Bacteriocin types of Streptococcus mutans in human mouths

Plaque samples were collected at three different tooth sites from each of four individuals. Where possible, one of the sites was a carious lesion and the other two were clinically sound surfaces of teeth in opposite quadrants. From another group, 11 tooth sites and saliva were sampled from each subject. After plating suitable dilutions of each sample on mitis-salivarius agar, three widely separated colonies of Streptococcus mutans were picked and the isolates characterized by their ability to produce bacteriocin against 14 selected indicator strains and by their sensitivity to 11 bacteriocinogenic strains of Strep. mutans. This bacteriocin-typing method was found to be sensitive and reliable, indicating its utility in epidemiological studies. The findings suggest that one type of Strep. mutans predominates in the individual human mouth; indeed, with few exceptions, only a single type was found in each person. It also appeared that the population of Strep. mutans was stable in each subject tested. It is suggested that intrafamilial transfer of the organism may occur as common types were not found except within family groups.