Lower (1,3)-beta-d-glucan sensitivity and in vitro levels in Candida auris and Candida parapsilosis strains

Objectives: The serum (1,3)-beta-D-glucan (BDG) assay gives quicker results and has higher sensitivity than blood cultures, therefore it is advised for early diagnosis of invasive candidemia and/or discontinuation of empirical therapy. Its sensitivity may depend on different factors. The aim of our study was to analyse the in vitro and in vivo BDG levels in clinical isolates of three species of Candida responsible for candidemia. Methods: C. albicans, C. parapsilosis, and C. auris strains were collected from blood cultures of patients who had a concurrent (-1 to & thorn;3 days) serum BDG test (Fungitell assay). Supernatants of all strains were tested in quadruplicate for BDG levels. Results: Twenty-two C. auris, 14 C. albicans, and ten C. parapsilosis strains were included. The median BDG levels in supernatants were 463 pg/mL (interquartile range [IQR] 379-648) for C. auris, 1080 pg/mL (IQR 830-1276) for C. albicans, and 755 pg/mL (IQR 511-930) for C. parapsilosis, with the significant difference among the species (p < 0.0001). Median serum BDG levels (IQR) were significantly lower in case C. auris and C. parapsilosis vs. C. albicans (p < 0.0001), respectively, 50 pg/mL (IQR 15-161) and 57 pg/mL (IQR 18 - 332), vs. 372 pg/mL (IQR 102-520). Sensitivity of serum BDG was 39% (95% confidence interval [CI], 18 - 64) in case of C. auris, 30% (95% CI, 8-65) C. parapsilosis and 78% (95% CI, 49-94) C. albicans candidemia. Discussion: In our centre C. auris and C. parapsilosis strains have lower BDG content as compared with C. albicans, with a potential impact on serum BDG performance for the diagnosis of candidemia.