Drug Sensitivity Testing of Mycobacterium tuberculosis Growing in a Hollow Fiber Bioreactor

Hollow fiber systems (HFSs) have been widely applied to study pharmacokinetic-pharmacodynamic (PK-PD) relationships in antibiotic research and development. The system comprises a bundle of high-density hollow capillary fibers that conduct a flow of medium with or without drug and an extra-capillary space (ECS) inoculated with the pathogen of interest. The semipermeable membrane of the hollow fibers allows for rapid exchange of small molecule drugs and solutes, while the pathogen is restricted to the ECS. The unique properties of the HFS are (1) the ability to simulate any PK profile within the fibers and ECS, including plasma or site-of-disease PK profiles, (2) the ability to simultaneously input several drugs with different half-lives, (3) the ability to manipulate growth conditions such as medium composition, carbon source, and pH, and (4) the ability to sample in both compartments in order to monitor drug concentrations and bacterial growth kinetics over time. The system is particularly suited for Mycobacterium tuberculosis research in a biosafety level 3 (BSL3) environment since pathogenic bacteria are sequestered in an isolated compartment. The HFS was qualified by the European Medicines Agency for antituberculosis drug development in 2015. Here, we describe the standard procedures used to study the growth kinetics of M. tuberculosis in the HFS and the killing effect of first-line antituberculous drugs applied under simulated human PK conditions. This animal-sparing and economical tool can be applied to optimize dosing schedules that minimize emergence of resistance and to prioritize drug regimens that accelerate sterilization.