Mycobacteries non tuberculeuses dans les échantillons des patients tuberculeux admis pour retraitement en 2014 au Bénin: prévalence et facteurs associés

Introduction. Il n'existe pas de données sur la prévalence des Mycobactéries Non Tuberculeuses (MNT) au Bénin. L'objectif de ce travail était de déterminer la prévalence des MNT dans les échantillons des patients admis en retraitement au Bénin et d'identifier les facteurs associés. Patients et Méthode. Il s'agissait d'une étude transversale qui a porté sur les échantillons des patients admis en retraitement dans tous les Centres de Dépistage et de Traitement (CDT) de la tuberculose (TB) du Bénin en 2014. Un examen GeneXpert et une culture sur milieu de Lowenstein ont été réalisés sur les échantillons de crachat convoyés au Laboratoire de Références des Mycobactéries (LRM). La souche de mycobactéries a été identifiée grâce au MTB Complex Hain CM/AS assay sur les cultures positives. Résultats. Sur les 226 patients admis en retraitement en 2014 au Bénin, 214 échantillons ont été reçus au LRM. La culture était positive, négative et contaminée dans respectivement 58%, 40% et 2% des échantillons. Les MNT étaient retrouvées dans 10 échantillons soit une prévalence de 8,1% (10/123). Le complex MAC (M. avium et M. intracellulare) était le plus fréquent (4/10). Les MNT étaient majoritairement diagnostiqués dans les échantillons des patients admis pour rechute (7/10). Conclusion. Cette étude a permis de démontrer la présence des MNT dans les échantillons des patients admis pour retraitement au Bénin. Ce résultat devrait être pris en compte dans les stratégies de prise en charge des cas de retraitement

Genetic structure of farmer-managed varieties in clonally-propagated crops.

The relative role of sexual reproduction and mutation in shaping the diversity of clonally propagated crops is largely unknown. We analyzed the genetic diversity of yam-a vegetatively-propagated crop-to gain insight into how these two factors shape its diversity in relation with farmers' classifications. Using 15 microsatellite loci, we analyzed 485 samples of 10 different yam varieties. We identified 33 different genotypes organized in lineages supported by high bootstrap values. We computed the probability that these genotypes appeared by sexual reproduction or mutation within and between each lineage. This allowed us to interpret each lineage as a product of sexual reproduction that has evolved by mutation. Moreover, we clearly noted a similarity between the genetic structure and farmers' classifications. Each variety could thus be interpreted as being the product of sexual reproduction having evolved by mutation. This highly structured diversity of farmer-managed varieties has consequences for the preservation of yam diversity.

Farmers' use of wild relative and sexual reproduction in a vegetatively propagated crop. The case of yam in Benin.

The impact of traditional farmers' management on genetic diversity of vegetatively propagated crops is poorly documented. In this study, we analysed the impact of ennoblement of spontaneous yams, an original traditional farmers' practice, on the genetic diversity of yam (Dioscorea sp.) in Benin. We used 11 microsatellite markers on yam tubers from a small village in northern Benin and demonstrated that wild x cultivated hybrids are spontaneously formed. Many of the spontaneous yams collected by farmers from surrounding savannah areas for ennoblement were shown to be of wild and hybrid genotypes. Moreover, we demonstrated that some yam varieties have a wild or hybrid signature. Lastly, we performed a broader ranging genetic analysis on yam material from throughout Benin and showed that this practice is used in different ecological and ethno-linguistic regions. Through this practice, farmers create new varieties with new genetic combinations via sexual reproduction of wild and cultivated yams. This system, whereby a sexual cycle and asexual propagation are mixed, ensures potential large-scale cultivation of the best genotypes while preserving the potential for future adaptation.

Use of cpSSRs for the characterisation of yam phylogeny in Benin.

The Dioscorea cayenensis - Dioscorea rotundata species complex is the most widely cultivated yam in West Africa. This species complex has been described as deriving from wild yams belonging to the Enanthiophyllum section through domestication by African farmers. To study patterns of yam evolution and to establish phylogenetic relationships existing between wild and cultivated species sampled in Benin, we investigated changes in chloroplast DNA simple sequence repeats (cpSSR) in 148 yam accessions selected to cover the wider possible genetic diversity existing in the country. Dioscorea cayenensis and D. rotundata share the same haplotype. The morphotype "abyssinica" appeared to be subdivided into 2 haplotypes. One of these haplotypes shares the same haplotype with the Dioscorea cayenensis - Dioscorea rotundata species complex and with morphotypes praehensilis, suggesting that they might belong to the same species. Relationships among sections Lasiophyton, Macrocapaea, Opsophyton, and Enanthiophyllum were clarified, and some taxonomic changes within the Enanthiophyllum section were suggested. Dioscorea minutiflora, D. smilacifolia, and D. burkilliana might be considered as 1 single genetic group, and they are suspected of belonging to the same species.