Antibiotic Risitance, Genotype Distribution And Clinical Risk Factors Of Extended-spectrum β-lactamases Produced By Escherichia Coli And Klebsiella Pneumoniae Isolated From The Patients With Lower Respiratory Tract Infection

Objective:To investigate the prevalence,resistance,genotypes and the clinical risk factors of extended-spectrumβ-lactamases produced by Escherichia coli and Klebsiella pneumoniae isolated from the patients with lower respiratory tract infection in THE FIRST AFFILIATED HOSPITAL OF GUANGXI MEDICAL UNIVERSITY.Methods:K-B disk diffusion method was used in susceptibility testing and ESBLs producers were detected by NCCLS Phenotypic Confirmatory Test(disk diffusion test)in 154 strains of Escherichia coli and Klebsiella pneumoniae collected from lower respiratory tract phlegm-samples during Jan.2006 to June. 2006.Theβ-lactamases genes of 32 strains among the 154 ESBLs-producing strains were identified by PCR,and the 32 corresponding clinical cases caused by positive- ESBLs strains were studied as the test group,with 30 clinical cases caused by negative- ESBLs strains as the control group with the corresponding hospitalization in the same hospital.Datas of the risk factors were analyzed by multivariate logistic regression.Result:(1)The prevalence of ESBLs-producers were 38.96%;The prevalence of Escherichia coli and Klebsiella pneumoniae were 60.94%and 23.33%.(2)The sensitive rates of ESBLs-producing strains to Piperacillin,Cefazolin,Cefotaxime, Ceftazidim,Cefepime and Aztreonam were 0%,4.8%,5%,70%,58.3 and 36.7% respectively.The sensitive rates to Piperacillin/Tazobactam and Cefoperazone/ Sulbactam were 78.3%and 71.7%.The resitance rate to Imipenem was 0%.(3)25 out of the 32 ESBLs-producing strains produced bla(CTX-M)gene(78.13%),9 strains produced bla(SHV)gene(28.13%),14 strains produced bla(TEM) gene(43.75%).The CTX-M-type was the most common genotype in Escherichia coli and so was the SHV -type in Klebsiella pneumoniae.15 out of the 32 test samples carried two or three genotypes of ESBLs(46.86%),and the rate of Escherichia coli and Klebsiella pneumoniae were 45.46%and 50%. (4)Multivariate logistic regression analysis showed that the independent risk factors of the the patients with the infection of the ESBLs-producing strains in lower respiratory tract were the course of hospitalization,invasive operations for diagnosis and treatments and the third or forth generation cephalosporins administration;The last one was the most important risk factor.The odds ratio were 3.575,8.847,15.121 respectively.Conclusion:(1)The ESBLs producers were commonly found in Escherichia coli and Klebsiella pneumoniae isolated from the patients with lower respiratory tract infection from our hospital.(2)Most of them are multiantibiotic resistant.(3)CTX-M-type was the main genotype of ESBLs in our hospital;The CTX-M-type was the main genotype in Escherichia coli and so was the SHV-type in Klebsiella pneumoniae.The ESBLs-producing strains usually carried two or three genotypes of ESBLs.(4)The infection of the ESBLs-producing strains in lower respiratory tract was caused by multiple factors,and mianly related to the course of hospitalization,invasive operations for diagnosis and treatments and the third or forth generation cephalosporins administration.