Abstract: Objective: To investigate the distribution and drug resistance of bacteria causing lower respiratory tract infection in senile patients in department of respiratory diseases,and study the prevalence of the bacteria producing extended-spectrum β-lactamases(ESBLs) in Escherichia coli and Klebsiella pneumoniae.Methods: The specimen of sputum was tested by culture to inspect pathogens.Kirby-Bauer agar diffusion method was used to judge drug sensitivity.Phenotypic confirmatory test was used to detect ESBLS.Results: A total of 521 strains were obtained from specimen of 2 177 sputum.Among which 389 strains were Gram-negative bacilli,81 strains were Gram-positive coccus,51 strains were fungus.The predominant pathogens in Gram-negative bacilli were Acinetobacter baumanii and Klebsiella pneumoniae,and showed high resistance to common antibiotics.The total percentage of ESBLsproducing was 23.3%,in which Escherichia coli was 19.1%,and Klebsiella pneumoniae was 26.0%.Conclusions: The Gram-nagative bacilli was the major pathogens isolated from senile patients with lower respiratory tract infection in department of respiratory diseases,and it has markedly increased resistance to common antibiotics.The monitoring for pathogens and drug sensitivity should be enhanced to give clinicians suggestion for rational use of antibiotics.