title: Effect of rifampicin & isoniazid on cytochrome P-450 in mycobacteria.
abstract: OBJECTIVE
  Rifampicin and isoniazid are the most important first line drugs used in the treatment of tuberculosis. These drugs are also used in combination with other medications to treat co-infections. It, therefore, becomes important to study the effect of these drugs on the drug metabolizing system, namely, cytochrome P-450, not only in the host but also in the bacteria. We report the effect of rifampicin and isoniazid on the cytochrome P-450 activity in Mycobacterium smegmatis and M. tuberculosis H37Rv.
  
  
  METHODS
  Subinhibitory concentrations of rifampicin and isoniazid were added to the organisms after they had attained the growth phase and cytochrome P-450 activity was estimated in the membranous fractions of the bacteria at different time points.
  
  
  RESULTS
  Rifampicin was able to significantly enhance cytochrome P-450 in both M. smegmatis and M. tuberculosis H37Rv. Isoniazid was found to inhibit cytochrome P-450 in M. tuberculosis H37Rv, while there seemed to be no effect in M. smegmatis.
  
  
  CONCLUSIONS
  We report here the effect of rifampicin and isoniazid on mycobacterial cytochrome P-450. These findings are similar to those found in eukaryotic organisms. The role of mycobacterial cytochrome P-450 in the metabolism of drugs within the bacteria needs to be elucidated.
authors.affiliation: Tuberculosis Research Centre (ICMR), Chennai, India.
authors.forename: Geetha
authors.initials: G
authors.lastname: Ramachandran
authors.forename: Prema
authors.initials: P
authors.lastname: Gurumurthy
mesh_terms: D000995:Antitubercular Agents / Q000494:pharmacology*; D003577:Cytochrome P-450 Enzyme System / Q000187:drug effects* / Q000378:metabolism; D007538:Isoniazid / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D009161:Mycobacterium / Q000201:enzymology*; D012293:Rifampin / Q000494:pharmacology*
chemical_list: D000995:Antitubercular Agents; D003577:Cytochrome P-450 Enzyme System; D007538:Isoniazid; D012293:Rifampin