Research ArticleMICROBIOLOGY

Adverse effects of electronic cigarettes on the disease-naive oral microbiome

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Science Advances  27 May 2020:
Vol. 6, no. 22, eaaz0108
DOI: 10.1126/sciadv.aaz0108
  • Fig. 1 Phylogenetic, functional, and immune characteristics of the subgingival microbiome of e-cigarette users.

    (A) Word map of the predominant microbial functions identified in e-cigarette users. The functions are colored by relative abundances (as indicated by the color map scale within each word map). (B) Network plot between eight immune mediators and the microbial metagenome, with the cytokines at the center of each hub. Interspecies networks are shown in (C). Each network graph contains nodes (circles sized by relative abundance per group) and edges (lines). Nodes represent cytokines and microbial genes in (B) and species-level OTUs in (C) and edges represent Spearman’s rho. In both network graphs, green edges indicate positive correlations and red edges indicate negative correlations. Only edges with correlation coefficient (Spearman’s rho) ≥ 0.80 and P < 0.05 are shown. The data supporting this figure can be found in table S1.

  • Fig. 2 Differences in microbial community structure and function between electronic cigarette users, smokers, and nonsmokers.

    LDA of relative abundances of functional genes in periodontally and systemically healthy nonsmokers (green), smokers (red), and ENDS users (blue) is shown in (A). The microbial profiles of subjects clustered by exposure type, creating three statistically significant clusters (P = 0.008, MANOVA/Wilks). Barycentric plots of significantly different virulence functions in the three groups (P < 0.05, FDR-adjusted Wald test) are shown in (B). Each dot represents a gene. The three groups (smoker, control, or e-cigarette user) are used as vertices. Within each plot, the coordinates of each gene are determined by the weighted average of the coordinates of all genes, and the weights are given by the relative abundance of the gene in that group (smoker, control, or e-cigarette user). Density curves of alpha diversity (ACE) are shown in (C). The peak indicates the median values for each group, and the x axis shows the data range. E-cigarette users demonstrated significantly greater alpha diversity than the other two groups (P < 0.0001, Kruskal-Wallis). LDA of relative abundances of sOTUs is shown in (D), while the relative abundances of selected species in each subject are shown in (E).

  • Fig. 3 Inflammatory burden imposed by the e-cigarette–influenced microbiome.

    Levels of selected immune mediators in periodontally and systemically healthy nonsmokers (green), smokers (red), and e-cigarette users (blue) is shown in (A). The y axis represents log10-transformed concentrations. Bars with the same symbol are significantly different (P < 0.05, Dunn’s test). Co-occurrence networks between cytokines and microbial genes in each group are shown in (B to D). Smokers are shown in (B), nonsmokers in (C), and e-cigarette users in (D). Each network graph contains nodes (circles) and edges (lines). Nodes represent cytokines and KEGG-annotated genes, and edges represent Spearman’s rho. Edges are colored green for positive correlation and red for negative correlation. Only significant correlations (P < 0.05, t test) with a coefficient of at least 0.80 are shown.

  • Fig. 4 The synergistic effects of smoking and e-cigarettes on the microbiome.

    LDA of Bray-Curtis dissimilarity indices based on relative abundances of species level OTUs (A) and functional genes (B) in periodontally and systemically healthy individuals who exclusively use ENDS (blue) or cigarettes (red), dual users (who use cigarettes and ENDS concomitantly, in tan color), former smokers who currently use ENDS (purple) and nonsmokers (green) are shown. Three statistically significant clusters were observed, with dual smokers and former smokers clustering along with exclusive ENDS users (P = 0.003, MANOVA/Wilks).

  • Fig. 5 Effect of e-cigarettes on sculpting the biofilm landscape.

    (A) SEM images of primary biofilms consisting of S. oralis, S. sanguis, S. mitis, A. naeslundii, N. mucosa, and V. parvula, secondary biofilms [following addition of an intermediate colonizer (F. nucleatum) to the primary biofilm] and tertiary biofilms (secondary biofilms seeded with P. gingivalis, F. alocis, Selenomas sputigena, S. noxia, C. gracilis, P. intermedia, P. micra, and T. forsythia) exposed to e-cigarette vapor with nicotine (6 or 0 mg/ml) and clean air controls. (B, i and ii) The effects of e-cigarette aerosol on area and volume of primary biofilms. (B, iii and iv) Changes in area and volume following addition of F. nucleatum. (B, v and vi) Changes in area and volume following addition of tertiary colonizers. Biofilms were visualized using confocal laser scanning microscopy in (B), and surface area and volume were computed with IMARIS. In all figures, groups connected by the same symbol are significantly different (P < 0.001, Dunn’s test with joint ranks).

Supplementary Materials

  • Supplementary Materials

    Adverse effects of electronic cigarettes on the disease-naive oral microbiome

    Sukirth M. Ganesan, Shareef M. Dabdoub, Haikady N. Nagaraja, Michelle L. Scott, Surya Pamulapati, Micah L. Berman, Peter G. Shields, Mary Ellen Wewers, Purnima S. Kumar

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