264. Biofilm cells of Trichosporon asahii Show Higher Resistance Than Planktonic Cells to Various Abiotic Stresses

BACKGROUND: Biofilms of Trichosporon asahii are known to resist the effects of antifungal drugs, but the study of their susceptibility to various abiotic stresses remains sparse. This study was thus undertaken to compare the level of in vitro resistance of T. asahii biofilm and planktonic cells to various stress factors. METHODS: In this study, one T. asahii clinical isolate identified by amplifying IGS1 sequencing and one reference strain (NCCPF940033) were used. Biofilm and planktonic cells of T. asahii were exposed to increasing concentrations of NaCl (0.5–6 M) and d-sorbitol (3–13 M) for inducing osmotic stress; H(2)O(2) (5–50 mM), menadione sodium bisulfate (0.048–100 mM) and ox bile (1–12%) for oxidative stress; P(H) 1 to 13 for P(H) stress; congo red (600–10,000 µg/mL) for cell wall stress; CuSO(4)·5H(2)O/ZnSO(4)/FeSO(4) (1.25–2,560 mM) and MgSO(4) (250–3,000 mM) for metal stress. The biomass and metabolic activity of biofilms were quantitatively determined by crystal violet method and XTT reduction assay, respectively. Further, spot assay of serially diluted (10(–1) to 10(–6)) planktonic cells was performed on agar plates containing stress and non-stress control to determine relative percentage growth of strains. RESULTS: Biofilm cells of both the strains exhibited significantly higher (ANOVA) stress resistance than planktonic cells and on an average showed at least 100 times more resistant to stresses than planktonic cells [Minimum Biofilm Eradication Concentration (MBEC) vs. Minimum Inhibitory Concentration (MIC)]; H(2)0(2) >50 mM vs. 10 mM, Ox bile >12% vs. 2%, Menadione >100 mM vs. 0.39 mM, Zn/Fe/Cu >2,560 mM vs. 10 mM, Mg >3,000 mM vs. 1,000 mM, NaCl >6 M vs. 1.5 M, d-sorbitol >13 M vs. 5 M and Congo red >10,000 µg/mL vs. 800 µg/mL. Besides optimal P(H) 5–10, extreme acidic and alkaline P(H) led to complete inhibition of viable planktonic cells. Highest biomass reduction (77.2%) and highest viability inhibition (69%) of biofilm were observed at P(H) 3 and 13, respectively. Menadione reduced 86.9% biomass and 89.3% viability which accounted the highest biofilm inhibition. CONCLUSION: This is the first report on comparing the susceptibility of planktonic and biofilm T. asahii cells to various stress factors. The increased resistance of T. asahii biofilm may serve as a survival advantage against the host adversity. [Image: see text] [Image: see text] [Image: see text] [Image: see text] DISCLOSURES: All authors: No reported disclosures.