Opportunistic Pathogens of the Genus Cryptococcus in Louis Pasteur Days and in 200th Anniversary of his Birth

This year we are celebrating the 200th anniversary of the birth of Louis Pasteur, one of the fathers of microbiology. Interestingly, the time when Pasteur disproved the doctrine of „spontaneous generation” and announced the “germ theory of disease” coincides with the discovery of Cryptococcus neoformans and its role in cryptococcosis. Today, only in the realm of guesswork can remain the correct answer to the question „whether the observed parallelism of these events was accidental?” or „whether Pasteur’s discoveries constituted a solid foundation of the research on the etiological factors of cryptococcosis?”. Until recently, it might seem that all major virulence factors of pathogenic fungi of the Cryptococcus species complex have been thoroughly described. Meanwhile, the simultaneous publication in 2018 of three in vitro protocols for the induction of Titan cells, also known as giant cells, opened up new possibilities for research on the relatively uncharacterized virulence factor that is crucial for Cryptococcus spp. Research on the titanization process makes us realize how little we know about the virulence factors of these fungi, and how much more can be improved in the context of the treatment and prevention of cryptococcosis. The following review is not only a historical outline of research on Cryptococcus spp. and cryptococcosis, but also synthetically describes the virulence factors of these basidiomycetous yeasts, with particular emphasis on the titanization process. The phenomenon of titanization as a process of a specific morphological transformation, like Titan cells, are completely new terms in Polish literature, which will be introduced to readers here. We live in a post-antibiotic era where the lack of effective and non-toxic drugs affects patients all over the world. Specifically, the availability of only fluconazole, amphotericin B and flucytosine in therapy of cryptococcosis constitutes a significant limitation. For this reason, research on the virulence factors of Cryptococcus spp. will allow to find new effective antimycotics, including inhibitors of the titanization process.