Studies on strains of Streptococcus mutans isolated from caries-active and caries-free individuals in Iceland

BACKGROUND: Dental caries has been strongly associated with mutans streptococci, particularly Streptococcus mutans and S. sobrinus. Many studies have linked these organisms to the carious process and counts of mutans streptococci have been used to monitor caries risk. The high levels of caries generally found in Iceland have enabled several studies to be performed on the variation within strains of S. mutans. METHODS: This paper reports some studies showing phenotypic differences between strains of S. mutans that were related to whether the strain was isolated from an individual with active caries or from a caries-free subject. RESULTS: Strains from individuals with active caries generally adhered better to apatite, were more vigorous in decalcifying apatite and had bacteriocin-like activity that was likely to help the strain compete successfully with other strains, for example in the dental plaque biofilm. CONCLUSIONS: Phenotypic differences exist between strains of S. mutans depending on the caries activity of the individual from whom the strain was isolated.