Effect Of Class Ⅰ Integron In Multidrug Resistant Escherichia Coli

Abstract:Objective:To investigate the distribution of classⅠintegron in local multidrug resistant Escherichia coli (E. coli), analyze the possible relationship between the classⅠintegron and multidrug resistance of E. coli, and discuss the effect of SDS on the classⅠintegron genes and the MIC of E. coli. Methods:1. Disk diffusion test:The susceptibilities of 71 E. coli strains to 4 antibiotics were detected by disk diffusion test which was recommended by NCCLS. Cefotaxime (CTX), ceftazidime (CAZ), gentamicin (G), levofloxacin (L) were chosen. E. coil ATCC 25922 was used for control.2. PCR:E. coli DNA was extracted by the Biospin bacterial genomic DNA extraction kit.3 genes of the class I integron were determined by PCR,3 pairs of primers were designed according to sequences of IntⅠ1 gene, the 5’CS and 3’CS conservative sequence of variable region, qacEDelta1-sull gene (class I integron genetic markers) of the 3’conservative side. PCR products were visualized on horizontal agarose gels with ethidium bromide after electrophoresis, and sent to detect the gene sequences.3. The class I integron were detected by PCR in the strains with SDS:The class I integron-positive E. coli strains, which were multidrug resistant, were treated with 60μg/ml SDS in 41℃, then detected by PCR and compared with those of untreated stains.4. MIC values were detected in the multidrug resistant strains with and without SDS. Results:1. Resistance results of 71 E. coli strains:(1)Resistance to commonly used antibiotics:47 strains (66.20%) were resistant to gentamicin,45 strains (63.38%) to levofloxacin,42 strains (59.15%) to cefotaxime, and 13 strains (18.31%) to ceftazidime. (2)There were 23 (32.39%) multidrug resistant strains,25 (35.21%) double-resistant strains,16(22.54%)one-resistant strains, and 7(9.86%)sensitive strains in 71 E. coli strains.2. The detection of class I integron by PCR:(1) Class I integron-positive rate of 71 E. coli strains was 84.00%. The positive detection rates of several resistance patterns had statistical difference. (2)The detection rate of 3 genes by PCR:The detection rate of IntⅠ1 genes was 74.65%, that of genetic markers genes was 78.87%, and that of variable region genes was 21.13%.3. Relationship between Class I integron and resistance:(1) Correlation with 4 antibiotics:the constituent ratios of susceptibility to gentamicin, levofloxacin and cefotaxime of integron-positive strains was statistically different with that of integron-negative strains. (2)Correlation with resistance patterns: the class I integron-positive rates were 100.00% in multidrug resistant and double-resistant strains,28.57% in sensitive strains.4. Effect of SDS:(1)The class I integron-positive rate of multidrug resistant E. coli strains was decreased statistically with SDS. (2)MIC values of multidrug resistant strains with and without SDS were statistically different. Conclusion:1. The multidrug resistant E. coli is prevalent, and the positive rate of classⅠintegron is high. The classⅠintegron is one of the important reasons of multidrug resistance.2. The detection rates of IntⅠ1 genes and genetic markers genes are higher than that of variable region genes.3. SDS has some effect on integron-positive rate and MIC of multidrug resistant E. coli.