FIG. 1.

Cytotoxic activity and virulence of different strains of M. ulcerans. (Left) BMDM were infected with different strains of M. ulcerans at an MOI (bacilli/macrophages) of 1:1. Macrophages were photographed by phase-contrast microscopy 6 days after infection. M. ulcerans cytotoxicity was determined based on the microscopic observation of cell rounding and detachment from the monolayer. (Right) Mice were infected in the left hind footpad with 5.3 log₁₀ AFB of different M. ulcerans strains. Virulence was determined by measuring footpad swelling. For ethical reasons mice were sacrificed after the emergence of ulceration. Results are from one representative experiment out of three independent experiments.