Bactericidal effects of chitosan from squid pens on oral streptococci

Bactericidal effects of various chitosan samples from squid pens (SP-chitosan) against the Streptococcus mutans group have been investigated. Antimicrobial action of 0.0005% (5 mu g/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 similar to 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 ED(50) was 0.00007% (0.7 mu g/ml). In addition, its antibacterial activity against the same bacteria was greater with increasing degree oi 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.