Dental Caries Induction in Experimental Animals by Clinical Strains of Streptococcus mutans Isolated from Japanese Children

Abstract

Oral implantation and the cariogenic activity of clinical strains of Streptococcus mutans which had been isolated from Japanese children and labeled with streptomycin-resistance were examined in specific pathogen-free Sprague-Dawley rats. All the seven strains tested were easily implanted and persisted during the experimental period. Extensive carious lesions were produced in rats inoculated with clinical strains of S. mutans belonging to serotypes c, d, e, and f, and maintained on caries-inducing diet #2000. Noninfected rats did not develop dental caries when fed diet #2000. Type d S. mutans preferentially induced smooth surface caries in the rats. Strains of other serotypes primarily developed caries of pit and fissure origin. Caries also developed in rats inoculated with reference S. mutans strains BH-TR and FAlR (type b) that had been maintained in the laboratories for many years. However, the cariogenicity of the laboratory strains was found to have decreased markedly. All three S. sanguis strains could be implanted, but only one strain induced definite fissure caries. Two S. salivarius strains could not be implanted well in the rats and therefore they were not cariogenic. Four different species of lactobacilli also failed to induce dental caries in rats subjected to similar caries test regimen on diet #2000. S. mutans strain MT6R (type c) also induce caries in golden hamsters and ICR mice, but of variable degrees.

Detection of Caries‐Inducing Microorganisms in Hyposalivated Rats without Infection of Mutans Streptococci

“…In addition, the pH of the culture broth of heterofermentative lactobacilli is generally higher than that of homofermentative cultures, indicating less acidogenicity of the former. In our previous study, L. fermentum YIT 82R was shown to be noncariogenic in SPF rats fed diet 2000 for 89 days (12). Furthermore, L. fermentum TY 1 R used in this study did not induce significant dental caries in normally-salivated SPF rats fed diet 2000 (unpublished data).…”

“…carry any type of mutans streptococci in their indigenous oral microflora. The normally-salivated rats, therefore, could not induce significant dental caries when they are fed caries-inducing diet 2000 (12,24). In addition, no mutans streptococci could be detected from either the normally-salivated rats or the hyposalivated rats with rampant dental caries.…”

“…Because of their saccharolytic, acidogenic and aciduric capabilities, lactobacilli have been long believed to be associated with dental caries. However, lactobacilli constitute a minor proportion of the dental plaque microflora (29) and their cariogenicity in experimental animals is low (12). Hence, lactobacilli may not play a significant etiologic role in dental caries induction under the normally-salivated condition.…”

Cariostatic Effect of Palatinose on Experimental Dental Caries in Rats

“…S. mutans MT8148R (serotype c), which had been isolated from a carious lesion of a Japanese child and made streptomycin resistant, was used in the present study. The time schedule of the experiment, the experimental procedures, and the maintenance of the exprimental animals were described in the previous papers (Hamada et al, 1978;Ooshima et al, 1981Ooshima et al, , 1983. The basic experimental diet used in this study was cariogenic diet #2000 containing 56% sucrose (Keyes and Jordan, 1964).…”

Caries-inducing Activity of the Hydrogenated Derivative of an Isomaltooligosaccharide Mixture in Rats

“…2 ~ 4) Mutans streptococci are accepted to be one of the microorganisms responsible for dental caries, and their cariogenicity depends on the availability of sucrose. 5 ) Therefore, it has been suggested that one major method for preventing dental caries is to control sucrose consumption. Several investigators have examined the possibility of substituting sucrose by non-cariogenic sugars or sugar alcohols.…”