Abstract
Mycobacterium tuberculosis (M.tb), the primary agent of human tuberculosis (TB), is a global problem of pandemic dimensions, despite the introduction of antibiotics against the disease happened more than 70 years ago. Today TB is the largest cause of death by a single infectious agent. Harsh and inadequate treatment often associated with lack of patient compliance, has in the past two decades led to the emergence of drug-resistant TB, which is hard to treat successfully. However, this negative development has in turn attracted significant attention in the field and consequently resulted in an increase in funding and research of new antibiotics against TB. One of the new drugs developed is pretomanid, a hydrophobic compound formerly known as PA 824. The drug is currently in phase III clinical trials and have displayed great promise. An important property of pretomanid is its ability to kill replicating, as well as non-replicating bacteria. The latter, being associated with persister bacilli, the main reason for why it is so difficult to eradicate TB completely. With the aim of improving the effectiveness of pretomanid against TB, in the last decade, approximately one thousand second-generation analogues have been synthesized and evaluated. The work described in this thesis investigates the therapeutic effect of a selection of these analogues, and more specifically the potential benefit of nanoparticle (NP) encapsulation. Although NP-based delivery of drugs is a relatively new field, there are several studies reporting on improved therapeutic outcome and lowering of toxicity when compared to free drug delivery. The NP-based approach is especially interesting with respect to hydrophobic compounds with poor oral bioavailability. Our work is performed using the embryonic zebrafish model for fish-TB (caused by Mycobacterium marinum, M.m) as an initial platform for rapid screening of the efficacy and general safety of the compounds. Based on these results, testing is then moved on to preclinical model, the mouse. In the zebrafish embryo, we observed a significant therapeutic effect when the compounds were in NP formulation. The free form of the hydrophobic drugs was extremely difficult to administer, and therefore only one of the compounds could be thoroughly examined as a free drug. Nevertheless, for this compound, the NP formulation was superior in fighting against the infection. Finally, this thesis describes the establishment of a new model for studying the fitness of M.m during TB infection by using the zebrafish embryo in combination with M.m expressing two fluorescent proteins.