Objective To investigate the distribution and antibiotic resistance of pathogens isolated fromlower respiratory tract in mechanically ventilated patients with acute exacerbation of chronic obstructive pulmonary disease ( AECOPD) . Methods The patients with AECOPD, who were hospitalized in RICU from January 2008 to November 2009, were divided into a community infection group and a nosocomial infection group. Lower respiratory tract isolates were collected by bronchoscopic protected specimen brush for bacterial identification and susceptibility test. Results 134 cases were enrolled in the study, with 75 cases in thecommunity infection group and 59 cases in the nosocomial infection group. The positive detection rate in the nosocomial infection group was significantly higher than that in the community infection group [ 81. 4%( 48/59) vs. 54. 7% ( 41/75) ] . In the community infection group, 49 strains were isolated, in which gramnegativebacteria, gram-positive bacteria, and fungi accounted for 55. 1% , 28. 6% , and 16. 3% , respectively.In the nosocomial infection group, 55 strains were isolated, in which gram-negative bacteria, gram-positive bacteria, and fungi accounted for 61. 8% , 21. 8% , and 16. 4%, respectively. There was no significant difference in the microbial distribution between the two groups ( P gt; 0. 05) . The detection rate of ESBLs producing strains in the nosocomial infection group was significantly higher than that in the community infection group ( 58. 8% vs. 37% ) . The resistance rates in the nosocomial groups were higher than those in the community infection group. Conclusions Antibiotic resistance is serious in mechanically ventilated patients with AECOPD, especially in the nosocomial infection patients. The increased fungi infection and drug resistance warrant clinicians to pay more attention to rational use of antibiotics, and take effective control measures.