Detection of isoniazid and rifampicin resistance by sequencing of katG, inhA, and rpoB genes in Korea.
BACKGROUND
In Korea, tuberculosis is resistant to isoniazid (INH) and/or rifampicin (RIF) in more than 10% of cases. To prevent the spread of resistant Mycobacterium tuberculosis strains, it is crucial to develop more rapid resistance detection methods.


METHODS
To determine the feasibility of using direct sequencing for detecting INH- and RIF-resistant strains, the katG gene, the regulatory region of the inhA gene, and the 81-bp hot-spot region of the rpoB gene from 95 culture isolates and 46 respiratory specimens were sequenced. Total 141 culture isolates were classified by conventional drug susceptibility testing (DST) as INH(R)/RIF(R) (N=30), INH(R)/RIF(S) (N=23), INH(S)/RIF(R) (N=15), and INH(S)/RIF(S) (N=73).


RESULTS
Compared with phenotypic DST, the overall sensitivity and specificity of sequencing were 83.0% (44/53) and 96.6% (85/88), respectively, for INH resistance, and 93.3% (42/45) and 100% (96/96), respectively, for RIF resistance. The rates were similar between culture isolates and respiratory specimens. Interestingly, three specimens with inhA -15C>T mutation were susceptible to INH by conventional DST.


CONCLUSIONS
Detection of mutations in the katG codon 315, the inhA regulatory region, and the hot-spot region of rpoB would be useful for rapid detection of INH and RIF resistance in Korea.
Cho
Eun Hae
EH
Greencross Reference Laboratory, Yongin, Korea. ehcho@mail.gcrl.co.kr
Bae
Hye Kyung
HK
Kang
Seong Ki
SK
Lee
Eun Hee
EH
D000995:Antitubercular Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics*; D002374:Catalase / Q000235:genetics*; D012321:DNA-Directed RNA Polymerases; D024901:Drug Resistance, Multiple, Bacterial; D005838:Genotype; D006801:Humans; D007538:Isoniazid / Q000494:pharmacology*; D009154:Mutation; D009169:Mycobacterium tuberculosis / Q000235:genetics* / Q000302:isolation & purification; D010088:Oxidoreductases / Q000235:genetics*; D056910:Republic of Korea; D012293:Rifampin / Q000494:pharmacology*; D012680:Sensitivity and Specificity; D017422:Sequence Analysis, DNA / Q000379:methods*
D000995:Antitubercular Agents; D001426:Bacterial Proteins; C505805:rpoB protein, Mycobacterium tuberculosis; D010088:Oxidoreductases; D002374:Catalase; C480353:katG protein, Mycobacterium tuberculosis; C085257:InhA protein, Mycobacterium; D012321:DNA-Directed RNA Polymerases; D007538:Isoniazid; D012293:Rifampin