PMC

Photo: Jérome Constant, Department of Entomology, Royal Belgian Institute of Natural Sciences, Brussels, Belgium.

The two main characteristic fragments are those of the macrolide ring m/z = 429.4 (*) and the side chain at m/z = 359.3 (**).

The intact mycolactone can be identified at lower intensity at m/z 765.9 (**).

(In this case an ion trap was set to select for positive ions in the range m/z 755–775.)

BMDM were infected with M. ulcerans 00-1441 at an MOI of 1∶1. Macrophages were photographed by phase-contrast microscopy at 4 h (A), 4 days (B), and 6 days (C) postinfection. Macrophage cell rounding, shrinkage and detachment are present at days 4 and 6 post-infection.

BALB/c mice were infected subcutaneously in the footpad with 5.2 log¹⁰ AFB of M. ulcerans 00-1441. The degree of pathologic changes was assessed by measurement of footpad swelling (▪) (n = 8). The proliferation of bacilli in the footpad was determined by counting AFB (open bars) of footpad homogenates (n = 5). Significant differences were performed using Student's t test (**, p≤0.01).

NMRI mice were infected subcutaneously in the footpad with 5.4 log¹⁰ M. ulcerans 00-1441. At 6 weeks post-infection, bacilli were found both in the bone tissue and in the bone marrow (A, B and inset in D, arrows). Hemotoxylin-eosin staining of C and D reveals extensive destruction of bone. Outlines of dead cortical bone spicules are seen in C and D (arrowheads). Marrow is necrotic and replaced by chronic inflammation.

BALB/c (A–C) and NMRI (D) mice were infected subcutaneously with 5.4 log¹⁰ M. ulcerans 00-1441. At different time points the footpads were harvested and processed for histologic analysis. Dermal edema could be found by the second week of infection (A), along with a necrotic center surrounded by both chronic and acute inflammatory infiltrates (B) (hematoxylin-eosin stained sections). After 4 weeks of infection, bacilli were observed co-localized with cells (C) and in large clumps in the necrotic center of the lesion (D) (Ziehl-Neelsen stained sections).