Norio Masuda

Dental caries induction in experimental animals by clinical strains of Streptococcus mutans isolated from Japanese children.

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 FAIR (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.

Demonstration of serotype d and g specificities of Streptococcus mutans by immunodiffusion

Abstract Although types d and g strains of Streptococcus mutans have been shown to be genetically homogeneous, a serological distinction between these two serotypes was demonstrated in immunodiffusion tests. Antiserum against Strep. mutans strain B13 (serotype d ) strongly cross-reacted with the autoclaved antigen obtained from type g strain OMZ65 and vice versa. Other strains of types d and g showed similar patterns in immunodiffusion tests. When the antiserum against type d or g strain was adsorbed with cross-reacting serotypes a , d or g cells, the adsorbed antiserum gave a specific precipitin band against the homologous antigen. Strep. mutans strain 6715 which had been designated type d was reclassified as type g because of the development of a single precipitin band between 6715 antigen and anti-OMZ65 (serotype g ) serum, adsorbed with types d and a cells. Furthermore, the four AHT substrains in our collection which had been classified as serotype a were found to be type g , on the basis of immunodiffusion pattern using type g and a specific antisera.

Lysis of Streptococcus mutans cells with mutanolysin, a lytic enzyme prepared from a culture liquor of Streptomyces globisporus 1829

Abstract A collection of reference and clinically-isolated strains of Streptococcus mutans and other streptococci were compared with regard to susceptibility to mutanolysin. This is a cell wall lytic enzyme prepared from a culture supernatant of Streptomyces globisporus 1829. Cells grown in Trypticase soy broth or brain-heart infusion broth were examined for lysis with mutanolysin, under various experimental conditions, with or without detergent. Most of the Strep. mutans strains studied were significantly lysed by the action of mutanolysin, especially when the incubation time was prolonged or if higher concentrations of the enzyme were used. Serotypes c , e and f strains were relatively resistant to the lytic action of mutanolysin as compared to strains of other serotypes. However, the viability of the cells of these strains was markedly decreased by mutanolysin treatment. The addition of a high concentration of sodium chloride after incubation with mutanolysin rapidly lysed the cells, even when the cells were seemingly resistant to the enzyme action. The simultaneous presence of sodium lauroyl sarcosinate and mutanolysin degraded the cells more rapidly and more extensively than the enzyme alone. Many other species of streptococci, including cariogenic strains, were also susceptible to the lytic action of mutanolysin.

Some biological properties of Streptococcus mutans isolated from human mouths, with reference to the correlation with serotypes.

Abstract Many strains (> 70 per cent) of serotype e Streptococcus mutans , in addition to those of serotype c (> 90 per cent) fermented melibiose, indicating that the fermentation of this sugar is not a criterion for distinguishing these serotypes. Strains of serotype c , e and f Strep. mutans gave rise to small, rough, raised and adherent colonies on mitis-salivarius agar, and were non-peroxidogenic and non-haemolytic on sheep blood agar. However, those of serotype d and g formed a marked zooglea around the colony, and were peroxidogenic and alpha haemolytic on sheep blood agar. These properties will be useful in distinguishing the two subgroups within the species of Strep. mutans .

Effect of Dextranase Prepared from Spicaria violacea on Dental Caries in the Hamster

Murayama et al (J Dent Res 52: 658, 1973) reported that intraoral administration of a dextranase (ex-l,6-glucanase) tablet prepared from culture liquor of Spicaria violacea IFO 6120 yielded modest reduction in the deposition of dental plaque in man. In this communication, golden hamsters were used to evaluate the anticaries effect of the dextranase. Dextranase AD17 from Sp violacea was prepared as previously described (MURAYAMA ET AL, J Dent Res 52: 658, 1973). No a-1,3-glucanase activity could be detected in dextranase AD17. The golden hamsters were purchased from a local dealer and were found to be free of Streptococcus mutans in their indigenous flora. The oral flora of the hamsters were depressed by administrating penicillin G in the drinking water (4,000 units/ml) and tetracycline in the powdered ordinary diet (4 mg/gm) from day 21 to 24 after birth. The hamsters were separated into three groups (1, 2, and 3) and were given diet no. 2000a from day 25 to the end of the experiment. Group I was the noninfected control and group 2 was the infected control. Group 3 was the experimental group that was given dextranase AD17 in both drinking water and diet no. 2000 in a final concentration of 10 units/gm. On day 25, 26, 27, and 28, the hamsters of groups 2 and 3 were infected orally with