title: Evaluation of the speed-oligo direct Mycobacterium tuberculosis assay for molecular detection of mycobacteria in clinical respiratory specimens.
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.
authors.affiliation: Department of Microbiology, University Hospital Virgen de las Nieves, Granada, Spain.
authors.forename: Ana
authors.initials: A
authors.lastname: Lara-Oya
authors.forename: Pablo
authors.initials: P
authors.lastname: Mendoza-Lopez
authors.forename: Javier
authors.initials: J
authors.lastname: Rodriguez-Granger
authors.forename: Ana María
authors.initials: AM
authors.lastname: Fernández-Sánchez
authors.forename: María Pilar
authors.initials: MP
authors.lastname: Bermúdez-Ruiz
authors.forename: Inmaculada
authors.initials: I
authors.lastname: Toro-Peinado
authors.forename: Begoña
authors.initials: B
authors.lastname: Palop-Borrás
authors.forename: Jose María
authors.initials: JM
authors.lastname: Navarro-Marí
authors.forename: Miguel José
authors.initials: MJ
authors.lastname: Martínez-Lirola
mesh_terms: D001431:Bacteriological Techniques / Q000379:methods*; D006801:Humans; D025202:Molecular Diagnostic Techniques / Q000379:methods*; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000302:isolation & purification*; D009841:Oligonucleotides; D012680:Sensitivity and Specificity; D013183:Sputum / Q000382:microbiology*; D013997:Time Factors; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis*
chemical_list: D009841:Oligonucleotides