Molecular detection of Mycobacterium ulcerans in the environment and its relationship with Buruli ulcer occurrence in Zio and Yoto districts of maritime region in Togo

Abstract

Background

Buruli Ulcer (BU) is a neglected tropical skin infection caused by Mycobacterium ulcerans. Residence near aquatic areas has been identified as an important source of transmission of M. ulcerans with increased risk of contracting Buruli ulcer. However, the reservoir and the mode of transmission are not yet well known. The aim of this study was to identify the presence of M. ulcerans in the environment and its relationship with Buruli ulcer occurrence in Zio and Yoto districts of the maritime region in south Togo.

Methods

A total of 219 environmental samples including soil (n = 119), water (n = 65), biofilms/plants (n = 29) and animals’ feces (n = 6) were collected in 17 villages of Zio and Yoto districts of the maritime region in Togo. DNA of M. ulcerans including IS2404 and IS2606 insertions sequences and mycolactone ketoreductase-B gene (KR-B) was detected using real time PCR amplification (qPCR) technique. In parallel, clinical samples of patients were tested to establish a comparison of the genetic profile of M. ulcerans between the two types of samples. A calibration curve was generated for IS2404 from a synthetic gene of M. ulcerans Transposase pMUM001, the plasmid of virulence.

Results

In the absence of inhibition of the qPCR, 6/219 (2.7%) samples were tested positive for M. ulcerans DNA containing three sequences ( IS2404/IS2606/KR-B). Positive samples of M. ulcerans were consisting of biofilms/plants (3/29; 10.3%), water (1/65; 1.7%) and soil (2/119; 1.5%). Comparative analysis between DNA detected in environmental and clinical samples from BU patients showed the same genetic profile of M. ulcerans in the same environment. All these samples were collected in the environment of Haho and Zio rivers in the maritime region.

Conclusion

This study confirms the presence of M. ulcerans in the environment of the Zio and Yoto districts of the maritime region of Togo. This may explain partially, the high rates of Buruli ulcer patients in this region. Also, water, plants and soil along the rivers could be possible reservoirs of the bacterium. Therefore, Haho and Zio rivers could be potential sources of infection with M. ulcerans in humans in these districts.

Author summary

Buruli ulcer is a skin disease caused by Mycobacterium ulcerans. Although residence near aquatic areas has been identified as an important source of increased risk of contracting Buruli ulcer, the reservoir and the mode of transmission are not well known. To improve the understanding of the mode of transmission of M. ulcerans in human, we report here the first study of detection of M. ulcerans in the environment and its relationship with BU occurrence in Togo. This study confirms the presence of M. ulcerans DNA in the environment of Zio and Yoto districts of the maritime region. This study provides information on some possible reservoirs of the bacterium such as water, plants/biofilms and soil. Also, in this article we showed that the rivers of Haho and Zio could be potential sources of infection of M. ulcerans in human. Finally, data obtained from this study could explain partially the high rate of Buruli ulcer cases in these two districts of the maritime region in south Togo.