Evaluation of the Speed-oligo Direct Mycobacterium tuberculosis Assay for Molecular Detection of Mycobacteria in Clinical Respiratory Specimens |
| |
Authors: | Ana Lara-Oya Pablo Mendoza-Lopez Javier Rodriguez-Granger Ana María Fernández-Sánchez María Pilar Bermúdez-Ruiz Inmaculada Toro-Peinado Bego?a Palop-Borrás Jose María Navarro-Marí Miguel José Martínez-Lirola |
| |
Institution: | aDepartment of Microbiology, University Hospital Virgen de las Nieves, Granada, Spain ;bVircell S.L. Research, Santa Fé, Granada, Spain ;cDepartment of Microbiology, University Hospital Carlos Haya, Málaga, Spain ;dClinical Management Unit of Biotechnology, Torrecardenas Hospital Complex, Almería, Spain |
| |
Abstract: | We present the first evaluation of a novel molecular assay, the Speed-oligo Direct Mycobacterium tuberculosis (SO-DMT) assay, which is based on PCR combined with a dipstick for the detection of mycobacteria and the specific identification of M. tuberculosis complex (MTC) in respiratory specimens. A blind evaluation was carried out in two stages: first, under experimental conditions on convenience samples comprising 20 negative specimens, 44 smear- and culture-positive respiratory specimens, and 11 sputa inoculated with various mycobacterium-related organisms; and second, in the routine workflow of 566 fresh respiratory specimens (4.9% acid-fast bacillus AFB] smear positives, 7.6% MTC positives, and 1.8% nontuberculous mycobacteria NTM] culture positives) from two Mycobacterium laboratories. SO-DMT assay showed no reactivity in any of the mycobacterium-free specimens or in those with mycobacterium-related organisms. Compared to culture, the sensitivity in the selected smear-positive specimens was 0.91 (0.92 for MTC and 0.90 for NTM), and there was no molecular detection of NTM in a tuberculosis case or vice versa. With respect to culture and clinical data, the sensitivity, specificity, and positive and negative predictive values for the SO-DMT system in routine specimens were 0.76 (0.93 in smear positives 1.0 for MTC and 0.5 for NTM] and 0.56 in smear negatives 0.68 for MTC and 0.16 for NTM]), 0.99, 0.85 (1.00 in smear positives and 0.68 in smear negatives), and 0.97, respectively. Molecular misidentification of NTM cases occurred when testing 2 gastric aspirates from two children with clinically but not microbiologically confirmed lung tuberculosis. The SO-DMT assay appears to be a fast and easy alternative for detecting mycobacteria and differentiating MTC from NTM in smear-positive respiratory specimens. |
| |
Keywords: | |
|
|