Study On The Relationship Between Multidrug Resistance And Class Ⅰ Integron Of E.coli From Swine Farms In Chongqing

The pathogenic E.coli are the most popular pathogeny bacteria in clinic with serious harm to the development of husbandry. As antibacterial is widely used, the problem of drug-resistance increased seriously. Invesitigate the level of antibiotic resistance in pathogenic E.coli strains isolated from swine farms collected in Chongqing, the frequency of the multidrug resistance strains carrying class 1 integron, the relationship between the gene cassettes of the integron carride by the strain with its antibiotic resistance profile. This study can help us make clear of the mechanism of drug-resistance transferring in gene level.Antimicrobial susceptibility testing of 26 antimicrobial agents was performed on a total of 101 commensal pathogenic E.coli isolates collected from pigs industry. Antibiograms and their interpretation were made using the disk diffusion method following the NCCLS (2006) standards. The results of the study showed that all isolate presented a multiple antibiotic resistance, the resistance rate of pathogenic E.coli isolates to tetracycline, penicillin, rifampin and clarithromycin was 100%, the resistance rate of pathogenic E.coli to lincomycin, aminobenzyl penicillin, erythromycin and trimethoprim-sulfamethoxazole were exceeded 90%, the resistance rate to cefazolin, cefradine and cefoperazone was relative lower, the style of the drugs resistance of pathogenic E.coli was concentrate in 18-22 kinds; The resistance rate of pathogenic E.coli is increasing, there is a significantly increasing tendency of multi-resistance, the problem of bacterial resistance is getting worse.According to the construction of I integron, we designed 3 pairs of primers to amplify intI1 gene, variable segment, 3-conserved segment for detectting pathogenic E.coli's I integron. The results of the study showed that he presence and genetic content of class I integron were examined with specific primers of class I integron by PCR, The detection rate of I integron of 101 E.coli was 66.3%.We use endonuclease Hinfl to digest PCR products of the variable segment; We mensurated the sequence of different length of variable region PCR products, using Blast in GenBank to analysis the gene cassettes that variable region carried. The results of the study showed that the variable segment with the same length has the same cleavage map, the different length has different cleavage map. The results showed that the variable segment with same length carrying the same gene cassette. The I integron we amplified carried dfrA12, dfrA17, aadA1, aadA2, aadA5, aadB and cmlA6, coding the resistance genes resistant to streptomycin-spectinomycin, gentamicin-kanamycin and chlorampliouicol.According to the results of this test ,we analysised the relationship between I integron and multi-drug resistance. The type of gene cassettes that single strains carried has no obviously corresponding relationship with phenotype, but integrons were relatively distributing centralized in resistant strains, The test results show that I integron positive strains were centralized resistant to 18-22 medicines. In 65 pathogenic E.coli strains that resistant to 18-22 medicines, I integron was detected 51 strains, the detection rate was 78.5%.