Molecular analysis of katG gene mutations in strains of Mycobacterium tuberculosis from Korea

Park, Ae Ja; Lee, Mi Kyung

Abstract

BACKGROUND: The genetic basis of isoniazid (INH) resistance in Mycobacterium tuberculosis has been attributed to at least four genes. Mutations of the katG gene encoding catalase-eroxidase have been shown to cause resistance to INH. Among these mutations, the point mutation of codons 315 and 463 are frequently found. To determine whether simple screening method could potentially be useful for the detection of INH-esistant strains, we investigated the presence of mutation of codons 315 and 463 of katG gene in INH-esistant M. tuberculosis from Korea.
METHODS
We used the polymerase chain reaction (PCR) and direct sequencing analysis to detect the point mutation of codons 315 and 463 of katG gene in 48 strains of INH-esistant and 10 strains of INH-usceptible M. tuberculosis.
RESULTS
No amplification product was generated from 2 of 48 INH-esistant strains. Among the remaining 46 isolates, point mutations at codons 315 and 463 were identified in 19 isolates (41.3%) and 40 isolates (87.0%), respectively. Among the 10 INH-usceptible strains, the codon 463 point mutation was identified in 7 isolates, however, no point mutation of the codon 315 was found.
CONCLUSIONS
These results suggest that the point mutation of codon 463 of katG gene of M. tuberculosis may be a polymorphism not related with INH resistance. Although the mutation of codon 315 of katG gene was limited to 41.3% of INH-esistant isolates, further investigation of the codon 315 of katG gene should lead to increased understanding of resistance genes and the deveolpment of rapid molecular detection methods.