Detection of Mycolactone A/B in Mycobacterium ulcerans–Infected Human Tissue.

Background: Mycobacterium ulcerans disease (Buruli ulcer) is a neglected tropical disease common amongst children in rural West Africa. Animal experiments have shown that tissue destruction is caused by a toxin called mycolactone. Methodology/Principal Findings: A molecule was identified among acetone-soluble lipid extracts from M. ulcerans (Mu)-infected human lesions with chemical and biological properties of mycolactone A/B. On thin layer chromatography this molecule had a retention factor value of 0.23, MS analyses showed it had an m/z of 765.6 [M+Na+] and on MS:MS fragmented to produce the core lactone ring with m/z of 429.4 and the polyketide side chain of mycolactone A/B with m/z of 359.2. Acetone-soluble lipids from lesions demonstrated significant cytotoxic, pro-apoptotic and anti-inflammatory activities on cultured fibroblast and macrophage cell lines. Mycolactone A/B was detected in all of 10 tissue samples from patients with ulcerative and pre-ulcerative Mu disease. Conclusions/Significance: Mycolactone can be detected in human tissue infected with Mu. This could have important implications for successful management of Mu infection by antibiotic treatment but further studies are needed to measure its concentration. Author Summary: Skin infection with bacteria called Mycobacterium ulcerans causes Buruli ulcer, a disease common in West Africa and mainly affecting children. M. ulcerans is the only mycobacterium to cause disease by production of a toxin. This lipid molecule called mycolactone diffuses from the site of infection, killing surrounding cells and, at low concentration, suppressing the immune response. The aim of this study was to show that mycolactone can be detected among lipids extracted from human M. ulcerans lesions in order to study its role in the pathogenesis of M. ulcerans disease. Lipids were extracted from skin biopsies and tested for the presence of mycolactone using thin layer chromatography and mass spectrometry. The extracts were shown to kill cultured cells in a cytotoxicity assay. Mycolactone was detected in both pre-ulcerative and ulcerative forms of the disease and also in lesions during antibiotic treatment but with reduced bioactivity, suggesting a lower concentration compared to untreated lesions. These findings indicate that there is mycolactone in affected skin at all stages of M. ulcerans disease and it could be used as a biomarker for monitoring the clinical response to antibiotic treatment. [ABSTRACT FROM AUTHOR]