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Open Access Highly Accessed Research article

Comparative evaluation of three immunochromatographic identification tests for culture confirmation of Mycobacterium tuberculosis complex

Kinuyo Chikamatsu1*, Akio Aono1, Hiroyuki Yamada1, Tetsuhiro Sugamoto1, Tomoko Kato12, Yuko Kazumi1, Kiyoko Tamai3, Hideji Yanagisawa3 and Satoshi Mitarai12

Author Affiliations

1 Department of Mycobacterium Reference and Research, Research Institute of Tuberculosis, Japan Anti-Tuberculosis Association, Kiyose, Tokyo 204-8533, Japan

2 Department of Basic Mycobacteriosis, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki 852-8501, Japan

3 Miroku Medical Laboratory Company Limited, 659-2 Innai, Saku, Nagano 384-2201, Japan

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BMC Infectious Diseases 2014, 14:54  doi:10.1186/1471-2334-14-54

Published: 1 February 2014

Abstract

Background

The rapid identification of acid-fast bacilli recovered from patient specimens as Mycobacterium tuberculosis complex (MTC) is critically important for accurate diagnosis and treatment. A thin-layer immunochromatographic (TLC) assay using anti-MPB64 or anti-MPT64 monoclonal antibodies was developed to discriminate between MTC and non-tuberculosis mycobacteria (NTM). Capilia TB-Neo, which is the improved version of Capilia TB, is recently developed and needs to be evaluated.

Methods

Capilia TB-Neo was evaluated by using reference strains including 96 Mycobacterium species (4 MTC and 92 NTM) and 3 other bacterial genera, and clinical isolates (500 MTC and 90 NTM isolates). M. tuberculosis isolates tested negative by Capilia TB-Neo were sequenced for mpt64 gene.

Results

Capilia TB-Neo showed 100% agreement to a subset of reference strains. Non-specific reaction to M. marinum was not observed. The sensitivity and specificity of Capilia TB-Neo to the clinical isolates were 99.4% (99.6% for M. tuberculosis, excluding M. bovis BCG) for clinical MTC isolates and 100% for NTM isolates tested, respectively. Two M. tuberculosis isolates tested negative by Capilia TB-Neo: one harbored a 63-bp deletion in the mpt64 gene and the other possessed a 3,659-bp deletion from Rv1977 to Rv1981c, a region including the entire mpt64 gene.

Conclusions

Capilia TB-Neo is a simple, rapid and highly sensitive test for identifying MTC, and showed better specificity than Capilia TB. However, Capilia TB-Neo still showed false-negative results with mpt64 mutations. The limitation should be recognized for clinical use.

Keywords:
Capilia TB-Neo; Mycobacterium tuberculosis complex identification; mpt64 gene