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CARACTÉRISATION MOLÉCULAIRE DES MYCOBACTÉRIES NON TUBERCULEUSES À L'INTERFACE HOMME-ANIMAL-ENVIRONNEMENT ET TRANSMISSION DE L'ULCÈRE DE BURULI DANS LES ZONES ENDÉMIQUES DE CÔTE D'IVOIRE

Abstract : The endemicity of Buruli ulcer (BU), a non-tuberculous mycobacteria (NTMs) infection, is the highest in Côte d'Ivoire (39.6 % of worldwide new cases in 2013). Epidemiological studies identified the mycobacteria producing mycolactone (MPMs), Mycobacterium ulcerans, as the causative agent and showed that aquatic environments represent the main source of infection. Many environmental reservoirs are suspected in transmission to humans; however, the exact transmission mode remains unknown. Thus, assuming that their transmission depends on the overlapping ecology of human and animal habitats, this study aimed to characterize NTMs, particularly M. ulcerans and other MPMs, within human-environment-animal interface, in order to elucidate possible transmission routes. The characterization was performed for suspected environments including potential reservoirs as well as for human isolates of infection cases, within five BU endemic localities. There were two in Western Centre (Zaïbo, Gorodi) and three in Eastern South (Léléblé, Sokrogbo, Ahondo) areas in Côte d’Ivoire. The biological material collected included 195 environmental matrices (biofilms, soils, plant detritus and water filtrates) from 15 water bodies usually used by communities; 35 fine needle aspirations and swabs from lesions of 30 human cases of infection; organs and lesions samples from 111 trapped rodents from which 8 were observed with BU-like lesions. After DNA extraction, a screening for Mycobacterium spp and MPM using the mycobacterial 16S rRNA and IS2404 genes was performed. Then, VNTR loci (MIRU1, locus 6, ST1 and locus 19) were used to genotype isolates of MPMs. The majority of environmental matrices (52.8 % for 16S rRNA, 8.7 % for IS2404) were contaminated by MPM with mostly water filtrates. All the VNTR loci were not amplified with theses samples but sequencing of positive ones identified M. ulcerans Agy99 and M. liflandii, among contaminated environments. Potential reservoirs were also identified regarding BU-like lesions, from two rodents (GP3a and ST1) belonging to Mastomys natalensis species, which showed 94 % and 98 % similarity with M. ulcerans Agy99 strain respectively. Besides that, 94.3 % of the 35 lesions of human infection were confirmed. VNTR typing of positive human samples identified five M. ulcerans genotypes, designated Q, R, S, T, and U; profile Q matching with the previously reported genotype C of M. ulcerans, common in Côte d’Ivoire and Ghana. These results highlight the presence of NTMs within investigated localities and suggest the role of environment in their dissemination including small mammal as infection sources. A new VNTR typing of isolates from contaminated environments, human and animal infection cases would allow precise source tracking of NTMs involved in human infection. Based on that, possible transmission pathways could be elucidated to ultimately promote adapted control policies in affected communities.
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Christelle Dassi. CARACTÉRISATION MOLÉCULAIRE DES MYCOBACTÉRIES NON TUBERCULEUSES À L'INTERFACE HOMME-ANIMAL-ENVIRONNEMENT ET TRANSMISSION DE L'ULCÈRE DE BURULI DANS LES ZONES ENDÉMIQUES DE CÔTE D'IVOIRE. Bactériologie. Université Félix Houphouët Boigny (Abidjan, Côte d'Ivoire); N°ORDRE 1005 / 2016, 2016. Français. ⟨tel-02417058⟩

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