Decreased cariogenicity of a mutant of Streptococcus mutans

Abstract

A strain of Streptococcus mutans was treated with a mutagenic agent. This resulted in isolation of a mutant which, compared to the original strain, had lost the ability to form sticky deposits on hard surfaces in sucrose medium. Apart from colonial morphology, the mutant had not changed in any other characteristic studied. In a 9-week experiment with SPF Syrian hamsters the average caries score induced by the mutant was significantly lower than that induced by the parent strain. In a 5-week experiment using germfree rats, the mutant had virtually lost its cariogenicity in sharp contrast to the original Strep, mutans. In all instances the implanted microorganisms could be recovered from the animals during all phases of the experiments.