P373 Does biofilm forming capacity of Candida tropicalis vary with echinocandin susceptibility?

POSTER SESSION 3, SEPTEMBER 23, 2022, 12:30 PM - 1:30 PM: OBJECTIVES: Candida tropicalis is a common cause of nosocomial candidemia and candiduria. The role of biofilm formation in virulence and antimicrobial resistance in C. tropicalis remains under-investigated. We aimed to evaluate the biofilm-forming capacity of C. tropicalis isolates exhibiting resistance, borderline resistance, and sensitivity to echinocandins. METHODS: The echinocandin resistant, borderline resistant, and susceptible isolates of C. tropicalis were collected based on their minimum inhibitory concentration (MIC) values according to Clinical and Laboratory Standard Institute (CLSI) broth microdilution guidelines. The isolates were subjected to FKS1 gene sequencing. To estimate biofilm production, echinocandin resistant (n = 2), borderline resistant (n = 5), and susceptible isolates (n = 3) were seeded at the cell concentration of 1 × 10⁶ cells/mL in RPMI-1640 with 0.165 M MOPS in polystyrene 96-well microtiter plates and incubated for 24 and 48 h at 37°C. The biofilm was quantified by crystal violet/safranin-based spectrophotometric method and XTT (2,3-Bis-(2-Methoxy-4-Nitro-5-Sulfophenyl)-2H-Tetrazolium-5-Carboxanilide) reduction assay. Statistical analysis was performed using one-way ANOVA with Bonferroni's post-hoc test for multiple comparisons among the groups. RESULTS: FKS1 sequencing analysis revealed S654P mutation in HS1 in both resistant isolates while isolates exhibiting borderline MIC to echinocandins carried wild-type FKS1 gene. Biofilm formation in borderline echinocandin-resistant C. tropicalis isolates was significantly (P <.005) higher compared with resistant and susceptible isolates. However, no significant difference in biofilm formation was noted among resistant and susceptible isolates. CONCLUSION: This study suggests differential biofilm-formation capacity among C. tropicalis isolates with reduced susceptibility to echinocandins. However, this warrants further studies before any definitive inference can be made.