Abstract

Mycobacterium ulcerans is a slow-growing mycobacterium responsible for Buruli ulcer. The pathogenic virulence of MU is being linked to the expression of toxin called Mycolactone, whose form varies according to the origin of the productive strains. Forms A and B are secreted by African and Malaysian strains, C by Australian strains and D by Asian strains. Forms E and F of mycolactone are secreted by animal mycolactone producing mycobacteria strains. The genes for the biosynthesis of Mycolactone are located on a plasmid called pMUM001. We investigated the circulation of Mycolactone in body fluids coupled to the detection of virulence factors in MU strains. Suspicious BU patients and healthy subjects (negative controls) were selected in three Ivorian endemic areas. Exudates, fine needle aspiration (FNA) and blood samples were collected. Microscopy by Ziehl-Neelsen-staining, culture and PCR diagnostics using IS2404 and KR were performed in patient samples. The Mycolactone detection by HLPC coupled to MS was performed in patient and control samples. PCR using IS2404, IS2606, KR and ER were also performed in MU strains. Ziehl-Neelsen-microscopy detected acid-fast bacilli in 19% of samples while PCR were positive in 76.2% for IS2404 and 52.4% for KR. Mycolactone A/B was detected in 31% of exudates and in 42.8% of sera. No Mycolactone was detected in control subjects. 17 strains isolated from exudates possessed both IS2404 and IS2606. 70.6% of those strains were positive for KR and ER gene. The study shows that Mycolactone A/B was actually present in most of BU patients selected in three Ivorian endemic areas. With the methods used we detected very low concentrations in patient fluids. Plasmid and ER gene were found in the majority of MU strains. But they were not found in about 30% of strains. Mycolactone was detected only in patients infected by strains in which plasmid was found.

Key words: Buruli ulcer, Mycobacterium ulcerans, insertion sequence, virulence factor, Mycolactone.