A total of 870 Mycobacterium tuberculosis isolates composed of sputum and bronchoalveolar lavage fluid were collected from patients with pulmonary tuberculosis (PTB) in the Affiliated Hospital of Zunyi Medical College during the years of 2013 to 2016. Drug sensitivity tests against 4 anti-TB drugs (rifampicin, isoniazid, ethambutol and streptomycin) were performed using the Roche culture and proportion method. The demographic and drug resistance information were collected.

Among the 870 cases, 611 cases were new patients and 259 cases were previously treated patients. The total rates of drug resistant and multidrug-resistant (MDR) were 26.6% (231/870) and 12.1% (105/870),respectively. The total drug resistant rates of new and previously treated patients were 16.4% (100/611) and 50.6% (131/259),respectively, and the difference was statistically significant (χ ²=56.74,P<0.01). The single drug resistance rates of new and previously treated patients were 9.7% (59/611) and 10.0% (26/259), respectively, and the difference was not statistically significant (χ ²=0.03, P=0.862). The polyresistance rates of new and previously treated patients were 3.1% (19/611) and 8.5% (22/259),respectively. The difference was statistically significant (χ ²=11.74, P<0.01). The MDR rates of new and previously treated patients were 3.6% (22/611) and 32.0% (83/259), respectively. And the difference was statistically significant (χ ²=138.69, P<0.01).

Retreatment would increase the risk of TB’s resis-tance to drugs. Consequently, there is a urgent call for the improvement of drug resistance screening and standar-dized treatment for retreated PTB patients.