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Diagnostic Evaluation of Non-Interpretable Results Associated with rpoB Gene in Genotype MTBDRplus Ver 2.0

Tuberculosis and Respiratory Diseases 2020년 83권 4호 p.289 ~ 294
Singh Binit Kumar, Sharma Rohini, Kodan Parul, Soneja Manish, Jorwal Pankaj, Nischal Neeraj, Biswas Ashutosh, Sarin Sanjay, Ramachandran Ranjani, Wig Naveet,
소속 상세정보
 ( Singh Binit Kumar ) - All India Institute of Medical Sciences Department of Medicine
 ( Sharma Rohini ) - All India Institute of Medical Sciences Department of Medicine
 ( Kodan Parul ) - All India Institute of Medical Sciences Department of Medicine
 ( Soneja Manish ) - All India Institute of Medical Sciences Department of Medicine
 ( Jorwal Pankaj ) - All India Institute of Medical Sciences Department of Medicine
 ( Nischal Neeraj ) - All India Institute of Medical Sciences Department of Medicine
 ( Biswas Ashutosh ) - All India Institute of Medical Sciences Department of Medicine
 ( Sarin Sanjay ) - Foundation for Innovative New Diagnostics
 ( Ramachandran Ranjani ) - World Health Organization
 ( Wig Naveet ) - All India Institute of Medical Sciences Department of Medicine

Abstract


Background: Line probe assay (LPA) is standard diagnostic tool to detect multidrug resistant tuberculosis. Non-interpretable (NI) results in LPA (complete missing or light wild-type 3 and 8 bands with no mutation band in rpoB gene region) poses a diagnostic challenge.

Methods: Sputum samples obtained between October 2016 and July 2017 at the Intermediate Reference Laboratory, All India Institute of Medical Sciences Hospital, New Delhi, India were screened. Smear-positive and smear-negative culture-positive specimens were subjected to LPA Genotype MTBDRplus Ver 2.0. Smear-negative with culture-negative and culture contamination were excluded. LPA NI samples were subjected to phenotypic drug susceptibility testing (pDST) using MGIT-960 and sequencing.

Results: A total of 1,614 sputum specimens were screened and 1,340 were included for the study (smear-positive [n=1,188] and smear-negative culture-positive [n=152]). LPA demonstrated 1,306 (97.5%) valid results with TUB (Mycobacterium tuberculosis) band, 24 (1.8%) NI, three (0.2%) valid results without TUB band, and seven (0.5%) invalid results. Among the NI results, 22 isolates (91.7%) were found to be rifampicin (RIF) resistant and two (8.3%) were RIF sensitive in the pDST. Sequencing revealed that rpoB mutations were noted in all 22 cases with RIF resistance, whereas the remaining two cases had wild-type strains. Of the 22 cases with rpoB mutations, the most frequent mutation was S531W (n=10, 45.5%), followed by S531F (n=6, 27.2%), L530P (n=2, 9.1%), A532V (n=2, 9.1%), and L533P (n=2, 9.1%).

Conclusion: The present study showed that the results of the Genotype MTBDRplus assay were NI in a small proportion of isolates. pDST and rpoB sequencing were useful in elucidating the cause and clinical meaning of the NI results.

키워드

Mycobacterium tuberculosis Complex; Line Probe Assay; Drug Susceptibility Testing; Sequencing

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