Prospective evaluation of pyrosequencing for the rapid detection of isoniazid and rifampin resistance in clinical Mycobacterium tuberculosis isolates.

A pyrosequencing-based method for the rapid detection of isoniazid (INH) and rifampin (RIF) resistance in Mycobacterium tuberculosis was evaluated in clinical practice. The method can detect the INH resistance-causing katG315 mutation, and all mutations in the RIF resistance-determining rpoB core region, in less than 6 h from cultured isolates. The method was first validated with 42 isolates, and was subsequently prospectively evaluated with 91 isolates, including clinical isolates and external quality control assessment strains, over a period of 2.5 years. The pyrosequencing results of clinical isolates were available, on average, 19 days earlier (median 19 days; range 3-43 days) than conventional susceptibility testing results. The composite data showed that the sensitivity of pyrosequencing for detecting resistance correctly was 66.7% for INH and 97.4% for RIF. The specificity of pyrosequencing was 100% for both drugs. Acceptable sensitivity for detecting resistance and the rapidness of pyrosequencing make it a valuable tool in the clinical setting.