Use of a Molecular Diagnostic Test in AFB Smear Positive Tuberculosis Suspects Greatly Reduces Time to Detection of Multidrug Resistant Tuberculosis

Background: The WHO has recommended the implementation of rapid diagnostic tests to detect and help combat M/XDR tuberculosis (TB). There are limited data on the performance and impact of these tests in field settings. Methods: The performance of the commercially available Genotype MTBDRplus molecular assay was compared to conventional methods including AFB smear, culture and drug susceptibility testing (DST) using both an absolute concentration method on Löwenstein-Jensen media and broth-based method using the MGIT 960 system. Sputum specimens were obtained from TB suspects in the country of Georgia who received care through the National TB Program. Results: Among 500 AFB smear-positive sputum specimens, 458 (91.6%) had both a positive sputum culture for Mycobacterium tuberculosis and a valid MTBDRplus assay result. The MTBDRplus assay detected isoniazid (INH) resistanc

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