The Genus Wallemia—From Contamination of Food to Health Threat

The fungal genus <i>Wallemia</i> of the order <i>Wallemiales</i> (Wallemiomycotina, Basidiomycota) comprises the most xerotolerant, xerophilic and also halophilic species worldwide. <i>Wallemia</i> spp. are found in various osmotically challenged environments, such as dry, salted, or highly sugared foods, dry feed, hypersaline waters of solar salterns, salt crystals, indoor and outdoor air, and agriculture aerosols. Recently, eight species were recognized for the genus <i>Wallemia</i>, among which four are commonly associated with foods: <i>W. sebi</i>, <i>W. mellicola</i>, <i>W. muriae</i> and <i>W. ichthyophaga</i>. To date, only strains of <i>W. sebi</i>, <i>W. mellicola</i> and <i>W. muriae</i> have been reported to be related to human health problems, as either allergological conditions (e.g., farmer’s lung disease) or rare subcutaneous/cutaneous infections. Therefore, this allergological and infective potential, together with the toxins that the majority of <i>Wallemia</i> spp. produce even under saline conditions, defines these fungi as filamentous food-borne pathogenic fungi.