Eleonora Bunsow1, María Jesús Ruiz-Serrano2, Paula López Roa3, Martha Kestler3, Dario Garcia Viedma2, Emilio Bouza4. 1. Department of Clinical Microbiology and Infectious Diseases, Hospital General Universitario Gregorio Marañón, Doctor Esquerdo, 46, 28007 Madrid, Spain. Electronic address: eleonorabunsow@hotmail.com. 2. Department of Clinical Microbiology and Infectious Diseases, Hospital General Universitario Gregorio Marañón, Doctor Esquerdo, 46, 28007 Madrid, Spain; CIBER de Enfermedades Respiratorias (CIBERES), Spain. 3. Department of Clinical Microbiology and Infectious Diseases, Hospital General Universitario Gregorio Marañón, Doctor Esquerdo, 46, 28007 Madrid, Spain. 4. Department of Clinical Microbiology and Infectious Diseases, Hospital General Universitario Gregorio Marañón, Doctor Esquerdo, 46, 28007 Madrid, Spain; Facultad de Medicina, Universidad Complutense de Madrid, Spain; CIBER de Enfermedades Respiratorias (CIBERES), Spain.
Abstract
OBJECTIVES: GeneXpert (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. METHODS: We 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). RESULTS: Of 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. CONCLUSIONS: GX 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.
OBJECTIVES: GeneXpert (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. METHODS: We 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). RESULTS: Of 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. CONCLUSIONS:GX 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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