Non-C. albicans Candida Species Develop Clinically Relevant Biofilms on Stainless Steel Under Respiratory Tract-Mimicking Conditions

Biofilm formation by non-C. albicans Candida (NAC) species is a major factor in device-associated infections, yet few studies have examined their development under physiologically relevant conditions. This study evaluated the biofilm-forming capacity of Candida tropicalis, Candida parapsilosis sensu stricto and Candida albicans on stainless steel surfaces in the presence of artificial saliva, simulating the respiratory tract environment of tracheostomized patients. Standardized inocula were incubated for 24 h, and biofilms were assessed through quantification of viable cells, biomass, biofilm matrix production and structural characterization by scanning electron microscopy (SEM). C. tropicalis produced the most robust biofilms compared to C. albicans and C. parapsilosis stricto sensu isolates, with significantly higher biomass and biofilm matrix (p < 0.001). C. parapsilosis sensu stricto developed less dense yet structurally defined biofilm networks. SEM confirmed mature and compact biofilm architecture, especially in C. tropicalis. These results demonstrate the strong intrinsic biofilm-forming ability of NAC species on stainless steel under host-like conditions, reinforcing their capacity to persist on medical surfaces and their relevance as independent contributors to biofilm-related contamination and infection.