Examination of Human Skin Surfaces for the Detection of Mycobacterium Ulcerans

Abstract

Mycobacterium ulcerans, causes Buruli ulcer (BU), a necrotizing skin disease endemic in 33 countries globally. Its environmental reservoir and mode of transmission are unknown. Portaels hypothesized that prior skin contamination followed by penetration through existing skin abrasion or trauma may be a possible route through which M. ulcerans is transmitted to humans. Comparative epidemiological and case control studies have outlined some risk activities associated with BU that could result in contamination of human skin with M. ulcerans. In this study, skin surfaces of inhabitants involved in specific risk activities in eight selected communities either BU endemic or non-endemic were examined for the presence of M. ulcerans. Skin swabs were taken from exposed limbs of 50 individuals from each community for the detection and isolation of M. ulcerans. Two DNA extraction methods were compared in extracting M. ulcerans DNA from pooled skin suspensions. The presence of M. ulcerans DNA from the extracts was first detected using Taqman real time IS2404 PCR multiplex with internal positive control and then IS2606 multiplex with KR for all IS2404 positives. None of the DNA extracts using modified Boom DNA extraction method was positive for IS2404 target sequence while three of the extracts using power soil DNA isolation kit were IS2404 positive. Only one of the IS2404 pooled positives was positive for both IS2606 and KR. Five individual samples within these three pools accounted for the pools positivity for IS2404, IS2606 and KR results. The difference in Ct value between IS2606 and IS2404 for one out of the five samples that was positive for all the targets was 2.34, an indication of M. ulcerans DNA. This was detected on an individual who was returning from the farm without protective clothing in a non-endemic community. No M. ulcerans was isolated from the LJ culture after 15 weeks of cultivation. Detection of M. ulcerans DNA on the skin surface of a farmer shows that the skin can be contaminated with M. ulcerans and supports Portaels‟ hypothesis about skin surface contamination with M. ulcerans. The findings also support the case control studies establishing association between BU with absence of protective clothing during farming.