Antibiotic Resistance Of ESBLs-producing Bacterium In Children With Respiratory Tract Infection And Resistant Activity Analysis Of Gene Recombinant Strain

BackgroundRespiratory infection is common and frequent in children, bacterium are importantlyinfectious agent. β-Lactam antibilotics are preferred anti-infection drugs inpaediatrics.Under their pressure, bacterium produce ESBLs gradually. ESBLs-producingbacterium have many kinds of genotype of drug resistance and show resistant to manyantibilotics,which brings difficulty to anti-infection treatment.The distribution of bacterial strain、drug resistance gene and resistant activity ofESBLs-producing bacterium is varied in different country、 district and period.Atpresent,there are more than700kinds of drug resistance genotype in ESBLs-producingbacterium, including TEM, SHV, CTX-M and other genotype. CTX-M has beendominating genotype instead of TEM and SHV in whole globe since2000. The maincharacteristic of antimicrobial resistance of CTX-M-producing bacterium is sentitive to Ceftazidime and resistant to Cefotaxime. How to treat infection of CTX-M-producingbacterium effectively is urgent problem in clinic.Objectives1. To investigate the resistant phenotype of ESBLs-producing bacterium in childrenwith respiratory tract infection.2. To investigate the resistant genotype of ESBLs-producing bacterium in children withrespiratory tract infection.3. To determine the resistant activity of mainly prevalent ESBLs.Methods1. Collect ESBLs-producing bacterium isolated in children with respiratory tractinfection from Jul.2011to Oct.2012, susceptibility test against antibiotics wasperformed by K-B slip of paper diffusion process.2. Design primer of primary drug resistance gene,including TEM, SHV, CTX-M-1,CTX-M-2and CTX-M-9, PCR method was employed to detect the primarygenotype of ESBLs-producing bacterium,and the mainly prevalent gene wasdetected by DNA sequencing.3. Using gene recombination technology to construct the expressing vector of mainlyprevalent genotype, using CaCl2transforming method to introduce the expressingvector of recombinant gene into E.coli BL21, prokaryotic expression was inducedby IPTG, and at last susceptibility test against antibiotics of the mainly prevalentESBLs was carried out by K-B slip of paper diffusion process.Results1.47strains of ESBLs-producing bacterium were isolated from children withrespiratory tract infection, the main bacterium included26strains of Escherichia coliand21strains of Klebsiella pneumoniae，(the rates of enzyme production were52%and47.7%respectively). ESBLs-producing bacterium were highly resistant tocephalosporin,(the resistant rates to Ceftazidime, Cefuroxime, ceftriaxone all were100%), partly resistant to Cefepime (the resistant rates were between26.9%and38.1%), there were differences in the resistance to β-lactamasesantibiotics/inhibitor Ampicillin/salbactam, efoperazone/sulbactam, Piperacillin/Tazobactam), theresistant rate to imipenem and meropenem was0%.2. The genotype of drug resistance included TEM (positive detection rate was29.8%),SHV (positive detection rate was10.6%), CTX-M-1group (positive detection ratewas21.3%), CTX-M-9group (positive detection rate was51.1%), and CTX-M-14was mainly prevalent genotype by DNA sequencing.3. Successfully construct the expressing vector of recombinant gene and express theenzyme of CTX-M-14. According to the K-B slip of paper diffusion process,CTX-M-14was resistant to Ceftriaxone、Cefuroxime and Cefotaxime，was sensitiveto Cefepime、 Ceftazidime、 β-lactamasesantibiotics/inhibitor、 imipenem andmeropenem.ConclusionsESBLs-producing bacteria has the phenotype of multiple-drug resistance，which ishighly resistant to cephalosporin, partly susceptible to inhibitor of β-lactamasesantibiotics, only fully susceptible to Carbapenems. The phenotype of multiple-drugresistance is due to the multiple-drug resistance gene mediated by plasmid. So theresearch is very important in curing ESBLs-producing bacterium in children withrespiratory tract infection reasonably and effectively.