Anticariogenic or Antiperiodontitic Agent

1. Field of the Invention

The present invention relates to an anticariogenic or antiperiodontitic products such as beverages and foods which have an anticariogenic or antiperiodontitic activity.

2. Description of the Related Art

Several kinds of bacteriocins and other substances acting in a similar way to anti-bacterial substances against Streptococcus mutans, which is a major pathogen of dental caries, have been proposed, and several kinds of antibiotics are known, such as tetracyclines and others, against genus Bacteroides causing periodontitis. However, their side-effects, for example, the influence of these substances on the intestinal microflora, are not yet fully understood and, thus, these substances are not used in practice, because it has not been proved that they are safe for daily usage.

Accordingly, the objects of the present invention are to eliminate the above-mentioned possible side-effects in the prior art and to provide an anticariogenic or antiperiodontitic agent or composition having strong inhibitory effects on the growth of Streptococcus mutans causing dental caries and Bacteroides causing periodontitis and having no influence on intestinal microflora when orally administered.

Other objects and advantages of the present invention will be apparent from the following description.

In accordance with the present invention, there is provided an anticariogenic or antiperiodontitic agent or composition containing, as an active component, the bacterial cells and/or water-soluble extracts of a microganism belonging to the genus Streptococcus or the genus Lactobacillus having antibacterial activity against Streptococcus mutans or the genus Bacteroides.

The present invention will be better understood from the description set forth below with reference to the drawings, in which:

FIG. 1 is a graphical drawing illustrating the inhibitory effects of the hot water-soluble extracts of a strain L. fermentum AD 0002 (i.e., FERM BP-715) on the growth of S. mutans in various concentrations;

FIG. 2 is a graphical drawing illustrating the inhibitory effects of the hot water-soluble extracts of a strain L. salivarius AD 0001 (i.e., FERM BP-713) on the growth of S. mutans in various concentrations;

FIG. 3 is a graphical drawing illustrating the inhibitory effects of the hot water-soluble extracts of a strain S. faecium AD 1050 (i.e., FERM BP-714) on the growth of S. mutans in various concentrations;

FIG. 4 is a graphical drawing illustrating the inhibitory effects of the hot water-soluble extracts of a strain S. equinus AD 8005 (i.e., FERM BP-716) on the growth of S. mutans in various concentrations; and

FIG. 5 is a graphical drawing illustrating the inhibitory effects of the hot water-soluble extracts of a strain S. faecium AD 1051 (i.e., FERM BP-712) on the growth of S. mutans in various concentrations.

The present inventors have found that the cells of intestinal (lactic acid) bacteria isolated from healthy humans, and their soluble extracts, have strong inhibitory effects on the growth of S. mutans causing dental caries and Bacteroides causing periodontitis, and that these lactic acid bacteria and water-soluble extracts have shown no toxicity in animal experiments and have no influence on intestinal microflora when orally administered.

The types and bacteriological characteristics, the preparation of the anticariogenic or antiperiodontitic products, the anti-bacterial activity, the forms in practical use, and the like, of the bacteria and water-soluble extracts according to the present invention will now be described in detail hereinbelow.

Microorganisms suitable for use in the preparation of the bacterial cell product according to the present invention are those belonging to the genus Streptococcus and Lactobacillus, especially, S. faecius, S. equinus, L. fermentum, L. salivarius, and the like.

Typical examples of such microorganisms were deposited on Mar. 8, 1984 in the Fermentation Research Institute (FRI) in Japan (all numbers quoted as "FERM-P" in Table 1 refer to the deposition numbers of said Institute) and transferred to the Fermentation Research Institute (FRI) (i.e., International Depository Authority under Budapest Treaty in Japan) as the FERM-BP deposition numbers shown in Table 1 under the Budapest Treaty on the International Recognition of the Deposit of Microorganisms for the Purpose of Patent Procedure:

The screening methods and the typical microbiological properties of the above-exemplified strains according to the present invention can be summarized as follows:

1. Screening methods

The screening of the microorganisms can be carried out by a method disclosed by Watanabe, T. et al., in "Studies on Streptococci. I. Distribution of Fecal Streptococci in Man, Microbiol, Immunol. 25, 257-269 (1981)".

That is, as described in this literature, 10-fold diluted feces obtained from healthy humans were smeared on KMN agar (for streptococci) or LBS agar (for lactobacilli) and were aerobically (for streptococci) or anaerobically (for lactobacilli) cultivated at 37.degree. C. for 48 to 72 hours. The formed colonies were counted and were randomly isolated. The colony type and catalase-negative and Gram-positive spherical and rod-shaped bacteria were determined. The isolates were identified and classified by examining physiological, biochemical, and serological properties.

