The killer yeast Wickerhamomyces anomalus associated to the sand fly Phlebotomus perniciosus: possible implication against the pathogen Leishmania spp.

While arthropod-associated bacteria are the focus of several research programs aimed at developing strategies to control vector-borne diseases, such as malaria, dengue, and trypanosomiasis, arthropod-associated yeasts and their killer toxins have not yet been deeply investigated. I focused my work on the sand fly Phlebotomus perniciosus, the main vector of human and canine leishmaniasis in the western Mediterranean area, with the aim of investigating if a yeast associated with this arthropod could exert inhibitory/killing activity against the pathogen Leishmania spp. We isolated and phylogenetically characterized strains of the yeast species Wickerhamomyces anomalus, from laboratory-reared adults and larvae of P. perniciosus. The yeast W. anomalus is renowned for its potential in biocontrol and has been isolated from different substrates and habitats including several mosquito species, in witch it showed the ability to produce a killer toxin active against other yeast species. In the present research, the isolated yeast strains of the species W. anomalus were tested against sensitive yeast strains, demonstrating its killer phenotype. Finally, in order to explore the possibility that this yeast could exert inhibitory/killing activity against pathogens, I tested the in vitro activity of W. anomalus strains against Leishmania infantum. This study offers the basis for the development of a method for vector-borne disease control that is environment-friendly and safe for human health. The use of yeast symbionts with antimicrobial proprieties could be included in the integrated approach for the control of leishmaniases, a worldwide re-emerging public health problem.