<i>M. ulcerans</i> in mouse footpads, before (A, 1–5) and after (B, 1–5) treatment with Rifampin-Streptomycin.

<p>A1: AFB are detectable in the dermis 3 days after infection with little or no cellular infiltrate. 500× Magnification A2: At day 7, the migration of inflammatory cells and phagocytosis has begun. 500× Magnification A3: By day 13, AFB are primarily associated with inflammatory and phagocytic cells. 1000× Magnification A4: At day 20, the extracellular phase of <i>M. ulcerans</i> infection has begun, coinciding with the onset of footpad swelling. 1000× Magnification A5: At day 27, shortly after the initiation of antibiotic treatment, a mix of intracellular and extracellular AFB is observed. 500× Magnification In panel B, untreated footpad lesions are shown on the left and treated footpads are shown on the right. B1: At day 34 after infection and after 10 days of treatment, <i>M. ulcerans</i> bacilli in treated mice are primarily associated with host cells whereas the bacilli are outside of cells in untreated mice; the cells are either not recruited or may have been destroyed by the mycolactone toxin. 500×, inset 1000×, Magnification, B2: At day 40, bacilli are found in extracellular masses in untreated mice but in mice treated for 16 days, the bacilli are still associated with host cells and stain less solidly. 500×, inset 1000×, Magnification B3: At day 48, after 24 days of treatment, the bacilli have lost solid staining and have become beaded in appearance. 500×, inset 1000×, Magnification B4: At day 55 after infection, <i>M. ulcerans</i> bacilli are apparent in the superficial dermis and epidermis and are being shed from the ulcerated lesions of untreated mice. 500×, inset 1000×, Magnification B5: 3 months after treatment completion, the organisms are uncultivable but non-solid staining bacilli are still present in the footpads. 500× Magnification.