In:
Antimicrobial Agents and Chemotherapy, American Society for Microbiology, Vol. 58, No. 10 ( 2014-10), p. 6093-6100
Abstract:
Although the major causes of isoniazid (INH) resistance in Mycobacterium tuberculosis are confined to structural mutations in katG and promoter mutations in the mabA-inhA operon, a significant proportion of INH-resistant strains have unknown resistance mechanisms. Recently, we identified a high-level INH-resistant M. tuberculosis clinical isolate, GB005, with no known resistance-associated mutations. A comprehensive study was performed to investigate the molecular basis of drug resistance in this strain. Although no mutations were found throughout the katG and furA-katG intergenic region, the katG expression and the catalase activity were greatly diminished compared to those in H37Rv ( P 〈 0.01). Northern blotting revealed that the katG transcript from the isolate was smaller than that of H37Rv. Sequencing analysis of furA and upstream genes discovered a 7.2-kb truncation extended from the 96th base preceding the initiation codon of katG . Complementation of the M. tuberculosis Δ( furA-katG ) strain with katG and different portions of the truncated region identified a 134-bp upstream fragment of furA that was essential for full catalase activity and INH susceptibility in M. tuberculosis . The promoter activity of this fragment was also shown to be stronger than that of the furA-katG intergenic region ( P 〈 0.01). Collectively, these findings demonstrate that deletion of the 134-bp furA upstream fragment is responsible for the reduction in katG expression, resulting in INH resistance in GB005. To our knowledge, this is the first report showing that deletion of the upstream region preceding the furA-katG operon causes high-level INH resistance in a clinical isolate of M. tuberculosis .
Type of Medium:
Online Resource
ISSN:
0066-4804
,
1098-6596
DOI:
10.1128/AAC.03277-14
Language:
English
Publisher:
American Society for Microbiology
Publication Date:
2014
detail.hit.zdb_id:
1496156-8
SSG:
12
SSG:
15,3
