Abstract: Objective To investigate the distribution and drug resistance of pathogens in elderly multidrug-resistant pulmonary tuberculosis (MDR-TB) patients with lower respiratory tract infection, and to guide rational clinical therapy. Methods From January 2007 to January 2011, 83 elderly multidrug-resistant pulmonary tuberculosis patients were registered in the hospital, among which 44 sputum culture-positive cases with lower respiratory tract infection were enrolled as elderly group. There were 153 young and middle-aged (older than 18 years and younger than 60 years old) sputum culture-positive multidrug-resistant pulmonary tuberculosis patients with lower respiratory tract infection during the same period, 50 cases selected according to the registered number were enrolled as control group. All patients were examined for sputum culture, bacterial identification and susceptibility test. The data retrieved from the two groups were compared using cohort analysis. Comparisons of categorical variables were performed using the Pearson Chi-square tests or Fisher’s exact tests. Statistical significance was set as P<0.05. Results A total of 54 pathogenic bacteria strains were isolated from sputum samples retrieved from 44 cases of elder multidrug-resistant pulmonary tuberculosis with lower respiratory tract infection. Among them, the proportion of gram-negative bacillus was in the first place, accounting for 53.70% (29/54),compared with the control group (66.10%, 39/59), there was no significant difference (χ²=1.808, P>0.05). The second was fungi at the percentage of 42.59% (23/54), compared with the young and middle-aged multidrug-resistant pulmonary tuberculosis patients (30.51%,18/59), there was no statistically significant difference(χ²=1.781, P>0.05).The proportion of gram-positive bacteria accounted for 3.70% (2/54) in elderly group and 3.39% (2/59) in control group, without statistically significant difference (Fisher’s exact test; P>0.05). Mixed infection rate was 22.72% (10/44) in elderly group, which was higher than that of the control group (18.00%, 9/50) (χ²=0.215,P>0.05). The drug susceptibility test (DST) of gram-negative bacteria showed that there was statistically significant difference between the two groups. Moreover, the sensitivity rates to amikacin (100.00%,29/29), gentamycin (65.52%, 19/29) and cefazolin (58.62%,17/29) in the elderly group were significantly higher than those in the control group (41.03% (16/39), 33.33% (13/39) and 12.82% (5/39) respectively (χ²=25.844,6.915,15.941,all P<0.05). Conclusion The primary pathogenic bacteria of lower respiratory tract infection in the elderly MDR-TB patients were gram-negative pathogen, and the mixed infection rate was high. In clinical settings, attention should be paid to bacterial culture and drug sensitivity test in order to reduce improper use of the antibiotics.