Abstract
BackgroundDental plaque formed on tooth surfaces is a complex ecosystem composed of diverse oral bacteria and salivary components. Accumulation of dental plaque is a risk factor for dental caries and periodontal diseases. L-arginine has been reported to decrease the risk for dental caries by elevating plaque pH through the activity of arginine deiminase in oral bacteria. Here we evaluated the potential of L-arginine to remove established oral biofilms.MethodsBiofilms were formed using human saliva mixed with Brain Heart Infusion broth supplemented with 1 % sucrose in multi-well plates or on plastic discs. After washing the biofilms with saline, citrate (10 mM, pH3.5), or L-arginine (0.5 M, pH3.5), the retained biofilms were analyzed by crystal violet staining, scanning electron microscopy, and Illumina-based 16S rDNA sequencing.ResultsWashing with acidic L-arginine detached oral biofilms more efficiently than saline and significantly reduced biofilm mass retained in multi-well plates or on plastic discs. Illumina-based microbiota analysis showed that citrate (pH3.5) preferentially washed out Streptococcus from mature oral biofilm, whereas acidic L-arginine prepared with 10 mM citrate buffer (pH3.5) non-specifically removed microbial components of the oral biofilm.ConclusionsAcidic L-arginine prepared with citrate buffer (pH3.5) effectively destabilized and removed mature oral biofilms. The acidic L-arginine solution described here could be used as an additive that enhances the efficacy of mouth rinses used in oral hygiene.Electronic supplementary materialThe online version of this article (doi:10.1186/s12903-016-0194-z) contains supplementary material, which is available to authorized users.
Highlights
Dental plaque formed on tooth surfaces is a complex ecosystem composed of diverse oral bacteria and salivary components
This inhibition was unlikely to be due to a bactericidal effect, because 10 mM citrate buffer and L-arginine adjusted to pH3.5 reduced S. mutans GS5 number by only 0.61 ± 0.30 and 0.49 ± 0.22 log10 CFU/ml during a 5-min contact, respectively, and the optical density of the S. mutans culture after 24 h incubation was not different among the samples with and without 0.25 M L-arginine solution
These results suggest that acidic L-arginine destabilized biofilm structure and/or reduced insoluble glucan production of S. mutans
Summary
Dental plaque formed on tooth surfaces is a complex ecosystem composed of diverse oral bacteria and salivary components. L-arginine has been reported to decrease the risk for dental caries by elevating plaque pH through the activity of arginine deiminase in oral bacteria. Oral hygiene care is recognized as a critical measure that reduces the risks for health care-associated pneumonia (HCAP). Many clinical trials that investigated the effectiveness of oral hygiene care on prophylaxis for HCAP, including pneumonia arising from mechanical ventilation, have been reported. Oral cavities contain diverse microbiota that numbers nearly 700 species [14]. This ecosystem includes biofilm-forming bacteria such as Streptococcus mutans, Fusobacterium nucleatum, Porphyromonas gingivalis, and Aggregatibacter actinomycetemcomitans. Oral hygiene care for critically ill patients is especially important to prevent
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