Mycobacterium tuberculosis

The foundations of our understanding of intracellular parasitism by a range of eukaryote and prokaryote pathogens has been laid by using tissue culture infection models. These models, using defined cell lines or expanded primary cell cultures, have been invaluable in the generation of the knowledge base on which the field currently relies. However, the models artificially compress the heterogeneity that exists for all these pathogens in their natural in vivo infection cycle. It is the heterogeneity within the pathogen population that enhances a pathogen's capacity to adapt and survive under the different immune pressures and tissue environments within its host (1–3).