Introduction: Candida auris is an emerging pathogen that causes nosocomial infections and is regarded as a significant global health concern. It was discovered as a new Candida species in 2009 and has since been isolated in 35 nations, except for Antarctica [1]. C. auris can cause invasive infections with a high mortality rate. It is a multi-drug resistant species with various resistance patterns to multiple antifungal drugs often used to treat other Candida infections. The growing incidence of infection and colonization with non-albicans Candida species in recent years is assumed to be owing to the overuse of prophylactic antifungals such as fluconazole. Laboratory yeast identification methods frequently misidentify C. auris as other yeasts, making discovering and treating this pathogen challenging. Candida auris transmission occurs in nosocomial settings, even when infection prevention and control measures are in place [2]. C. auris mannan differs from other pathogenic Candida species in its abundance of β-1,2-Man-linkages. The mannans are potent immunogens, and as such, the structure of the mannans and their epitopes have significant relevance to pathogenesis.

Aim: The presented work aims to analyze the changes in the structure of C. auris mannan from cultivation at 37 ºC in Shibata and YPD medium. The structure of mannan in C. albicans yeast and hyphal form (the most common morphological state at 37 °C, similar to the human body) is different; we investigate the comparative data, whether the similar structural change of mannan is fundamental for C. auris.

Method: Here, we extracted mannan from C. auris using two different media (Shibata and YPD medium) at 37 ºC. Mannan was isolated from cells using a modified extraction procedure [3]. Thus, the C. auris biomass was suspended in 0.2 M NaCl and autoclaved 3 × 1 h. Each time the supernatant was collected. Then the mannoprotein was precipitated using 3 vol. of EtOH. Pellet was suspended in H₂O and then dialyzed with 2 % KOH. Then the supernatant was saved and subjected to Fehling’s reagent for precipitation. The resulting precipitate was dialyzed again with 3 M HCl and methanol + acetic acid. After the sample was lyophilized, we obtained a product designed as mannan.

Results: As compared to the growth of cells between both media, it is found that the cells grew well in the YPD media. Further, the sample was characterized using NMR and FTIR techniques to analyze the structural changes of mannan within both media. The comparative data in FTIR shows little difference in the quality of mannans. However, mannan characterized from NMR shows under standard cultivation, Manβ1→2Manβ1→2Manα1→2 epitops are appr. 7 % of all mannoses present, but in the case of mannan with Shibata medium, they are 12 %. Manβ1→2Manα1→2 epitopes decreased from 4 % to 2 % for standard mannan. Whereas, in mannan, isolated from YPD, they are 6 %. Also, elemental analysis was done to analyze the amount of carbon, nitrogen, and hydrogen present in the mannan. The mannan extracted from the YPD shows a higher amount of nitrogen in comparison to the Shibata medium.

Conclusion: We concluded that cultivation with Shibata medium at 37 °C makes it challenging to yield an adequate quantity of mannan, whereas, in YPD, the yield was sufficient. The results in NMR indicate that the mannan structure appears similar under all examined conditions, and the differences may be due to the relative number of individual epitopes. We also need to perform GPC-HPLC to see molecular mass variations, among other things. In the future, we will extend our findings with further studies, providing the groundwork for getting previously undiscovered insights into the polysaccharides of C. auris virulence components.