Abstract
Tuberculosis remains a serious threat to human health world-wide, and improved efficiency of medical treatment requires a better understanding of the pathogenesis and the discovery of new drugs. In the present study, we performed a whole-cell based screen in order to complete the characterization of 168 compounds from the GlaxoSmithKline TB-set. We have established and utilized novel previously unexplored host-model systems to characterize the GSK compounds, i.e. the amoeboid organisms D. discoideum and A. castellanii, as well as a microglial phagocytic cell line, BV2. We infected these host cells with Mycobacterium marinum to monitor and characterize the anti-infective activity of the compounds with quantitative fluorescence measurements and high-content microscopy. In summary, 88.1% of the compounds were confirmed as antibiotics against M. marinum, 11.3% and 4.8% displayed strong anti-infective activity in, respectively, the mammalian and protozoan infection models. Additionally, in the two systems, 13–14% of the compounds displayed pro-infective activity. Our studies underline the relevance of using evolutionarily distant pathogen and host models in order to reveal conserved mechanisms of virulence and defence, respectively, which are potential “universal” targets for intervention. Subsequent mechanism of action studies based on generation of over-expresser M. bovis BCG strains, generation of spontaneous resistant mutants and whole genome sequencing revealed four new molecular targets, including FbpA, MurC, MmpL3 and GlpK.
Highlights
Tuberculosis remains a serious threat to human health world-wide, and improved efficiency of medical treatment requires a better understanding of the pathogenesis and the discovery of new drugs
One cannot ignore the changes of mycobacterial metabolism during infection[17], initiation of a dormant, persistent stage[18] and Mycobacterium tuberculosis (Mtb) switching from glycolysis to fatty acids metabolism[19,20,21]
The fact that the majority of the compounds decreased the rate of M. marinum growth indicates high potential for using this mycobacterial strain as a substitute for Mtb in classical antibiotic assays
Summary
Tuberculosis remains a serious threat to human health world-wide, and improved efficiency of medical treatment requires a better understanding of the pathogenesis and the discovery of new drugs. We have established and utilized novel previously unexplored host-model systems to characterize the GSK compounds, i.e. the amoeboid organisms D. discoideum and A. castellanii, as well as a microglial phagocytic cell line, BV2. We infected these host cells with Mycobacterium marinum to monitor and characterize the anti-infective activity of the compounds with quantitative fluorescence measurements and high-content microscopy. Tuberculosis (TB) remains one of the most serious health-threats worldwide with 8 million cases of new infection annually. Many drugs with a clinically relevant high bactericidal potency show comparatively insignificant effects in in vivo infection model systems[13]. One cannot ignore the changes of mycobacterial metabolism during infection[17], initiation of a dormant, persistent stage[18] and Mtb switching from glycolysis to fatty acids metabolism[19,20,21]
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