Microbiome evaluation revealed salivary dysbiosis in addicts of betel nut preparations

Betel nut addiction is recognized as the causative agent of oral microbiome dysbiosis and other systematic disorders. A number of betel nut preparations containing ingredients such as slaked lime, catechu extract and tobacco are being commonly used particularly in South Asia. The underlying variations in the oral microbiome due to usage of betel nut preparations are poorly understood. We evaluated salivary microbiome in response to chewing of betel nut preparation(s). In order to assess the microbiome dynamics, metagenomic analysis of 16S rRNA gene (V3-V4 hypervariable region) from salivary bacteria in chewers of betel nut preparation (n = 16) and non-chewers (n = 55) was carried out by Greengenes and SILVA ribosomal sequence databases. It was observed that Gutka chewers demonstrated lower alpha diversity and number of bacterial genera than the non-chewers. Taxonomic assignment on phylum level revealed Firmicutes (p-value = 0.042 at 95% confidence interval) to be significantly more abundant in Gutka chewers in comparison with non-chewers. Beta diversity analysis at genus level by weighted unifrac distance matrices unveiled both groups to be divergent from each other. On the genus level, Veillonella (p-value = 0.015), Streptococcus (p-value = 0.026), Leptotrichia (p-value = 0.022) and Serratia (p-value = 0.022) species appeared to be significantly more abundant in Gutka chewers in comparison to non-chewers. The present study suggests salivary dysbiosis in response to gutka chewing and concludes that gutka chewers possess higher abundance of acidogenic and aciduric bacteria. This study contributes additional information regarding oral microbiome variations with response to gutka consumption.