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

BackgroundBuruli 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.MethodsA 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.ResultsIn 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.ConclusionThis 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.

Buruli Ulcer: a Review of the Current Knowledge

“…Currently, real-time PCR targeting M. ulcerans -specific DNA sequences (the insertion sequences IS 2404 and IS 2406 , and genes present on the mycolactone-encoding plasmid such as KR-B and ER) is the technique used most frequently in surveys of environmental specimens [ 12 , 16 ]. Although the presence of DNA does not provide definite proof of the presence of living bacteria, identification of M. ulcerans DNA has been successful in environmental samples ranging from water filtrates, soil, biofilms, fish, frogs, snails, crayfish, insects, to other invertebrates [ 14 , 17 – 31 ]. Reports of successful culture of live bacteria from environmental samples are much rarer but have been reported from samples of an aquatic insect (Hemiptera or water strider) as well as from moss and aulacode (greater cane rat) feces [ 14 , 15 , 32 ].…”

Environmental and behavioural factors associated with Mycobacterium ulcerans infection in the district of Lalo in Benin: A case-control study

“…Our analyses did not reveal a significant association between the proximity of water bodies to the subjects' homes and the risk of contracting BU. The pathogen Mu, which is responsible for BU, is found in the aquatic environment of endemic areas, as demonstrated by several studies (Wagner et al, 2008a;Marion et al, 2011;Maman et al, 2018a). Therefore, the disease could only occur through direct and frequent contact of the populations with this contaminated environment.…”

Mycobacterium ulceransin Mosquitoes and March flies captured from endemic areas of Northern Queensland, Australia

“…The detection of all three targets (IS 2404, IS 2606 and KR) with an expected ×Ct values (< 7) confirms the presence of M. ulcerans DNA in the sample. (17, 18).…”