Diversity in Antagonistic Interactions between Commensal Oral Streptococci and Streptococcus mutans

Abstract

Arginine metabolism via the arginine deiminase system (ADS) of oral bacteria generates ammonia, which can increase the pH of oral biofilms and decrease the risk for dental caries. Antagonistic interactions between ADS-positive and cariogenic bacteria in oral biofilms may be an important ecological determinant of caries. This study investigated the antagonistic potential and mechanisms of clinical isolates of arginolytic streptococci on and by Streptococcus mutans UA159, a well-characterized cariogenic human isolate. Low-passage isolates of Streptococcus gordonii, Streptococcus sanguinis, Streptococcus parasanguinis, Streptococcus australis, and Streptococcus cristatus inhibited the growth of S. mutans to various degrees when they were inoculated on growth media first or simultaneously with S. mutans. The antagonistic effects of arginolytic strains against S. mutans and the production of H₂O₂ by these strains were enhanced during growth in a less-rich medium or when galactose was substituted for glucose as the primary carbohydrate source. Pyruvate oxidase was the dominant pathway for H₂O₂ production by arginolytic strains, but lactate oxidase activity was also detected in some strains of S. gordonii and S. cristatus. UA159 inhibited the growth of all tested arginolytic strains when inoculated first, especially in aerobic conditions. However, the antagonistic effects of S. mutans on certain strains of S. gordonii and S. australis were not observed during anaerobic growth in the presence of arginine. Thus, arginolytic commensal streptococci may have a synergistically positive impact on the ecology of oral biofilms by moderating biofilm pH while antagonizing the growth and virulence of caries pathogens.

A Comparison of Flavorless Electronic Cigarette-Generated Aerosol and Conventional Cigarette Smoke on the Planktonic Growth of Common Oral Commensal Streptococci

“…It is important to note that tobacco smoke promotes biofilm growth of oral pathogens, including P. gingivalis, and S. mutans [22,58,[61][62][63][64]. The three commensal species in this study have been shown to arrest the growth of common pathogens [16,17,65]. Furthermore, S. mitis can help promote the development of Th17 T cells that can cross-react with Streptococcus pneumoniae, enhancing the immune response against this pathogen and consequently leading to its clearance [66].…”

“…In addition, the individual components of flavorless E-liquid (i.e., nicotine, PG, and VG), when analyzed separately, also showed no significant effects on the growth of the three species tested. A potential implication of these results is that flavorless E-liquids and their generated aerosol induce less tooth decay and periodontal disease than traditional cigarette smoke, especially since oral commensals are known to arrest the growth of common pathogens [16][17][18] known to induce dental caries [23,24], promote periodontitis [25][26][27], and increase the risk for atherosclerosis-related events [28][29][30]. If this is true, a case for improving oral health (and overall health) could be made by federal health regulatory agencies for promoting the use of electronic nicotine delivery systems over the use of traditional cigarettes as a means of harm reduction.…”

“…Smoking is known to disrupt this balance [6][7][8]. Common types of commensal streptococci include Streptococcus gordonii, Streptococcus mitis, and Streptococcus oralis [9][10][11][12][13][14], which live in symbiotic relationships with the host [15] and act as antagonists against pathogenic strains [16][17][18]. Additionally, smoking is known to decrease salivation, salivary quality, and salivary pH [19,20], leading to the promotion of Streptococcus mutans and Porphyromonas gingivalis [21,22].…”

Amino Sugars Modify Antagonistic Interactions between Commensal Oral Streptococci and Streptococcus mutans

“…Comparative and functional genomic analyses currently being performed on these and other recent isolates of S. sanguinis could shed more light on the cause of these distinct phenotypes. In a separate study that focused on the effects of arginine on the antagonistic interactions between oral commensals and S. mutans, it was shown that enormous diversity exists among commensal streptococci, both in their antagonistic capabilities and their susceptibility to S. mutans (48). Clearly, probing the basis for phenotypic variation among commensals and pathogens (49) remains an essential goal in efforts to improve caries risk assessment and intervention.…”

Fluorescence Tools Adapted for Real-Time Monitoring of the Behaviors of Streptococcus Species

“…An increase in the proportions of cariogenic bacteria under acidic conditions promotes the lower diversity of organisms within the biofilms and demineralization of the tooth enamel (12). Exploring the interactions between these health-associated commensals and acidogenic bacteria is critical for our understanding of the pathogenic potential of S. mutans and for the development of novel therapeutic interventions, e.g., probiotic strains that antagonize the growth of S. mutans through multiple pathways (32,39). The construction and use of the various streptococcal fluorescent strains described here should allow for better insight into the behaviors of multispecies biofilms.…”