adverse effects of electronic cigarettes on the disease-naive oral microbiome.

Introduction:
This text provides a comprehensive analysis of the effects of electronic cigarettes (e-cigarettes) on the oral microbiome. The study combines comparative metagenomics, a rigorous case-control human study, and in vitro experiments to understand the potential mechanisms that underlie the shift in the oral microbial ecosystem caused by e-cigarette use. The text highlights the detrimental impact of e-cigarettes on the subgingival ecosystem, altering the immunotolerance of the host, and posing a significant risk for future disease.

Key Points:

* The study used a case-control human study with 123 periodontally healthy individuals, categorized into five groups: smokers, nonsmokers, e-cigarette users, former smokers currently using e-cigarettes, and concomitant cigarette and e-cigarette users.
* Subgingival plaque samples and gingival crevicular fluid (GCF) were collected, and DNa was isolated and subjected to metagenomic sequencing and analysis.
* Nonmetric multi-dimensional scaling (NMDS) revealed the duration of e-cigarette use as the strongest source of variation in the e-cigarette–influenced microbiome.
* E-cigarette users demonstrated enrichment of 284 genes, including those related to alanine and arginine biosynthesis, polyamine metabolism, central carbohydrate metabolism, one-carbon metabolism, mono-, di-, and oligosaccharide metabolism, fermentation, and cell division and cell cycle, compared to smokers and controls.
* E-cigarette users showed higher abundances of Gram-negative facultatives, while smoking selectively enriched for Gram-negative anaerobes.
* The study identified a robust common core microbiome in e-cigarette users that differed significantly from those of smokers and nonsmokers, suggesting that e-cigarette aerosol affects the oral microbiome differently than cigarette smoke.
* a Random Forest Classifier was used to predict ENDS users with 90% sensitivity and 97% specificity based on 49 genes encoding for Gram-positive and Gram-negative cell wall, peptidoglycan biosynthesis, and enzymes within the protein and amino acid metabolism pathway.

Main Message:
The study highlights the significant adverse effects of e-cigarettes on the disease-naive oral microbiome, which challenges the harm reduction narrative promoted by advertising campaigns. The findings emphasize the importance of understanding the potential risks associated with e-cigarette use, particularly in light of their growing popularity among young people. Regulatory bodies should consider these risks when developing policies and guidelines related to e-cigarette use.

Ganesan SM, Dabdoub SM, Nagaraja hN, et al. adverse effects of electronic cigarettes on the disease-naive oral microbiome. Science advances. 2020;6(22):1. doi:10.1126/sciadv.aaz0108