Nicotine: Its Stimulating and Inhibitory Effects on Oral Microorganisms
Tobacco users are much more susceptible to dental caries and periodontal diseases than non-tobacco users. Research suggests that this increased susceptibility may be due in part to nicotine, a primary active component of tobacco. Five bacterial species and one yeast species commonly found in the human oral cavity, Lactobacillus casei, Actinomyces viscosus, Actinomyces naeslundii, Rothia dentocariosa, Enterococcus faecalis, and Candida albicans respectively, were utilized to investigate if any correlation existed between exposure to various concentrations of nicotine ranging from 0 to 32 mg/ml and the growth of each microorganism. The minimum inhibitory concentration (MIC), minimum biofilm inhibitory concentration (MBIC), and planktonic growth were measured. The MIC was determined to be 16 mg/ml for all organisms except E. faecalis, which had an MIC of 32 mg/ml. Nicotine had a varying effect on planktonic growth across the different species. A distinct upward trend in biofilm formation was found in A. viscosus, L. casei, E. faecalis, and C. albicans through 8 mg/ml. Nicotine also enhanced R. dentocariosa biofilm formation in all concentrations through 8 mg/ml but was most enhanced at 1 mg/ml. Alternatively, A. naeslundii exhibited a complete downward trend through 32 mg/ml. The MBIC was found to be 16 mg/ml in all organisms studied. These findings further support research suggesting that the increased susceptibility to oral health diseases experienced by tobacco users may be caused in part by an upregulation in biofilm formation of these oral pathogens.