Fig 1.
Visualization of M. ulcerans within A. polyphaga trophozoites.
Panel A shows ZN stain of A. polyphaga trophozoites. No acid-fast particle was seen in the axenic culture of A. polyphaga trophozoites. Panel B shows a ZN stain of A. polyphaga trophozoites infected with M. ulcerans. A. polyphaga trophozoites stained bluish and M. ulcerans stained reddish- pink (acid-fast particles). Acid fast particles denoting the presence of M. ulcerans can be seen inside trophozoites of A. polyphaga infected with M. ulcerans. The average rate of infection was 47% ± 8.6 (SD) (average counts in 5 fields randomly selected under 200x magnification).
Fig 2.
Detection of strong RFP signals of M. ulcerans 1615::RFP inside trophozoites and cyst of A. polyphaga.
RFP signals were detected in trophozoites (3 days coculture) and also cyst (42 days coculture). Scale bar = 20μm.
Fig 3.
The progressive development of BU in mouse topically treated with M. ulcerans-infected A. polyphaga at the punctured skin of the rump (lower back).
Panel A shows site of inoculation 1 day post-inoculation (dpi). Panel B shows inflammation (erythema) at site of inoculation 31 dpi. Panel C shows an edema at site of inoculation 44 dpi. Panel D shows ulcer at the site of inoculation 49 dpi. Photograph is representative of group (n = 3).
Table 1.
The progression of BU signs in the various treatment groups post-inoculation.
Fig 4.
The progressive stages of development of BU in mouse injected in the right footpad with M. ulcerans-infected A. polyphaga.
Panel A shows footpad 1 dpi. Panel B shows footpad with erythema 3 dpi. Panel C shows footpad with edema 7 dpi. Panel D shows swollen footpad and thigh 25 dpi. The photographs are typically representatives of each group (n = 3).
Fig 5.
Demonstration of viable M. ulcerans in lesions.
Panel A shows a ZN stain of tissue homogenate from footpad of mouse injected with M. ulcerans-infected A. polyphaga. Profuse acid-fast particles (reddish pink) were seen in tissue homogenate. Panel B shows LJ slant (green) with colonies of M. ulcerans (yellowish) recovered from tissue homogenate of the footpad of mouse injected with M. ulcerans-infected A. polyphaga.
Fig 6.
Gross morphology and ZN-stained section of the ulcer showing the distribution of acid-fast bacilli (i.e. M. ulcerans).
Panel A shows undermined ulcer at the back of a mouse. Panel B shows ZN stained thin section of A´ with an arrow showing bed of acid-fast bacilli localized at the edge of the ulcer. Panel C shows ring-like clustering unit of acid fast bacilli in panel B (the scale bar measures 10 μm).