Emerging Yeasts: Role of animals as reservoirs or spreaders of pathogenic strains

The present thesis provides original data on Emerging Yeasts: Role of Animals as reservoirs or spreaders of pathogenic strains. The thesis is divided into two chapters, in the format of a ‘thesis by publication’, encompassing published and submitted articles in international peer reviewed journals. Chapter I focuses on Emerging yeasts causing Human and animals infections and their possible circulation in Animals, Humans and Environment. In specifics, Chapter 1 is subdivided into three sections. Section 1 Highlights the role of Malassezia spp. in skin disorders. This review highlighted the most recent literature regarding Malassezia as a commensal or pathogenic organisms, highlighting Malassezia-associated skin disorders in humans and animals and their antifungal susceptibility profile. Section 2 specifically focused on pathogenesis and pathology of Malassezia species and their associated skin infections in Humans and Animals, Exogenous and endogenous risk factors and their possible role in inducing Malassezia phenotypic switch, Malassezia virulence factors, and the Immunomodulation of Malassezia skin disorders. Section 3 highlighted the Yeasts in the WHO Fungal priority list including Cryptococcus neoformans, Candida auris, Candida albicans, Candida tropicalis, Candida Parapsilopsis, Nakaseomyces glabrata, the Pichia kudriavzevii and Cryptococcus gattii, summarily expounded their presence in the environment, animals and humans as commensals and pathogens of diverse clinical conditions. Chapter II focuses on the role of wild animals in the spread of Human pathogenic yeasts in the environment it is divided into Four sections. Section 1 sought to investigate the virulence factors and in vitro antifungal susceptibility profiles of Malassezia furfur causing bloodstream infections (BSI) which were never investigated. This study suggests that M. furfur strains produce hydrolytic enzymes and biofilm when causing PV and BSI. Data suggest that the phospholipase activity, biofilm production, and a reduced antifungal susceptibility profile might favor M. furfur BSI, whereas lipase and hemolytic activities might display a synergic role in skin infection. Section 2 and 3 describes the role of Snakes as sentinel of zoonotic yeasts and bio-indicators of environmental quality. We investigated the occurrence of yeasts from the cloacal swabs of snakes of different origins and the antifungal profile of the isolated strains. The most frequently isolated species were Trichosporon asahii and Candida tropicalis from snakes from Morocco and Debaryomyces spp. and Metahyphopichia silvanorum from snakes in Italy. Worthy of mention in Section 3 was a novelty report of the isolation of Candida auris for the first time in a wild animal, an Egyptian cobra (Naja haje legionis).Multiple azole and amphotericin B (AmB) resistance phenomena were detected among isolated yeasts. Therefore, snakes may be considered as sentinels for human/animal pathogenic microorganisms and bio-indicators of environmental quality. Section 3 was dedicated to a novel report. The isolation of C. auris from wild animals is herein reported for the first time, thus suggesting the role that these animals could play as reservoirs of this emerging pathogen. Section 4 investigated the virulence factor of yeasts isolated from Reptiles which may act as reservoirs or spreaders of potential pathogenic microorganisms including Candida yeasts. Data show that yeasts from snakes were able to produce virulence factors, which vary according to the yeast species and the hosts or their origin, thus suggesting the potential role of snakes in harboring and spreading pathogenic yeasts in the environment. Since the virulence profile was lower in venomous snakes than that in non-venomous ones, we discussed that this finding will pave the way for fungal infection control, alternative to antifungal drugs in order to overcome resistance phenomena.