Comparative Structural Analysis of N-Linked Cell Wall Mannans Among Candida parapsilosis Sensu Stricto, Candida orthopsilosis, and Candida metapsilosis

The Candida parapsilosis complex (CPC), comprising Candida parapsilosis sensu stricto, Candida orthopsilosis, and Candida metapsilosis, is a significant cause of nosocomial candidemia worldwide. Because species-specific drug resistance profiles vary, accurate identification is clinically crucial; however, mainstream molecular diagnostics require expensive instrumentation. To establish a baseline for simple, cost-effective immunochemical diagnostics, we elucidated the cell wall N-linked mannan structures across representative CPC strains. Intact N-linked mannan cores were isolated via the classical Fehling method, which efficiently eliminated confounding O-linked glycans. Contrary to the historical paradigm suggesting a lack of branched side chains in C. parapsilosis, two-dimensional 1H-1H total correlation spectroscopy (2D-TOCSY) clearly identified a unique di-substituted branching residue, Manα1-2Manα1-3(Manα1-6)Man, corresponding to antigenic factor 4. Acetolysis and gel filtration demonstrated that the side chains ranged from a degree of polymerization (DP) of 2 to 6, with a tetrasaccharide serving as the structural mainstay. These results redefine the antigenic factor profile of C. parapsilosis as (1, 4, 13b), distinguishing it from C. orthopsilosis and C. metapsilosis (1, 13b). By integrating these N-linked profiles with our recent O-linked data, this study delineates the comprehensive cell wall surface architectures among the CPC. This framework provides a critical molecular foundation for the future development of rapid serological identification kits, while enhancing our understanding of evolutionary diversity and biosynthetic pathways within pathogenic yeasts.