Distribution And Property Of Resistance Of CTX-M-Type ESBLs-producing Escherichia Coli Isolated From Bengbu Area

Objective:To investigate the CTX-M type of extended-spectrumβ-lactamases and ampC co-extistence in clinical isolates ESBLs-producing Escherichia coli in Bengbu.To study the resistance of the CTX-M-producing Escherichia coli strains against 13 antibiotics,and offer the resistance data to clinical reasonable therapy.Materials and Methods:Isolates:36 strains of ESBLs-producing Escherichia coli were collected between October in 2005 and June in 2006 from the First Affiliated Hospital of Bengbu Medical College,27 strains of ESBLs-producing Escherichia coli isolated from Bengbu area in the same period were provided by Anhui Center for Surveillance of Bacterial Resistance.Methods:Adopting PCR methods,genotypes of ESBLs and AmpC were determined with universal primers of bla_CTX-M,bla_TEM,bla_SHV and ampC.Agar dilution method was used to determine MICs of 13 antibiotics against Escherichia coli.Results:Positive amplification results were observed for 31 ESBLs-producing E.coli isolates which expressing CTX-M phenotype.The percentage of CTX-M-producing isolates in all ESBLs positive strains was 86.11%.4 and 5 strains were OXA and SHV,respectively.32 strains were TEM type ESBLs.The percentage was 88.89%.Positive amplification results weren't observed for AmpC. 11 and 26 strains were confirmed positive for CTX-M-1 group and CTX-M-9 group entire coding gene primers,respectively.Of 6 strains was positive for the both group primers.No strain was positive for CTX-M-2 group,CTX-M-8 group and CTX-M-25 group.4 strains were confirmed positive for OXA-1.Tow genotypes and more were observed for 28 strains.31 CTX-M⁺ strains were generally sensitive to carbopenems and piperacillin/tazobatan, while no strain was susceptible to piperacillin and quinolones.The results of MIC showed that there were higher resistance to ceftaxime and ceftriaxone.The rate of resistance to other third,fourth cephalosporins and cefoxitin was between 45.16%and 64.52%.Conclusions:CTX-M and TEM enzyme-producing strains were the most common in ESBLs-producing E.coli in the First Affiliated Hospital of Bengbu Medical College,some strains could produce SHV and OXA genotype ESBLs.The different genotypes could co-exist in a strain.