Résumé
BACKGROUND: Mycobacterium abscessus is the most pathogenic and drug-resistant rapid-growing mycobacterium. Clarithromycin or azithromycin are the only regular oral antimycobacterial agents that have an effect on M. abscessus. We tried to detect the clarithromycin-resistant strains from the clinical isolates of M. abscessus. METHODS: We tried to isolate the clarithromycin-resistant strains from 220 clinical isolates of M. abscessus by performing using reverse hybridization assay (RHA) and the broth microdilution test (BMT). RESULTS: Seven resistant strains (3.2%) from all the tested clinical isolates were detected by BMT. Three of these resistant strains were also detected by RHA and it was confirmed that they had point mutants. CONCLUSION: These results showed that clarithromycin resistance in M. abscessus clinical isolates is related to a point mutation and other unknown mechanisms.
Sujets)
Antibactériens , Azithromycine , Chimère , Clarithromycine , Mycobacterium , Mutation ponctuelleRésumé
BACKGROUND: Ethambutol (EMB) is one of important first-line drug in the treatment of tuberculosis. Molecular techniques to detect embB gene mutations have been considered as an method to define the EMB resistance. We investigated the mutation rate within embB gene among EMB resistant strains using reverse hybridization techniques. METHODS: We made 11 probes that had wild or mutated sequences containing codons 306, 406, or 497 within embB gene respectively. These probes were reverse-hybridized with PCR products amplified from embB gene which were isolated from 149 ethambutol resistant strains and 50 pan-susceptible strains. RESULTS: Out of 149 ethambutol resistant strains, one hundred (67.1%) had mutation at least one base at codon 306, 406, or 497 in embB gene. Mutation at codon 306, 406, 497 were demonstrated in 75 (50.3%), 16 (10.7%), and 13 strains (8.7%) respectively. There were four strains that showed multi-mutation at codon 306 and codon 406 simultaneously. A high proportion (8.1%) had single mutation at codon 406. There was no mutation observed in embB gene among 50 pan-susceptible strains. CONCLUSION: Reverse hybridization will be useful technique for detection of gene mutation correlated to ethambutol resistance.
Sujets)
Codon , Éthambutol , Génotype , Taux de mutation , Mycobacterium tuberculosis , Mycobacterium , Réaction de polymérisation en chaîne , TuberculoseRésumé
BACKGROUND: The 463 codon mutation of katG gene has been reported as an useful marker for the detection of isoniazid(INH) resistant strains of M. tuberculosis. This study aimed to elucidate relationship between 463 mutation in katG gene and INH resistance in M. tuberculosis. METHOD: DNA was extracted from 28 INH susceptible strains(MIC > or = 0.2microg/ml on the Lowenstein Jensen media) and used for amplification of 189bp fragment containing 463 codon by PCR. Amplified fragments were digested by restriction enzyme Msp I, analyzed by single strand conformation polymorphism(SSCP) in the MDE gel and sequenced to prove mutation. RESULT: Only 7(25%) out of 28 were digestible by restriction enzyme Msp I. The SSCP pattern of 21 strains were distinctly different from that of M. tuberculosis H37Rv. Msp I undigestible PCR fragment was substituted at 463 codon from Arg(CGG) to Leu(CTG). CONCLUSION: This finding clearly indicate no relationship between 463 codon mutation of the katG gene and INH resistance.