Molecular Epidemiology Study Of Extended-spectrum β-lactamases In Escherichia Coli And Klebsiella Pneumoniae Isolated From Lower Respiratory Tract

Objective To investigate the incidences, risk factors , drug resistances and the prevalence of genotypes of extended-spectrum β-lactamases in Escherichia coli and Klebsiella pneumoniae which were isolated from lower respiratory tract between Jan 2002 and Dec 2003 in Shenzhen People's Hospital.Methods A total of 127 strains of E.coli and K.pneumoniae were tested to drug susceptibility by agar diffusion. ESBLs were confirmed with inhibitor-potentiated test. Risk factors were studied rerospectively by case-control study,and data were analyzed by Chi-square test and unconditional Logistic regression.The MICs of 61 ESBLs -producing strains were tested by agar dilution. ESBLs genotypes were analyzed by PCR and nucleotide sequencing.Results The ESBLs positive rate of E.coli was 78.72%, K.pneumoniae was 57.50%. The drug resistance of positive ESBLs was higher than that of negative ESBLs to most drugs,and most of them were multiple-drug-resistances.The sensitive rates of imipinem and meropenem to ESBLs- producing strains were 100%. The independent risk factors were using oxyimino β -lactam antibiotics over three days, indwelling nasogastric tube and aerosol inhalation.There were altogether 10genotypes of β -lactamases in the 61 ESBLs- producing strains.CTX-M were83.6%, including 38 strains CTX-M-14; SHV were 44.3%, including 20strainsSHV-12, and all of them were found out in K.pneumoniae; TEM were37,7%, all of them were TEM-1. Conclusion This study shows that in Shenzhen People's Hospital, the prevalence of ESBLs was high in E.coli and K.pneumoniae isolated from lower respiratory tract. ESBLs-producing strain acquisition can attribute to multiple factors, mainly to using oxyimino β -lactam antibiotics, indwelling nasogastric tube and aerosol inhalation. CTX-M-type and SHV-type are predominant genotypes of ESBLs in E.coli and K.pneumoniae. Moreover, each kind of genotypes is different in E.coli and K.pneumoniae,which leads to differential resistances. The resistant rates of these bacteris are high, and the multiple-drug-resistances are very common. Carbopenems are the most effective antibiotics to deal with this kind of infections.