Characterization of a 411-bp fragment of the rpoB gene in clinical isolates of Mycobacterium tuberculosis in a university hospital in northern Taiwan.

Background and Purpose: This study analyzed rpoB gene mutation and its correlation with demographic and clinical data, and the drug resistance profile in 41 consecutive patients with rifampin (RIF)-resistant Mycobacterium tuberculosis isolated at National Taiwan University Hospital from 2000 to 2002. Methods: The 411-bp fragment of the rpoB gene from 94 M. tuberculosis isolates (including 41 RIF-resistant and 53 RIF-susceptible isolates) was amplified and sequenced. Results: Of the 41 RIF-resistant isolates, 87.8% (36/41) showed mutations in rpoB. The following mutations were identified: Ser(531) (68.3%), His(526) (9.8%), Ser(522) (4.9%) and Gln(513) (4.9%). No silent substitutions were observed. No mutation within the. entire 411-bp fragment was found in 12.2% (5/41) of the RIF-resistant isolates and 100% (53/53) of the RIF-susceptible isolates, Patients whose RIF-resistant isolates did not have rpoB mutation had higher frequencies of the following characiteristics: elderly, no previous history of tuberculosis, human immunodeficiency virus-negative, no extrapulmonary tuberculosis involvement and favorable prognosis. Drug resistance patterns in RIF-resistant M. tuberculosis strains were significantly correlated with isoniazid resistance, i.e., multidrug-resistant strains (90.2%). Conclusions: RIF-resistant M. tuberculosis isolates with rpoB mutation were clustered in the 69-bp core region in this study. Rapid detection of RIF resistance could be achieved by testing for rpoB mutation in Taiwan.