Smokeless tobacco consumption induces dysbiosis of oral mycobiome: a pilot study.

Smokeless tobacco (SLT) alters the oral microbiome of smokeless tobacco users. Dysbiosis of oral bacteriome has been determined; however, the mycobiome of SLT users has not been characterized. The oral mycobiome was assayed by amplification and sequencing of the fungal internal transcribed spacer (ITS1) region from oral swab samples of non-SLT users, SLT users (with or without oral lesions), and SLT with alcohol users. We observed that the richness and diversity of oral mycobiome were significantly decreased in SLT with oral lesions users than in non-users. The β-diversity analysis showed significant dissimilarity of oral mycobiome between non-users and SLT with oral lesions users. Linear discriminant analysis effect size and random forest analysis of oral mycobiome affirm that the genus Pichia was typical for SLT with oral lesions users. Prevalence of the fungal genus Pichia correlates positively with Starmerella, Mortierella, Fusarium, Calonectria, and Madurella, but is negatively correlated with Pyrenochaeta, Botryosporium, and Alternaria. Further, the determination of oral mycobiome functionality showed a high abundance of pathotroph-saprotroph-symbiotroph and animal pathogen-endophyte-epiphyte-undefined saprotroph at trophic and guild levels, respectively, indicating possibly major changes in normal growth repression of types of fungi. The oral mycobiome in SLT users was identified and comprehensively analyzed for the first time. SLT intake is associated with oral mycobiome dysbiosis and such alterations of the oral mycobiome may contribute to oral carcinogenesis in SLT users. This study will provide a basis for further large-scale investigations on the potential role of the mycobiome in SLT-induced oral cancer. KEY POINTS: • SLT induces dysbiosis of the oral microbiome that can contribute to oral cancer. • Oral mycobiome diversity is noticeably reduced in SLT users having oral lesions. • Occurrence of Pichia can be used as a biomarker for SLT users having oral lesions.