Mycobacterium tuberculosis Strains H37ra and H37rv have equivalent minimum inhibitory concentrations to most antituberculosis drugs.

Background: Mycobacterium tuberculosis (Mtb) strains H37Ra and H37Rv are commonly used to study new and re-evaluate old antituberculous agents with respect to their pharmacodynamic effects in vitro. The differences in membrane proteins and, in particular, differences in carrier proteins between Mtb H37Ra and Mtb H37Rv may have an impact on antibiotic potency. The question of whether H37Ra can be used as a reliable surrogate for H37Rv and clinical strains has not been addressed sufficiently. The purpose of this study is to provide a full comparison of susceptibility data of the most common antituberculosis (TB) agents against both Mtb strains. Methods: In addition to a literature review, in vitro checkerboard susceptibility study was conducted comparing the in vitro minimum inhibitory concentration (MIC) of 16 common antituberculous drugs against H37Ra and H37Rv. Heifets-Sanchez TB agar drug susceptibility plates were utilized. Results: Half of the antibiotics demonstrated similar growth inhibition against both strains, while slightly differing MIC values were found for 7 of 16 drugs. With the exception of rifampicin, no marked difference in MIC against H37Ra and H37Rv was observed. Conclusion: While neither the attenuated (H37Ra) nor the virulent strain (H37Rv) is a clinical strain, both strains predicted MICs of clinical isolates equally well, when comparing the current in vitro results to clinical susceptibility data in the literature. H37Ra comes with the benefits of lower experimental costs and less administrative barriers including the requirement of a biosafety Level III environment.

Population pharmacokinetics and its role in anti-tuberculosis drug development and optimization of treatment.

Tuberculosis (TB) has survived for millennia due to its unique physiochemical properties and its ability to persist in a "dormant" state. Because of these unique properties, the treatment of TB involves multiple drugs for half of a year or longer. Although the incidence of TB has declined in most developing countries, it remains poorly controlled in much of the developing world. This is partly driven by co-infection with HIV in these settings. Concern about this dual epidemic has renewed interest in anti-tuberculosis drugs, and this in turn has led to increasing amounts of pharmacokinetic data regarding TB drugs. Population pharmacokinetics has proven useful for many disease states, providing a valuable tool with which to explore data and predict future events. It not only generates pharmacokinetic parameter estimates, but it includes patient characteristics (covariates) that may alter those parameters. We review the population pharmacokinetic studies undertaken with anti-TB medications. In addition to the primary medications used in TB treatment (rifampin, isoniazid, pyrazinamide, and ethambutol) we discuss the fluoroquinolones, various software packages, and the covariates that were found to be significant in each study.