Comparative evaluation of three immunochromatographic identification tests for culture confirmation of Mycobacterium tuberculosis complex.
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.
Department of Mycobacterium Reference and Research, Research Institute of Tuberculosis, Japan Anti-Tuberculosis Association, Kiyose, Tokyo 204-8533, Japan. chikamatsu@jata.or.jp.
Kinuyo
K
Chikamatsu
Akio
A
Aono
Hiroyuki
H
Yamada
Tetsuhiro
T
Sugamoto
Tomoko
T
Kato
Yuko
Y
Kazumi
Kiyoko
K
Tamai
Hideji
H
Yanagisawa
Satoshi
S
Mitarai
D001426:Bacterial Proteins / Q000235:genetics; D015373:Bacterial Typing Techniques / Q000379:methods*; D002846:Chromatography, Affinity / Q000379:methods*; D006801:Humans; D009169:Mycobacterium tuberculosis / Q000145:classification / Q000235:genetics / Q000254:growth & development / Q000302:isolation & purification*; D012680:Sensitivity and Specificity; D014376:Tuberculosis / Q000175:diagnosis / Q000382:microbiology*
D001426:Bacterial Proteins