Study On Extended-spectrum β-lactamases-producing Phenotype And Genotype In Isolates Of Escherichia Coli From Fuzhou

Objective: On the basis of investigation of antibiotic resistance intestinal Escherichia coli collected from practitioners in dietary services area to analyse the incidence, epidemiology of phonotype and genotye of Extended-spectrumβ-lactamase producing Escherichia coli in order to provide reference for prevention and treatment of drug-resistant.Methods: Intestinal Escherichia coli of practitioners collected in dietary services area from March to July in 2006 were tested for resistance to antibiotics by Agar dilution and exrtraintestinalpathogenic Escherichia coli from patient simultaneously collected from 5 hospitals. ESBLs producing strains screening test was performed by substrates Ceftriaxone, Ceftazidime,Cefotaxime,Aztreonam with a final concentration of 1μg/ml and ESBLs producing strains phenotype confirmation test was performed by broth microdilution. Through the whole experiments the international standard strains of Escherichia coli ATCC 25922(non-ESBLs producing strain) and pneumonia Klebsiella ATCC700603 (ESBL-producing strain) were refered as negative and positive control. The PCR method was used to amplify blaSHV and blaCTX-M through two pairs of conserved primers. To distinguish the sub-genotype of ESBLs CTX-M PCR products were digested with restriction endonucleases PstⅠand PvuⅡthen analysed by restriction fragment length polymorphism (RFLP). Results: The total of intestinal Escherichia coli collected from practitioners in dietary services area was 716 strains. Antibiotic sensitivity test shows that the highest level of antibiotic resistance rate was Penicillin which reach to 65.78%(471/716), the antibiotic resistance rate of aminoglycoside was 15.78%(153/716), the antibiotic resistance rate of first-generation quinolone was 37.15%(266/716), the antibiotic resistance rate of third-generation cephalosporins and third-generation quinolone were lower, 17.74%(127/716)and 5.39%(41/716). the multi-drug(resistant to 3 or more antibiotics) resistance rate of the strains was 33.79% (242/716).There was a significant difference between third-generation cephalosporins resistance and third-generation quinolone resistance (χ2=54.38,p<0.01), but there was no significant difference between third-generation cephalosporins resistance and aminoglycoside resistance (χ2=3.31,p>0.05). The incidence of ESBLs-producing Escherichia coli in intestinal Escherichia coli and exrtraintestinalpathogenic Escherichia coli was 2.51%(18/716) and 37.68%(102/716). 12.50%(13/120) of ESBLs producing Escherichia coli carried SHV gene,87.5% (105/120) carried CTX-M gene and 10.80% (13/120) carried CTX-M+SHV gene. There was 20.00%(21/105)CTX-M-1 subgroup, 2.86%(3/105) CTX-M-2 subgroup,77.14%(81/105) CTX-M-9 subgroup (CTX-M-14) in 105 CTX-M-ESBLs. The 120 ESBLs-producing Escherichia coli were all multi-drug resistant, the resistant rate of penicillin reached to 100% (120/120), to first-generation and second-generation cephalosporin resistance were more than 70%,to third-generation cephalosporins were about 60%, the antibiotic resistance rate of Gentamicin and Kanamycin were70.83%(85/120)and 69.16%(83/120), the antibiotic resistance rate of quinolone was about 60%, except the Nalidixic Acid rate 84.17%(101/120). Conclusion:(1)The hightest resistant level of Escherichia coli isolated from practitioners in dietary services area was to penicillin while the lowest were the third-generation cephalosporins and the third-generation quinolones. (2) There was a significant difference between third-generation cephalosporins resistance and third-generation quinolones resistance, but there was no significant difference between third-generation cephalosporins resistance and aminoglycoside resistance. (3)The incidence of ESBLs-producing Escherichia coli exrtraintestinalpathogenic in Fuzhou was at the same level with other cities in China but significent higher than the incidence of ESBLs-producing Escherichia coli from intestinal Escherichia coli in Fuzhou.(4)The main genotype was CTX-M, the others was SHV and CTX-M+SHV gene. They have been seriously threatening the local anti-infection treatment so we should closely monitor their transmention. (5)We used PCR-RFLP to analyse the CTX-M subgroup, the main CTX-M subgroup in Fuzhou area was CTX-M -9 subgroup(CTX-M-14), meanwhile there were CTX-M-1 and CTX-M-2 subgroup.the subgroups were different from other places in and out of china. The PCR-RFLP is a quick and accurate way to analyse the subgroup of blaCTX-M.