Bactericidal Effects of Chitosan from Squid Pens on Oral Streptococci

Abstract

Bactericidal effects of various chitosan samples from squid pens (SP-chitosan) against the Streptococcus mutans group have been investigated. Antimicrobial action of 0.0005% (5μg/ml) SP-chitosan varied greatly depending on the molecular weight of chitosan as well as the species of oral streptococci. The SP-chitosan samples with molecular weights in the range 70-426 kDa had marked antibacterial activity on all the streptococci tested. S. mutans, S. sobrinus, and S. salivarius turned out to be especially sensitive to the SP-chitosan. The bactericidal effect of the 220 kDa SP-chitosan was observed even in a short incubation time (15 sec.) against S. mutans strain GS 5, and its ED₅₀ was 0.00007% (0.7μg/ml). In addition, its antibacterial activity against the same bacteria was greater with increasing degree of deacetylation of SP-chitosan. These results suggest that the SP-chitosan having a high molecular weight and high degree of deacetylation would be useful as an anti-caries agent.