Nicotine and Arginine Increase Biofilm of Streptococcus mutans Serotype k Strains

Objectives:
Streptococcus mutans, a common oral bacteria causative of dental caries, is classified as serotypes c, e, f and k based upon cell wall/membrane polysaccharides. Serotype c is the most prevalent. Serotypes f and k strains comprise < 5% of S. mutans isolated from mouths of healthy subjects but are significantly increased in patients with cardiovascular disease (CVD). S. mutans serotype k strains are detected in diseased CV tissue at higher frequency than in the oral cavities of the same patients. Tobacco use is associated with increased risk for CVD and oral diseases, including caries. Nicotine, a bioactive agent in tobacco, increases in vitro biofilm formation by S. mutans serotypes c, e and f; effects on serotype k are unknown. Saliva contains arginine which alters adhesive/structural properties of the extracellular polysaccharides in S. mutans biofilm. We asked whether nicotine and arginine, affect S. mutans serotype k (n=10 strains) and serotype c (n=10) biofilm.
Methods: Biofilm was grown in tryptic soy broth with 1% sucrose (TSBS) without and with arginine and/or nicotine for 48h at 37^oC. Crystal violet staining quantified the biofilm.
Results: For all strains, maximum biofilm was produced in 4 and 8 mg/ml nicotine. Nicotine enhanced serotype k biofilm more than serotype c (P=0.01 & 0.02, respectively). UA159 (serotype c) biofilm was unchanged by 5 mg/ml arginine, whereas 5 of 7 serotype k strains yielded increased biofilm. Biofilm mass was greater when grown in nicotine than in arginine. Arginine did not enhance the effects of nicotine on UA159 but biofilm for 4 of 7 serotype k strains was increased by addition of arginine to nicotine.
Conclusions: Increased biofilm production by S. mutans serotype k strains in the presence of nicotine suggests that smokers’ increased risk for caries and CVD may be related to increased S. mutans biofilm growth caused by oral nicotine exposure.