In Vivo Imaging of Bioluminescent Mycobacterium ulcerans: A Tool to Refine the Murine Buruli Ulcer Tail Model.

Buruli ulcer (BU) is a neglected tropical disease caused by infection with Mycobacterium ulcerans. Unclear transmission, no available vaccine, and suboptimal treatment regimens hamper the control of this disease. Carefully designed preclinical research is needed to address these shortcomings. In vivo imaging (IVIS®, Perkin Elmer, Waltham, MA) of infection is an emerging tool that permits monitoring of disease progression and reduces the need to using large numbers of mice at different time-points during the experiment, as individual mice can be imaged at multiple time-points. We aimed to further describe the use of in vivo imaging (IVIS) in BU. We studied the detection of M. ulcerans in experimentally infected BALB/c mouse tails and the subsequent histopathology and immune response in this pilot study. IVIS-monitoring was performed weekly in ten infected BALB/c mice to measure light emitted as a proxy for bacterial load. Nine of 10 (90%) BALB/c mice infected subcutaneously with 3.3 × 105 M. ulcerans JKD8049 (containing pMV306 hsp16+luxG13) exhibited light emission from the site of infection, indicating M. ulcerans growth in vivo, whereas only five of 10 (50%) animals developed clinical signs of the disease. Specific antibody titers were detected within 2 weeks of the infection. Interferon (IFN)-γ and interleukin (IL)-10 were elevated in animals with pathology. Histopathology revealed clusters of acid-fast bacilli in the subcutaneous tissue, with macrophage infiltration and granuloma formation resembling human BU. Our study successfully showed the utility of M. ulcerans IVIS monitoring and lays a foundation for further research.

[About a case of Mycobacterium ulcerans infection with cold abscess]. / A propos d'un cas d'infection due a Mycobacterium ulcerans se présentant sous la forme d'un abcès froid.

Buruli ulcer is still a public health problem in Côte d'Ivoire. Its physiopathology is poorly described and suggests a new clinical form. We report a clinical case in a 18-year-old patient who had a cold abscess on the right elbow. The histopathology test revealed a Mycobacterium ulcerans infection. The treatment consisted in antimycobacterial therapy and surgical care. The clinical healing was observed during 4 months of hospitalization. This form of Mycobacterium ulcerans with cold abscess, the first case described so far, requires great vigilance in clinical detection of cases and underlines the importance to intensify microbiological research mainly in endemic areas.

Ultrasonography for the monitoring of subcutaneous damage in Mycobacterium ulcerans infection (Buruli ulcer).

We used ultrasonography to evaluate the nature and the extent of subcutaneous damage provoked by Mycobacterium ulcerans (M. ulcerans) and to investigate the possible involvement of the tributary lymph nodes during the various stages of progression of Buruli ulcer. Nineteen patients affected by M. ulcerans infection in Benin, West Africa, were studied. Ultrasonography was performed on all subjects, except one, at the site of nonulcerated lesions and/or at perilesional site. The tributary lymph nodes were also studied in six patients. Ultrasound (US) evaluation was carried out using a 10 MHz linear probe and all lesions were compared with the homologous unaffected controlateral site. The ultrasonography showed relevant alterations at the dermo-hypodermic level, in agreement with histological specimens. In the active forms of the disease, these alterations are characterized by significant oedematous imbibition of the adipose tissue and necrosis (adiponecrosis) that leads to varying irregularities in the echogenicity of the hypodermis, which is generally thicker. In agreement with the clinical examination, the lymph nodes in six patients evaluated, despite their possible histological involvement with necrotic phenomena described in literature in M. ulcerans infection, did not display significant alterations visible by ultrasonography. The US scanning we have performed is the first use of this technique for M. ulcerans infection. We have shown that it can reveal the subcutaneous depth and the peripheral extent of the pathological process and it is particularly useful for monitoring the efficacy of or resistance to antibiotic treatment, especially in extensive ulcero-oedomatose forms. Such monitoring offers also a useful guide to the surgeon allowing the reduction or postponement of the removal of the large cutaneous areas that were carried out until recently.