60%, and the incidence of multidrug resistance was 75.47%. In the sonnei strains, the incidence of resistance to ampicillin and trimethoprim-sulfamethoxazo were 97.17% and 95.28%, to tetracycline and getamycin were 83.96% and 76.42%, and the incidence of multidrug resistance was 98.11%. Class 1 integrons was 118, class 2 integrons was 89 and both were 70. The class 1 integrons positive isolates contained 23 isolates typical class 1 integron and 95 isolates atypical class 1 integrons. The gene cassetes of typical class 1 integrons aad A2, aad A1, dfrⅠ, blaoxa-10 and blaoxa-1 were detected. The int I1, aad A, blaoxa-1 and IS1 composed the gene cassetes of the atypical class 1 integrons. Class 2 integrons positive isolates carried gene cassttes dfr A1, satl and aad A1. No ISCR1 was found. Integron carriage strains were significantly associated with higher rate of multiple antibiobic resistance than the organisms without integrons(91.97% vs 81.81%). Conclusion:The main serotypes of Shigella spp. Were S.sonnei and S.flexneri in Tianjin,China. The multi-drug rate is 90.57%. S.flexneri is 77.47% and S.sonnei is 98.11%. Class 1 and class 2 integrons were widely existence in shigella isolates and were related to the multidrug resistance. |
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