Identifying the yeast community in the sand fly Phlebotomus perniciosus: towards a strategy for yeast-mediated biological control of vector-borne diseases

Vector-borne diseases (VBDs) are one of the greatest public health problems worldwide and their control represents a key global public health challenge for the 21st century. In particular leishmaniases are considered a worldwide re-emerging health problem because they are spreading and this may be caused by climate and environmental changes. In this context, the increased awareness of the environmental and the public health problems caused by the excessive and uncontrolled use of insecticides to combat VBDs is leading to the development of alternative control strategies. While bacteria associated with arthropods are broadly studied and are the focus of several research programs aimed at developing strategies to control VBDs, such as malaria, dengue, and trypanosomiasis, arthropod-associated yeasts and their possible application in biocontrol have not yet been intensely investigated. The objective of this work was to study the yeast community associated with the sand fly Phlebotomus perniciosus, the main vector of leishmaniasis in the western Mediterranean area, with the aim of investigating their potential to interfere with Leishmania development in the insect. To reach this goal we associated culture-based methodology with culture independent methods: we performed yeast isolation and identification, 454 pyrosequencing, PCR screening and whole mount FISH with specific probes to identify the yeast species. We isolated the yeast Wickerhamomyces anomalus, a species known for its potential in biocontrol, from both male and female P. perniciosus, . This yeast was phylogenetically characterized and then tested against toxin-susceptible  yeast strains, demonstrating its’ killer phenotype. Finally, in order to explore the possibility that this yeast could exert inhibitory/killing activity against pathogens, we tested the in vitro activity of W. anomalus strains against the pathogen Leishmania infantum. This study offers the basis for the development of an environmentally-friendly and human health safe method for VBD control that could be included in an integrated leishmaniasis control program.