First Molecular Characterisation of Clinical Strains of Mycobacterium ulcerans in Togo (West Africa)

Background: Buruli ulcer is the third most common mycobacterial disease worldwide. Cases most occur in 30 countries but severe cases occur in West Africa countries such as Benin, Cote d’Ivoire and Togo mainly in rural regions. Early diagnosis may prevent severe disability. The molecular technique seems the best solution and new Mycobacterial Interspersed Repetitive Units (MIRU) and variable number tandem repeats (VNTR) typing method are themost reproducible in this regard. They propose geographical, inter and intraspecies differentiation and can be used as a diagnosis tool.

Objective: The objective of this study was to investigate the molecular diversity by using MIRUVNTR typing in clinical samples of BU patients in Togo.

Study Design: 64 DNA extracts from clinical samples were collected from BU patients in the two principal endemics districts in Togo (Yoto and Zio) with three less endemic districts (Bas Mono, Lacs and Vo). First, IS2404 and KR real-time PCR plus IS2606 conventional PCR were performed. In a second step, the strains were analysed by PCR typing for five specific and sensitive markers MIRU1, VNTR6, ST1, VNTR19 and VNTR9.

Results and Conclusion: 71.11% were positive for IS2404, 3.13% were positives for PCR-KR and 31.11% for IS 2606. By MIRU-VNTR typing, 48.86% positive result was found for MIRU1 and 25.00%, 20.31%, 18.75% and 14.06% for VNTR6, ST1, VNTR19 and VNTR9 respectively. One of the samples was negative for all genotyping markers. Two different genetic profiles were identified by MIRU1, ST1 and VNTR loci by gel-analysed of the amplified products. The VNTR profile B (3,1,1,2) corresponding of 3 copies MIRU1, 1 copy VNTR6, 1 copy ST-1 and two copies of VNTR19 was detected in 15.63% of samples and the VNTR profile A (1,1,1,2) corresponding of 1 copy MIRU1, 1 copy VNTR6, 1 copy ST-1 and 2 copies of VNTR19 was detected in 3.13% of samples and confirms the West African genotype (3,1,1) in Togo. Different genetic strains of Mycobacterium ulcerans (M. ulcerans) were co-circulated in the same endemic region in the country. This study has described first the circulating of different genetic strains of M. ulcerans in Togo.