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Evaluation of GeneXPERT MTB/RIF assay in respiratory and non-respiratory specimens for the rapid detection of Mycobacterium tuberculosis

Abstract number: P2010

Archontakis Z., Dimoulas C., Charitakis A., Kanaki S., Foyntoylakis S., Michailellis E., Thymaki K., Liakou V.

Objectives: The principle of the Xpert MTB/RIF test running on GeneXpert system, is to detect M. tuberculosis complex (MTBC) and mutations in the gene rpoB that cause resistance to rifampicin. The aim of this study is to compare the detection sensitivity of pulmonary and extrapulmonary MTBC using MTB/RIF assay and GenoType MTBDRplus, (Hain Lifescience, Nehren, Germany) against liquid and solid culture (Becton Dickinson BACTEC™X MGIT™, Lowenstein-Jensen).

Methods: Each individual provided 3 sputum samples of sufficient quantity within 72 hours. Sputum samples for each patient were processed using NALC (n-acetylcysteine)/NaOH decontamination, were concentrated and tested using smear microscopy, culture, GenoType MTBDRplus and XpertMTB/RIF (smear and Xpert MTB/RIF were done from the same sediment as culture). Concentrated urine and gastric samples were centrifuged and up to 500 ml distilled water was added in the sediment prior to decontamination and addition of lysis buffer. Pleural fluids were not decontaminated but were centrifuged and up to 500 ml distilled water was added in the sediment before addition of lysis buffer. For liquid culture 500 ml of medium were centrifuged prior to addition of lysis buffer.

Results: 250 specimens have been tested. Culture was positive in 50 samples (Mean time of isolation 8.02 days). Twenty six (10.4%) were identified as atypical mycobacterium. None of these 26 samples were positive by the Xpert test. MTBC was isolated from 24 (9.6%) specimens, gastric fluids (n = 8), pleural fluids (n = 1), respiratory samples (n = 14) and urine (n = 1). All of these were positive by the Xpert MTB/RIF test. Twenty three specimens were identified as Mycobacterium tuberculosis and 1 (urine) was identified as Mycobacterium bovis (patient was known to be treated with M. bovis as immunotherapy for bladder cancer).

Conclusions: The Xpert MTB/RIF provides rapid and specific detection of MTBC compared with conventional laboratory tests, both in respiratory and extrapulmonary samples. It can be used as an important tool for early diagnosis of TB and efficient patient management.

Session Details

Date: 07/05/2011
Time: 00:00-00:00
Session name: Abstracts of 21st ECCMID / 27th ICC
Subject:
Location: Milan, Italy, 7 - 10 May 2011
Presentation type:
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