Salivary mycobial profiles of oral cancer patients–a cohort study

Background: Several studies have investigated the possible links between oral yeast infections and oral cancer. However, many of these studies concentrate on single species or genera and the overall oral mycobial profiles of oral cancer patients are not well known. 

Objective: We examined the salivary mycobial profiles of oral squamous cell carcinoma (OSCC) patients before and after cancer treatment and compared them with those of non-cancer controls. Additionally, we tested the recently introduced concept of two salivary mycotypes—one driven by the genus Candida and one by the genus Malassezia—in the context of OSCC. 

Design: Paraffin-stimulated saliva from OSCC patients before cancer treatment (n = 75), after a mean follow-up of 4 years (n = 27) and from non-cancer controls (n = 81) was analysed using ITS2 amplicon sequencing. 

Results: The OSCC patients had lower alpha-diversity (p = 0.001, Shannon diversity index) and higher relative abundance of OTU1 Candida albicans compared with controls. No significant difference in beta-diversity or in differential abundance of OTUs was found between the paired pre-treatment OSCC and follow-up samples or the follow-up samples and controls. Baseline OSCC patients had higher prevalence of the Candida-mycotype compared with controls (p = 0.019). The prevalence of the Malassezia-mycotype increased from baseline OSCC to follow-up. 

Conclusions: Our results suggest that OSCC patients have a Candida-dominated salivary mycobiota that differs significantly from that of non-cancer controls and shifts towards an increased prevalence of Malazzesia after cancer is treated.