Rapid detection of Mycobacterium tuberculosis complex and rifampin resistance in smear-negative clinical samples by use of an integrated real-time PCR method

Sixty-four of 85 (75.3%) smear-negative respiratory (n 78) and nonrespiratory (n 7) samples with positive cultures of Mycobacterium tuberculosis complex (MTC) were detected by the GeneXpert system using the Xpert MTB/RIF assay (GX). In addition, GX found rpoB mutations in all six of the rifampin-resistant strains detected. The test was negative in 20 culture-negative and 20 nontuberculous culture-positive samples (100 % specificity). GX offers high potential for the diagnosis of tuberculosis due to its capacity for direct detection of MTC, its rapidity, and its simplicity. Tuberculosis (TB) remains one of the biggest health prob-lems in developing and industrialized countries and is asso-ciated with high rates of morbidity and mortality (19). The emergence and spread of Mycobacterium tuberculosis strains resistant to multiple drugs represent a serious threat to TB control worldwide (18). Early diagnosis of active TB and de-tection of multidrug-resistant (MDR) strains are essential to interrupt transmission. Traditionally, acid-fast bacillus (AFB) smear microscopy has been the initial method for diagnosis