The infection of rat tongue mucosa in vitro with five species of Candida.

Orthokeratinised mucosa from the dorsal surface of neonatal rat tongue was maintained in culture and then infected with Candida albicans, C. tropicalis C. krusei, C. parapsilosis or C. guilliermondii for up to 45 h. The five species showed varying abilities to invade the tissues, which appeared to reflect their different pathogenicities. C. albicans was the only species able to invade all the tissues present, including the stratum corneum. C. tropicalis and C. krusei were able to invade connective tissue and the deeper nucleated cells of the epithelium but failed to penetrate the keratin layer, while C. parapsilosis and C. guilliermondii showed only slight invasion of the connective tissue. The keratin layer of rat tongue mucosa thus appeared to act as a barrier to invasion of the epithelium by anything but virulent species of candidal fungi. The results suggest that oral mucosa in vitro retains its structural integrity and that the tissues do not act solely as a passive growth medium through which any fungal strain might proliferate. It seems that this in-vitro system is representative of the in-vivo situation and forms a useful experimental model in which to investigate the host-fungal relationship in mucosal candidiasis.