The association between the killer yeast Wickerhamomyces anomalus and the sand fly Phlebotomus perniciosus: a potential tool for the control of leishmaniasis

INTRODUCTION: Leishmaniases are parasitic vector-borne diseases endemic in 98 tropical, subtropical and temperate countries. In particular, Italy is traditionally endemic for cutaneous and visceral forms of leishmaniasis caused by the protozoan Leishmania infantum, whose reservoir are dogs. The containment of leishmaniases should be based on a combination of chemotherapy, animal reservoir control and integrated vector control strategies. I focused my work on the study of the mycobiota of the sand fly\ua0Phlebotomus perniciosus, the main vector of human and canine leishmaniasis in the Mediterranean area, with the aim of identifying microorganisms useful for the biological control of Leishmania. Starting from my previous study on the yeast community of P. perniciosus (Martin et al., 2016, Med. Vet. Entomol, 30(1):101-106; Martin et al., 2018, Environ. Microbiol, 20(3):1064-1077), I investigated the potential of the yeast Wickerhamomyces anomalus for the development of novel tools for the control of L. infantum. MATERIALS AND METHODS: I isolated, screened and molecularly identified yeast strains of the species W. anomalus from P. perniciosus specimens. The isolated strains were phylogenetically characterized and tested against selected yeast strains. Finally, in order to investigate on the potential inhibitory/killing activity of the yeast against the pathogen Leishmania, I tested the in vitro activity of toxin-producer W. anomalus strains against L. infantum. RESULTS AND CONCLUSIONS: My results show that the W. anomalus strain isolated from P. perniciosus inhibits the growth of sensitive yeast strains, thus displaying a typical trait of the killer yeast phenotype. Furthermore, preliminary results of in vitro tests of this and other killer yeast strains against L. infantum indicate an inhibitory activity on promastigote replication, also with evidence for Leishmania cell degeneration. Killer toxin-producing yeasts are thus worth of further investigations, towards the development of novel arms for the biological control of leishmaniases