Stefan Rupf

Streptococcus sobrinus in children and its influence on caries activity.

Aim: This was to study the longitudinal assessment of caries activity of Streptococcus sobrinus (SS) positive children during their mixed dentition. Methods: The occurrence of mutans streptococci (MS) in plaque and saliva was determined in a representative sample of 55 children aged 8 to 12 years over a period of 4 years. A total of 708 bacterial strains was isolated which were identified as MS or SS. Caries activity (ΔD1−4MFS) as well as plaque and gingival inflammation were recorded. Results: During the period of observation 52 of the 55 children harboured MS; 12 of these children were SS positive. SS was not permanently detectable and 3 of the children were MS and SS negative. SS was not found without the presence of MS. Children that were infected with both SS and MS showed a slightly higher increase in caries compared with children that were infected exclusively by MS (ΔD1,2MFS 6.2 vs. 3.0 and ΔD3,4MFS 5.3 vs. 3.8) over the period of 4 years. An SS infection accelerated the increase of ΔD3,4MFS significantly by a factor of 4 one year after its detection, whereas the ΔD1,2MFS was 3 times as high during the period of infection. Conclusion: The findings suggest that an SS infection represents an important additional risk factor for dental caries due to its obvious aggravating of caries activity.

Peroxidase Reaction as a Parameter for Discrimination of Streptococcus mutans and Streptococcus sobrinus

425 strains of mutans streptococci and 12 reference strains were investigated by membrane fatty acid spectra (MFAS) and peroxidase reaction (PR) after aerobic and anaerobic incubation. 423 strains were identified as Streptococcus mutans. The remaining 2 strains were identified as Streptococcus sobrinus. The PR of 29 strains was doubtful; immediately after anaerobic incubation a negative PR changed into a slightly positive PR. To test the diagnostic value of PR the strains were additionally investigated by means of species–specific polymerase chain reactions (PCR). The species–specific PCRs were developed on the basis of the respective genes of 16S rRNA of the pathogens S. mutans and S. sobrinus. Specificity and sensitivity were tested on reference strains (n = 17) and negative control strains (n = 39). The results of this investigation showed that an anaerobic incubation regime could lead to false–positive (S. mutans) or false–negative (S. sobrinus) PR. The 425 MS strains were classified as either S. mutans (n = 420) or S. sobrinus (n = 5). The findings on the reference strains required a reclassification of S. mutans V 100 into S. sobrinus V 100. Summarising, it is possible now to differentiate strains of mutans streptococci by MFAS and PR after aerobic incubation.