[Evaluation of the discrepant Mycobacterium tuberculosis strains between any ordinary susceptibility testing and rpoB gene analysis by the line probe assay].
OBJECTIVE
Evaluation of rifampicin-resistance by the line probe assay, for rifampicin-susceptible Mycobacterium tuberculosis strains which were classified as rifampicin-resistant by the phenotypic drug susceptibility testings.


METHODS
A total of 15 clinical isolates from NHO Kinki-chuo Chest Medical Center consisting of 6 rifampicin-resistant strains by the line probe assay despite susceptible result by the drug susceptibility testings, and 9 clinical isolates which showed the fluctuating results on repeated drug susceptibility testings. After we conducted 3 drug susceptibility testings and the line probe assay, we have examined the sequence analysis for confirming mutations in the rpoB gene.


RESULTS
All strains were determined rifampicin-susceptible or intermediate by the drug susceptibility testings with Minimum Inhibitory Concentration (MIC) which ranged from 0.25 to 4 microg/ml by BrothMIC MTB-1, whereas these isolates indicated rifampicin-resistance by the line probe assay and revealed mutations in the hot-spot region (69 bp) by the sequence analysis.


CONCLUSIONS
We verified that the line probe assay might be useful for the correct determination of drug susceptibility, especially about the low-level rifampicin-resistant M. tuberculosis strains.
Yoshida
Shiomi
S
Clinical Research Center, National Hospital Organization Kinki-chuo Chest Medical Center, 1180 Nagasone-cho, Kita-ku, Sakai-shi, Osaka 591-8555, Japan. dustin@kch.hosp.go.jp
Suzuki
Katsuhiro
K
Tsuyuguchi
Kazunari
K
Tomita
Motohisa
M
Okada
Masaji
M
Sakatani
Mitsunori
M
D001426:Bacterial Proteins / Q000235:genetics*; D012321:DNA-Directed RNA Polymerases; D008826:Microbial Sensitivity Tests; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000302:isolation & purification; D012293:Rifampin / Q000494:pharmacology*
D001426:Bacterial Proteins; C505805:rpoB protein, Mycobacterium tuberculosis; D012321:DNA-Directed RNA Polymerases; D012293:Rifampin