[A primary investigation on the isoniazid-induced alterations in efflux gene expression among the isoniazid resistant Mycobacterium tuberculosis clinical isolates].

OBJECTIVE

To detect the changes on the expression of putative drug efflux genes caused by isoniazid-inducement in single resistance to the isoniazid Mycobacterium tuberculosis (M. tuberculosis) clinical isolates, for exploring the putative efflux genes which causing M. tuberculosis isoniazid resistance as well as the mechanism related to high expression of the putative efflux genes.

METHODS

We selected 35 M. tuberculosis clinical isolates which were only resistant to isoniazid as well as 10 sensitive M. tuberculosis clinical isolates and using H37Rv as control. Each strain was cultured in 7H9 liquid medium without isoniazid and with subinhibitory isoniazid concentration (1/4 MIC) induction. After RNA extraction and reverse transcription, real-time PCR was conducted to assess the expression changes of 27 putative drug efflux pump genes with formula 2(-ΔΔCT) to calculate the expression of each putative drug efflux pump genes.

RESULTS

Of the 27 putative genes, 13 of them were expressed at high level. High expression of Rv1258c gene had the maximum number of 6 strains, followed by high expression of Rv0849 and Rv2265 which both had 5 strains. Fourteen strains (40.00%) out of the 35 strains had high expression pump genes. Six strains (17.14%) had only one highly expressed putative efflux pump gene. Eight strains (22.86%) had two or more highly expressed putative efflux pump genes, including two, four, five, seven genes that highly expressed in 4, 2, 1, 1 strains respectively. For the 27 putative genes, ten sensitive strains and H37Rv did not show highly expressed genes.

CONCLUSION

Rv1258c, Rv2265, Rv0849, etc. genes might be the putative efflux pumps genes of M. tuberculosis resistant to isoniazid. Isoniazid might serve as the inducer of M. tuberculosis part putative efflux pump genes, inducing activation and causing high expression of these putative efflux pump genes.