Abstract
Many epidemilogical studies have shown that the mother might be a major source of infection for infants with S. mutans and that individuals did not harbour more than one serotype. However the results of the present epidemiological study indicated that many mother-child pairs harbored different serotypes and many individuals harbored plural serotypes. It has been shown that the necessary conditions for the colonization of S. mutans in man or animals are large and repeated inoculation. However, the obserbations in the present epidemiological study might indicate that various other factors, such as nourishmental conditions in the oral cavities, immunological specificity, synthesis of insoluble glucan etc., influenced the establishment of S. mutans.
Based on the previous reports that the predominant serotypes of S. mutans in infants changed with time and that they harbored plural serotypes as the result of infection with other serotypes, it is thought that bacteriocin anti-bacterial agents which many strains of S. mutans produce against other Gram-positive bacteria including S. mutans, play some role in infection and establishment.
The object of the present investigation was to clarify the role of bacteriocin in the infection and establishment of S. mutans by using strains of S. mutans isolated from a subject harboring two serotypes in the oral cavity. The results showed that even a small inoculum of the bacteriocinogenic strain of S. mutans could inhibit completely the establishment of its sensitive strains in cases of similtaneous infection with two strains.
Further, the bacteriocinogenic strain could eliminate sentitive strains when the latter made a slight colonization on the tooth surface preemtively. However, when sensitive strains were already established, the two coexisted and the bacteriocin production did not eliminate the sensitive strains. As these obserbations did not occur with the non bacteriocinogenic mutant, it was indicated that bacteriocin production of S. mutans played an important role in the infection and establishment of S. mutans.
