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Diagn Microbiol Infect Dis. 2019 Aug;94(4):365-370. doi: 10.1016/j.diagmicrobio.2019.02.008. Epub 2019 Feb 21.

Detection of Mycobacterium tuberculosis in paucibacillary sputum: performances of the Xpert MTB/RIF ultra compared to the Xpert MTB/RIF, and IS6110 PCR.

Author information

1
Pathogenesis and Control of Chronic Infections, INSERM, EFS, Université de Montpellier, CHU de Montpellier, France.
2
UMR MIVEGEC IRD-CNRS-Université de Montpellier, centre IRD, Montpellier, CHU Montpellier, Montpellier, France.
3
PhyMedExp, INSERM U1046, CNRS UMR 9214, Université de Montpellier, CHU Montpellier, Montpellier, France.
4
Institut de Recherche en Infectiologie de Montpellier (IRIM), Université de Montpellier, INSERM, CNRS UMR9004, Montpellier, France.
5
Pathogenesis and Control of Chronic Infections, INSERM, EFS, Université de Montpellier, CHU de Montpellier, France. Electronic address: e-tuaillon@chu-montpellier.fr.

Abstract

The Xpert MTB/RIF Ultra assay has recently been launched to improve the detection of smear negative disease. This retrospective study compares the sensitivity of Xpert MTB/RIF Ultra with that of Xpert MTB/RIF tests and IS6110 real-time PCR in sputum. Diagnostic performance of three molecular tests was evaluated using 48 culture-positive clinical respiratory specimens diluted to obtain paucibacillary sputum specimens. Xpert MTB/RIF Ultra had the highest sensitivity of 100% compared to 42% (P < 0.001) for Xpert MTB/RIF and 64.5% (P = 0.02) for IS6110-PCR. All "very low" or "low" positive specimens using Xpert MTB/RIF Ultra were tested positive using IS6110-PCR, but 35.4% were found negative using Xpert MTB/RIF. Xpert MTB/RIF Ultra is more sensitive than the two other tests for sputum with a low bacterial load. Adding detection of IS6110 and IS1081 to rpoB, is a key evolution of the assay and improves the detection of Mycobacterium tuberculosis' DNA in paucibacillary sputum.

KEYWORDS:

Chelex®; IS6110-PCR; Mycobacterium tuberculosis; Paucibacillary sputum; Xpert MTB/RIF; Xpert MTB/RIF ultra

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