Deletion of cyp125 confers increased sensitivity to azoles in mycobacterium tuberculosis

Mycobacterium tuberculosis is able to utilize cholesterol as a carbon source, and this ability is linked to its virulence in macrophages and in the mouse model of infection. The M. tuberculosis cytochrome P450 Cyp125 plays a key role in cholesterol metabolism being involved in the first steps of its degradation. Cyp125 is a cholesterol hydroxylase which is essential for cholesterol catabolism in M. bovis BCG and some strains of M. tuberculosis. We generated an unmarked, in-frame deletion of Cyp125 in M. tuberculosis H37Rv. The deletion strain was able to grow as well as wild-type in medium containing glucose as the carbon source. The Cyp125 deletion strain was more sensitive to growth inhibition by clotrimazole consistent with the ability of Cyp125 to bind azoles with high affinity. The deletion strain showed no difference in sensitivity to nitric oxide or hydrogen peroxide and was not attenuated for growth inside THP-1 human macrophage-like cells. These data suggest that the attenuation of virulence seen in operon deletion strains is not linked to the lack of Cyp125 alone.