DNA extracted from stained sputum smears can be used in the MTBDRplus assay

We examined the feasibility of using DNA extracted from stained sputum smears for the detection of rifampin and isoniazid resistance with the commercial MTBDRplus assay from Hain Lifescience GmbH, Nehren, Germany. Overall sensitivity was initially low (70.0%) but increased to 96.7% when a multiplex PCR preamplification step was added. We then tested stored Mycobacterium tuberculosis-positive stained smears prepared from 297 patients' sputum samples. Species identification and drug susceptibility testing (DST) had been performed at the Institut Pasteur de Madagascar. Overall, the performance of the MTBDRplus assay applied to slide DNA was similar to that obtained in other studies with DNA extracted from clinical specimens. With the ready availability of stained smears in routine diagnostic laboratories and their easy transport and storage at room temperature, this approach should be useful for optimizing the treatment of multidrug-resistant tuberculosis and for conducting resistance surveys aimed at identifying hot-spot regions and breaking chains of transmission.