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Evaluation of GeneXpert MTB/RIF for the detection of Mycobacterium tuberculosis and resistance to rifampin in clinical specimens

Authors
  • Bunsow, Eleonora
  • Ruiz-Serrano, María Jesús
  • López Roa, Paula
  • Kestler, Martha
  • Viedma, Dario Garcia
  • Bouza, Emilio1, 2, 3, 4, 5
  • 1 Department of Clinical Microbiology and Infectious Diseases
  • 2 Hospital General Universitario Gregorio Marañón
  • 3 Facultad de Medicina
  • 4 Universidad Complutense de Madrid
  • 5 CIBER de Enfermedades Respiratorias (CIBERES)
Type
Published Article
Journal
Journal of Infection
Publisher
Elsevier
Publication Date
Jan 01, 2013
Accepted Date
Nov 21, 2013
Volume
68
Issue
4
Pages
338–343
Identifiers
DOI: 10.1016/j.jinf.2013.11.012
Source
Elsevier
Keywords
License
Unknown

Abstract

ObjectivesGeneXpert (GX) is a novel real-time polymerase chain reaction assay for the simultaneous detection of Mycobacterium tuberculosis (MTB) and resistance to rifampin (RIF). We evaluated the performance of GX for direct detection of MTB in respiratory and non-respiratory specimens and assessed the ability of the assay to detect resistance to RIF in non-tuberculosis (TB) endemic country. MethodsWe analyzed 595 clinical samples in a 1550-bed tertiary hospital in Madrid, Spain. Specimens were processed using GX, auramine smear, conventional culture, and drug phenotypic susceptibility testing (DST) with MGIT SIRE (BD). ResultsOf the 595 clinical samples, 305 (51.3%) were non-respiratory and 290 (48.7%) were respiratory. In total, MTB was isolated in 81 specimens, 71 of which were positive with GX. The sensitivity, specificity, PPV, and NPV of the GX were: 97.1%, 98.6%, 95.7% and 99.1% for respiratory samples and 33.3%, 99.7%, 80.0% and 97.3% for non-respiratory. GX detected 8 RIF-resistant samples, but only 5 were confirmed by DST. ConclusionsGX is an accurate, easy-to-apply and rapid test to detect MTB, especially in smear-positive respiratory samples. Although is a useful tool for the rapid identification of RIF-resistant MTB strains, the rifampin resistant results should be confirmed by DST.

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