Abstract
BackgroundMycobacterium ulcerans is a close derivative of Mycobacterium marinum and the agent of Buruli ulcer in some tropical countries. Epidemiological and environmental studies pointed towards stagnant water ecosystems as potential sources of M. ulcerans, yet the ultimate reservoirs remain elusive. We hypothesized that carbon substrate determination may help elucidating the spectrum of potential reservoirs.Methodology/Principal findingsIn a first step, high-throughput phenotype microarray Biolog was used to profile carbon substrates in one M. marinum and five M. ulcerans strains. A total of 131/190 (69%) carbon substrates were metabolized by at least one M. ulcerans strain, including 28/190 (15%) carbon substrates metabolized by all five M. ulcerans strains of which 21 substrates were also metabolized by M. marinum. In a second step, 131 carbon substrates were investigated, through a bibliographical search, for their known environmental sources including plants, fruits and vegetables, bacteria, algae, fungi, nematodes, mollusks, mammals, insects and the inanimate environment. This analysis yielded significant association of M. ulcerans with bacteria (p = 0.000), fungi (p = 0.001), algae (p = 0.003) and mollusks (p = 0.007). In a third step, the Medline database was cross-searched for bacteria, fungi, mollusks and algae as potential sources of carbon substrates metabolized by all tested M. ulcerans; it indicated that 57% of M. ulcerans substrates were associated with bacteria, 18% with alga, 11% with mollusks and 7% with fungi.ConclusionsThis first report of high-throughput carbon substrate utilization by M. ulcerans would help designing media to isolate and grow this pathogen. Furthermore, the presented data suggest that potential M. ulcerans environmental reservoirs might be related to micro-habitats where bacteria, fungi, algae and mollusks are abundant. This should be followed by targeted investigations in Buruli ulcer endemic regions.
Highlights
Mycobacterium ulcerans is the etiologic agent of Buruli ulcer, a disabling infection of the cutaneous and subcutaneous tissues [1,2,3]
The presented data suggest that potential M. ulcerans environmental reservoirs might be related to micro-habitats where bacteria, fungi, algae and mollusks are abundant
This should be followed by targeted investigations in Buruli ulcer endemic regions
Summary
Mycobacterium ulcerans is the etiologic agent of Buruli ulcer, a disabling infection of the cutaneous and subcutaneous tissues [1,2,3]. Over the past ten years, 83.6% (80.89–86.30) of cases were declared by eight West African countries [8] In these highly endemic regions, the exact reservoirs of M. ulcerans remain elusive [6, 9,10,11]. Epidemiological studies conducted in West African countries all indicated a significant association between the prevalence of Buruli ulcer and the contact of populations with stagnant water sources [12,13,14,15,16,17] through routine activities such as washing, swimming, fishing and farming [18,19]. M. ulcerans DNA has been detected in water plants [28,31] and in Thryonhuomys swinderianus (agouti), a small mammal causing damages to rice fields and in close contacts with rural populations in West Africa [20]. We hypothesized that carbon substrate determination may help elucidating the spectrum of potential reservoirs
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