Study On The Drug Resistance Of Clinically Escherichia Coli Isolates In Ningxia

In order to investigate the resistance of clinically E. coli isolates in Ningxia, molecular detection of resistance genes of182E. coli isolates were carried out using PCR; resistance phenotype were determined by disk diffusion method, Meanwhile, relationship between pathogenicity, serotypes and drug resistance were analysed. The results are as follows:1. According to the reference sequence reported by Genbank, a total of25kinds of resistance gene PCR-specific primers were designed:sulfa drug resistance gene:sull, sul2, sul3; tetracyclines resistance gene:tetA, tetB, tetC, tetD, tetE, tetG; aminoglycoside resistance genes: aadB, aadD, aadAl, aadA2, aacC2, aacC4, aac (3)-Ia, aac (3)-Ilay aph (3)-IIa;chloramphenicol drug resistance genes:Cat], CmlA, Flor;β-lactamdrug resistance gene:CTX-M, SHV, OXA, TEM, PCR detection method of resistance genes was established. The results showed that the expected size fragment was amplified from resistance gene-positive strains, while the negative strains and blank control were not. Suggesting that the PCR method was specific and sensitive, and it can be used as a method for the detection of resistant gene of E. coli clinical isolates.2. Furthermore, molecular distribution of25drug resistance genes in182E. coli isolates were detected using established PCR method. The results indicated that17resistance genes in total were detected, positive rate of different resistance gene are sull(62.6%),sul2(46.7%),sul3(1.6%),tetA(40.1%),tetB(33.5%),aadA](8.2%),aadA2(8.2%),aacC2(41.8%),aacC4(17.0%),aac(3)-IIa(45.1%),aph(3)-Ila(6.6%),Catl(16.5%),CmlA(7.1%),Flor(4.9%), CTX-M(20.3%),OXA(12.6%) and TEM(54.4%) respectively.8resistance genes of tetC, tetD, tetE, tetG,aadB,aadD,aac(3)-Ia and SHV were not detected.3. The susceptibility testing of five categories of12kinds of antimicrobial drugs of182E. coli isolates were carried out through K-B disk diffusion method recommended by CLSI. The results showed that182strains varied in resistance to12antimicrobial drugs. Drug resistance rate are as follows:ampicillin (86.3%), amoxicillin (85.7%), tetracycline (74.7%), cotrimoxazole (63.7%),gentamicin(52.7%),cefotaxime(38.5%),tobramycin(29.1%),kanamycin(25.3%),doxycycli ne(19.2%), chloramphenicol (18.7%), amikacin (8.8%) and ceftazidime (8.2%). There are86resistant spectrums among182E. coli isolates, most are multiresistant.4. Pathogenicity analysis indicated that there were145pathogenic E. coli among182E. coli isolates.Among the145pathogenic strains,135strains are drug resistant, drug resistance rate of pathogenic E. coli amounts to93.1%. Suggesting that the pathogenicity and drug resistance of E. coli isolates are highly correlated.5.Based on previous182E. coli serotypes identification, in the present study,we analysed the correlation between serotypes and resistance of the E. coli isolates. The results showed that more than69%strains resisted to ampicillin, amoxicillin, tetracycline and co-trimoxazole of dominant01and05serotype strains; over60%strains resist to cotrimoxazole, ampicillin, amoxicillin, tetracycline and gentamicin of dominant018, O101and0111strains; more than80%strains resist to tetracycline, ampicillin and amoxicillin02serotype strains. More than54%strains resist to ampicillin, amoxicillin, tetracycline, cotrimoxazole and cephalosporin cefotaxime among078serotype strains.