Anti-drug Pattern of Drug-resistant Mycobacterium tuberculosis and Analysis of Mutation in Drug-target Genes

The antimycobacterial susceptibility test was performed and minimal inhibitory concentration (MIC) to drugs was determined in 98 strains of Mycobacteium tuberculosis (MTB) isolated in Tokyo from 2000 to 2003, to find which were resistant to any of the four main anti-MTB drugs, isoniazid (INH), rifampicin (RFP), streptomycin (SM), and ethambutol (EMB). 27strains of them were resistant only to SM, and 16 strains were resistant only to INH. 51 strains of them were resistant to not only INH but also other drugs. 38 strains were resistant to both INH and RFP. 19 strains were resistant to all four drugs, including 7 strains resistant to new quinolon anti-biotics also. Nucleotide or amino-acid mutations in drug resistant MTB genome were determined by DNA sequencing method. Mutation of codon 516, 526, or 531 of rpoB gene was detected in 98% of MTBs resistant to RFP. Deletion or insertion of katG gene or nucleotide mutation at regulatory region of ahpC gene was detected in MTBs highly resistant to INH. Amino acid mutation of katG gene, especially at codon 315, was detected in MTBs resistant to INH intermediate. Nucleotide mutations at regulatory region of inhA gene were detected in MTBs resistant to INH at low level. Amino acid mutation at codon 43 or 88 of rpsL gene was detected in MTBs highly resistant to SM, and nucleotide mutation at 512, 513, or 516 of rrs gene was detected in MTBs resistant to SM at low level. Amino acid mutation at codon 306 of embB gene was detected in 87% of MTBs resistant to EMB.