ECOLOGICAL STUDY OF STREPTOCOCCUS-MUTANS, STREPTOCOCCUS-SOBRINUS AND LACTOBACILLUS SPP. AT SUB-SITES FROM APPROXIMAL DENTAL PLAQUE FROM CHILDREN

Previous immunofluorescence (IF) studies have indicated that Streptoco ccus mutans may preferentially colonise specific sub-sites within appr oximal plaque. The present study aimed to extend these observations to other mutans streptococci and lactobacilli in such gingival margin pl aque. Two hundred and seventy approximal plaque samples were taken fro m 90 teeth (3 from each tooth) in 64 children; three gingival margin s ub-sites in relation to the contact area: away from (A), to the side o f (S) and below (B) the contact area. Samples were processed by indire ct IF using high-titred polyclonal anti-S. mutans 'c', anti-S. sobrinu s 'd', anti-L. casei and anti-L. acidophilus antisera. An overall posi tive association was found between S. mutans 'c' and S.sobrinus 'd' (p <0.001). Significant differences (p<0.1) were found between the propor tional counts at each sub-site for S. mutans 'c': A = 39%, S = 51% and B = 70%, and for S. sobrinus 'd' 21, 33 and 49%. Mutans streptococci (MS) appeared to preferentially colonise the sub-site below the contac t area (B = 81%), compared with sub-sites A and S (48 and 62%, respect ively). S. Mutans 'c' and S.sobrinus 'd' were detected together at sub sites A = 12%, S = 22%, and B = 38%, with proportional counts at B sit es being higher than those at A (B > A, p < 0.01, and B > S, p < 0.05) . Lactobacillus spp. were isolated rarely, and were usually found toge ther with MS. There was a positive relationship between the presence o f lactobacilli or MS and caries (white spot lesions only), although th ese species could frequently be isolated from non-carious sites. The p resence of both S. mutans 'c' and S. sobrinus 'd' were strongly correl ated with early caries lesions. In addition, this study confirmed the variation in the microflora at different sub-sites within approximal d ental plaque.