Sequencing of the pncA Gene in Members of the Mycobacterium tuberculosis Complex Has Important Diagnostic Applications: Identification of a Species-Specific pncA Mutation in “Mycobacterium canettii” and the Reliable and Rapid Predictor of Pyrazinamide Resistance

Testing for susceptibility to pyrazinamide (PZA) and analysis of the pncA gene sequences of 423 Mycobacterium tuberculosis complex isolates have revealed a unique silent nucleotide substitution that enables the rapid identification of “M. canettii” (proposed name). Moreover, the lack of a defined mutation within the pncA gene strongly suggests that an alternative mechanism is responsible for PZA resistance. Our results indicate that DNA sequencing of the pncA gene has the potential to shorten the turnaround time and increase the accuracy of PZA susceptibility testing of the M. tuberculosis complex. The Mycobacterium tuberculosis complex (MTB complex) consists of the closely related organisms M. tuberculosis, M. africanum, M. bovis, M. bovis BCG, M. caprae, M. microti, M. pinnipedii, the dassie bacillus, and “M. canettii” (proposed name) (3, 5, 6, 26). Although the members of the complex may differ in their epidemiologies, host spectra, geographic ranges, pathogenicities, and antituberculosis drug susceptibilities and although they display different phenotypic characteristics by conventional biochemical tests, they show high degrees of genetic homogeneity (10, 25). Conventional phenotypic methods for the identification of the members of the MTB complex are laborious and timeconsuming, and they require a large biomass (13). Thus, molecular methods (such as DNA sequencing of the oxyR, pncA, gyrB ,o rhsp65 gene; analysis of spacers between direct repeats in the direct repeat region; and deletion analysis of the regions of difference [RD]) provide a more rapid and accurate approach to the differentiation of the members of the MTB complex (8, 9, 16, 23, 24).