Abstract
Persister cells are metabolically inactive dormant cells that lie within microbial biofilms. They are phenotypic variants highly tolerant to antimicrobials and, therefore, associated with recalcitrant infections. In the present study, we investigated if Trichosporon asahii and T. inkin are able to produce persister cells. Trichosporon spp. are ubiquitous fungi, commonly found as commensals of the human skin and gut microbiota, and have been increasingly reported as agents of fungemia in immunocompromised patients. Biofilms derived from clinical strains of T asahii (n=5) and T. inkin (n=7) were formed in flat-bottomed microtiter plates and incubated at 35°C for 48 h, treated with 100 μg/ml amphotericin B (AMB) and incubated at 35°C for additional 24 h. Biofilms were scraped from the wells and persister cells were assayed for susceptibility to AMB. Additionally, we investigated if these persister cells were able to generate new biofilms and studied their ultrastructure and AMB susceptibility. Persister cells were detected in both T asahii and T. inkin biofilms and showed tolerance to high doses of AMB (up to 256 times higher than the minimum inhibitory concentration). Persister cells were able to generate biofilms, however they presented reduced biomass and metabolic activity, and reduced tolerance to AMB, in comparison to biofilm growth control. The present study describes the occurrence of persister cells in Trichosporon spp. and suggests their role in the reduced AMB susceptibility of T. asahii and T. inkin biofilms.
Highlights
Trichosporon spp. are ubiquitous fungi, commonly found as commensals of the human skin and gastrointestinal tract (Duarte-Oliveira et al, 2017)
The present study aimed to evaluate if T. asahii and T. inkin are prone to develop dormant persister cells within biofilms and to suggest their importance in antifungal tolerance
Strains were recovered from storage and maintained on potato dextrose agar (PDA; Himedia, India), at 35°C, for 48 h
Summary
Trichosporon spp. are ubiquitous fungi, commonly found as commensals of the human skin and gastrointestinal tract (Duarte-Oliveira et al, 2017). The ability of Trichosporon species to cause systemic infections is likely associated with the expression of virulence factors, such as extracellular lytic compounds, and, most importantly, biofilms (Montoya et al, 2018), microbial communities surrounded by a polymeric extracellular matrix (Zhao et al, 2017). This structure expresses several mechanisms to escape the action of antimicrobials, as well as to resist physical stress, desiccation, UV radiation, and host immune system (Martinez and Casadevall, 2007; Polke et al, 2015). T. asahii biofilms may be up to 16,000 times more resistant to voriconazole, the most active antifungal against Trichosporon planktonic cells (Di Bonaventura et al, 2006)
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