Inhibition of Streptococcus mutans Adsorption to Hydroxyapatite by Low-molecular-weight Chitosans

Abstract

The role of Streptococcus mutans in the initiation of dental caries has been recognized and attributed, at least in part, to its ability to colonize the tooth surface. Therefore, factors which prevent S. mutans attachment to hydroxyapatite (HA) are of considerable interest for the prophylaxis of this infectious disease. Chitosan, a chitin derivative by N-deacetylation, is an interesting candidate in this respect, since it stimulates the ordered regeneration of oral soft tissues, prevents the deleterious action of organic acid, and exhibits bactericidal action against several pathogens. In the present work, the efficacy of a low-molecular-weight chitosan (LMWC) and its derivatives N-carboxymethyl chitosan (NCMC) and imidazolyl chitosan (IMIC) in preventing S. mutans attachment to HA beads was assessed. The effects of chitosan on both sucrose-dependent and -independent adherence were evaluated. In both cases, when saliva-coated or uncoated HA beads were treated with any of the chitosans, a reduction in S. mutans adsorption ranging from 47 to 66% was observed. When HA beads were coated with saliva after the treatment with chitosan, neither carbohydrate caused a statistically significant reduction in S. mutans adsorption, suggesting that saliva deposition restores HA binding properties. Bacteria grown in the presence of chitosan subminimal inhibitory concentrations (sub-MICs) ranging from 12 to 500 micrograms mL-1 adsorbed poorly to HA and exhibited a lower affinity toward xylene than untreated controls. In the presence of chitosan sub-MICs up to 60 micrograms mL-1, an increase in the percentage of detached bacteria from two- to nine-fold was observed. The desorptive effect of chitosan was weaker when S. mutans had adhered to saliva-coated HA in the presence of sucrose. These results demonstrate that the presence of minor amounts of modified chitosans prevents S. mutans adsorption to HA and suggest that colonization of the tooth surface might be impaired by the use of toothpastes, mouthrinses, or chewing gums containing any of the tested polysaccharides.

Inhibition of adhesion of Streptococcus mutans to hydroxylapatite by commercial dairy powders and individual milk proteins

“…Size profile analysis of this HA was carried out using a Malvern Mastersizer (Malvern Instruments Ltd., Worcestershire, UK), and the average diameter (D [3,4]) of the HA beads was found to be approximately 10 lm. PBS-HA was prepared immediately before use in the adherence assays, and did not undergo any pre-treatment steps.…”

“…Preliminary experiments have indicated that the HA beads used in our laboratory are being coated with these dairy proteins, which is possibly contributing to a reduction in adherence of S. mutans. Adsorption of proteins to HA is quite complex since HA carries both positive and negative charges due to the presence of Ca 2+ and PO 4 3-, and the affinity of the former for negatively charged groups is higher than the affinity for phosphate groups for positively charged residues [29]. However, we cannot report that the inhibition of S. mutans to HA is solely due to this process, as there are other possible mechanisms that could be contributing to this inhibition, such as charge-chargerepulsion/attraction, hydrophobic interactions, steric hindrance and possible interference to the surface binding proteins associated with S. mutans.…”

“…Control of dental plaque currently relies on good oral hygiene such as brushing and flossing, the effects of which are increased when used in conjunction with antimicrobials [3]. Bacterial adhesion is regarded as the first step in pathogenesis, thus, a logical approach to prophylaxis of dental caries centers upon the inhibition of adhesion of S. mutans to the tooth surface [4]. Hydroxylapatite (HA) can be used as a suitable in vitro model of adherence to tooth surfaces.…”

Effect of Molecular Mass and Degree of Deacetylation of Chitosan on Adsorption of Streptococcus sobrinus 6715 to Saliva Treated Hydroxyapatite.

“…Tarsi et al 24) also demonstrated that low molecular weight chitosan had a selective action against S. mutans adhesive properties and reduced the adsorption to saliva-treated hydroxyapatite beads. They then assumed that the mechanism of anti-adherence activity seems to involve (1) bacterial surface modifications, (2) alterations in the expression levels of bacterial surface ligands, and (3) chitosan adsorption to host surfaces to change hydroxyapatite ionic properties.…”

“…Moreover, it was found that watersoluble chitosan possesses a cariostatic effect on caries increment in rats 21) . Recently Tarsi et al 24) also indicated that low molecular mass chitosan had an inhibitory effect on oral streptococci in a range of sub-minimal inhibitory concentrations.…”