A pilot investigation into the influence of electronic cigarettes on oral bacteria

Mechanistic Effects of E-Liquids on Biofilm Formation and Growth of Oral Commensal Streptococcal Communities: Effect of Flavoring Agents

Background: Vaping has become a global health concern. As research continues, more studies are beginning to question the relative safety of E-liquid flavoring additives. The oral cavity is the first site of exposure to E-liquid aerosol, making it critical for investigation. Because of the importance of commensal bacterial biofilms for oral health, we sought to explore the effects of E-liquids ± flavors on the formation and growth of single- and multi-species biofilms and to investigate the mechanism of inhibition. Methods: Quantitative and confocal biofilm analysis, death curves, and colony-forming units (CFU) were evaluated with flavorless and flavored (tobacco, menthol, cinnamon, strawberry, blueberry) E-liquids using four strains of oral commensal bacteria (Streptococcus gordonii, Streptococcus intermedius, Streptococcus mitis, and Streptococcus oralis). Results: All flavoring agents show a dose-dependent inhibition in the growth of single-species and multi-species biofilms. Furthermore, CFUs, death curves, and light microscopy show that flavoring agents have a bactericidal mode of inhibition on the growth of these oral streptococci. Conclusions: These results show that flavored, rather than unflavored, E-liquids are more detrimental to biofilm formation and growth of oral commensal bacteria. Consequently, E-liquid flavorings agents could pose risks to the oral microenvironment, and by extension, to systemic health.

Effect of Cigarette and E-Cigarette Smoke Condensates on Candida albicans Biofilm Formation and Gene Expression

Smoking triggers environmental changes in the oral cavity and increases the risk of mucosal infections caused by Candida albicans such as oral candidiasis. While cigarette smoke has a significant impact on C. albicans, how e-cigarettes affect this oral pathogen is less clear. Here, we investigated the effect of cigarette and e-cigarette smoke condensates (CSC and ECSC) on C. albicans growth, biofilm formation, and gene expression. Whereas pure nicotine (N) at the minimum inhibitory concentration (MIC, 4 mg/mL) prevented C. albicans growth, enhanced biofilm formation was observed at 0.1 mg/mL. In contrast, at this nicotine sub-MIC (0.1 mg/mL) concentration, CSC and ECSC had no significant effect on C. albicans biofilm formation. Additionally, N, CSC, and ECSC increased the expression of HWP1 and SAP2 genes. The ECSC group exhibited elevated expression levels of the EAP1 and ALS3 genes, compared to the nicotine-free ECSC (-) control. Moreover, our in vitro study illustrated that the antifungal drugs, fluconazole and amphotericin B, alleviated the effect of nicotine on C. albicans gene expression. Overall, the results of the study indicated nicotine from different sources may affect the pathogenic characteristics of C. albicans, including hyphal growth, biofilm formation, and particularly the expression of virulence-related genes.

Influence of Electronic Cigarettes on Selected Physicochemical Properties of Saliva

(1) Background: Electronic cigarettes are gaining more popularity not only among cigarettes smokers. Firstly, e-cigarettes were perceived as less harmful than traditional cigarettes, however, nowadays, they are arousing more controversy. The aim of this study was to assess the impact of e-cigarette usage on selected physicochemical properties of saliva. (2) Methods: The study population included 128 patients: 40 patients using e-cigarettes, 39 patients smoking traditional cigarettes, and 49 non-smoking patients (non-smokers). Laboratory tests involved verification of saliva values of pH and concentration of total protein, calcium, and phosphates. (3) Results: Among e-cigarette users, the value of pH was lower and the concentration of total protein, calcium, and phosphates was higher than in the group of non-smokers. Statistically significant differences were observed in relation to calcium. Among traditional cigarette smokers, the value of pH was lower, concentrations of total protein and phosphates were higher than in the group of non-smokers. Statistically significant differences were observed in relation to total protein. (4) Conclusions: Saliva of e-cigarette users presents changes in physicochemical composition in comparison to traditional cigarette smokers and non-smokers, however, statistically significant differences were observed only in calcium concentration. Further longitudinal studies on a larger study group should be conducted to assess the effect of observed changes in oral health.