Impact of biofilm formation on mortality in Candida tropicalis candidaemia: A retrospective study of ICU and Non-ICU patients

PURPOSE: To investigate the clinical factors associated with biofilm formation in Candida tropicalis bloodstream infections and to evaluate its impact on patient mortality in a high-prevalence setting in Thailand. MATERIALS AND METHODS: We retrospectively analysed 146 episodes (from 145 patients) of C. tropicalis candidaemia at a Thai referral centre (2015-2019). Biofilm formation was quantified by XTT assay and classified as low, moderate, or high. Clinical predictors of high biofilm formation (HBF) and associations with 30-day mortality were evaluated using regression and Kaplan-Meier analyses. RESULTS: Forty-nine isolates (33.6%) were HBF. Independent risk factors for HBF included shorter hospital stay prior to candidaemia (OR 0.98; 95% CI 0.96-0.999; P = 0.037) and recent Clostridioides difficile infection (OR 14.55; 95% CI 1.58-133.75; P = 0.018). Overall 30-day mortality was 74.0% and did not differ between HBF and non-HBF isolates (77.6% vs. 72.2%; P = 0.484). However, in non-ICU episodes, HBF was associated with significantly lower survival, whereas outcomes in ICU episodes were similar regardless of biofilm capacity. CONCLUSIONS: Biofilm formation in C. tropicalis candidaemia was linked to recent C. difficile infection and earlier onset of bloodstream infection, and predicted poorer survival in non-ICU episodes.