Journal of Dental Research, Vol 76, 665-672, Copyright © 1997 by International & American Associations for Dental Research Online Journals
Inhibition of Streptococcus mutans adsorption to hydroxyapatite by low-molecular-weight chitosans
R. Tarsi, R. A. Muzzarelli, C. A. Guzman and C. Pruzzo
Institute of Microbiology, Faculty of Medicine, University of Ancona, Italy.
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.
