Our understanding of normal immunity to opportunistic fungal infection is limited by a lack of species-specific commensal/host/pathogen models. There are many species of opportunistic fungal pathogens (such as spp. and spp.) which exist as commensal organisms or are common in our environment. Therefore, we sought to develop a model of commensal opportunistic infection within zebrafish by identification of a normal commensal fungus that could act as an opportunistic pathogen.

Using dissections of guts we isolated a monoculture of a commensal yeast. The strain was identified as via DNA sequencing and phenotypic analysis (e.g. halotolerance). was isolated from six individual animals and three strains (DJ1-3) have been deposited in the CBS collection.

is a common commensal of animals, including humans and is a rare opportunistic pathogen. Our DJ1 strain was thermotolerant and grows at mammalian body temperature. We found it was easily phagocytosed by mouse macrophages, in some cases to the extent of host cell destruction. Infection of zebrafish larval model of opportunistic infection demonstrated could act as an opportunistic pathogen of its commensal host.

Thus, we have characterised the first commensal fungus to be isolated from zebrafish and demonstrated that it may be a potential opportunistic pathogen, as in humans. The study of in zebrafish therefore represents an unparalleled opportunity to understand the evolution of fungal immunology and the switch between commensal and pathogen.

  • This is an open-access article distributed under the terms of the Creative Commons Attribution License.

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