2. Identification of lactic acid bacteria isolated from human feces

The morphology of the colonies formed on the KMN agar (Table 2) and LBS agar (Table 3), the selected media for the isolation of the genus Streptococcus and Lactobacillus, respectively, was examined. Then, the isolated bacteria were identified by the Gram stain, the cell shape, and the physiological, biochemical, and serological properties. The following articles were used during this identification procedure:

(1) Clin. Bacteriol. 2, 197-239 (1975)

(2) Japan. J. Bacteriol. 24, 261-280 (1969)

(3) Microbiol. Immunol, 25, 257-269 (1981)

(4) J. Bacteriol. 86, 1275-1282 (1963)

(5) Bergey's Manual of Determinative Bacteriology, 8th ed., 490-509 (1974)

The typical bacteriological properties used as criteria for the identification of the exemplified strains according to the present invention are summarized in Tables 4 and 5.

3. Cultivation methods

The cultivation methods of these microorganisms are conventional as mentioned above. For example, the bacterial cells can be collected by stationary cultivations in Rogose broth medium consisting of the following composition under an aerobical condition, and can be harvested by centrifugation of the culture.

The dead cells having undergone various treatments, and the water-soluble extracts of the microorganisms used in the present invention and suitable for use as anticariogenic and antiperiodontitic agents, are typically prepared as follows:

1. Hot-water extraction

The harvested bacterial cells were suspended in water, and were heated at 80.degree. C. to 130.degree. C., preferably at 100.degree. C. to 125.degree. C., for several minutes to several hours with and without pressure. The water-soluble anticariogenically and antiperiodontitically active extracts were obtained by centrifugation, etc. to remove water-insoluble solids.

Physiological saline (0.85% NaCl, etc.), various kinds of pH-adjusted buffers, various kinds of salt solutions, water/alcohol (methanol, ethanol, etc.) >1/3 (w/w), and various aqueous solvents can be also used for the extraction. Moreover, the whole cell preparations heat-treated in hot-water as described above can be also used for suitable anticariogenic and antiperiodontitic agents of the present invention, as powder or other preparation forms, by lyophilization, drying in vacuo, and spray drying.

2. Sterilization

The cell preparations made by spray-drying or heat-treatment with other methods or sonication (for example, at 15 KC for 1 hour) can be also used for anticariogenic and antiperiodontitic agents of the present invention. And the water-soluble components of the sterilized cell preparations as shown above can be also used for anticariogenically and antiperiodontitically active fractions in the present invention.

1. Antibacterial activity

As shown in the Examples, the anticariogenic and antiperiodontitic products of the present invention effectively depress or inhibit the growth of S. mutans which causes dental caries and Bacteroides which causes periodontitis.

Nevertheless, the products have selective and specific antibacterial spectra; that is, the products have substantially no inhibitory effects on the growth of the major lactic acid bacteria (S. faecalis, S. faecium, L. fermentum, L. acidophilus, B. adolescentis, B. infantis, B. bifidum, and B. breve) and E. coli of the intestinal bacteria.

2. Acute toxicity

As shown in the Examples, an LD50 value of the hot water-soluble extracts or the sterilized bacterial cells according to the present invention was >ca. 6 mg/mouse (intraperitoneal administration). Both the preparations according to the present invention were substantially nontoxic on oral administration.

The anticariogenic and antiperiodontitic products of the present invention can be practically used in the forms of, for example, tooth-paste, gargles, troches, chewing gum, and the like, and in the form of various kinds of anticariogenically and antiperiodontitically depressive and preventive foods and beverages added with the anticariogenic and antiperiodontitic products. The amount used in practical use is ca. 0.001% to 10% (w/w) in the form of the dried treated bacterial cells or the hot water-soluble extracts.

The present invention will now be further shown by, but is by no means limited to, the following Examples.

The lactic acid bacterial strains of the present invention were inoculated into 1000 parts by volume of Rogosa broth medium at a final concentration of 10.sup.6 viable cells/ml, and were stationarily incubated at 37.degree. C. for 15 to 24 hours. Then, the bacterial cells were collected by centrifugation of the culture fluid. The separated cells were washed twice with 20 parts by volume of 0.85% NaCl solution by centrifugation. The centrifuged cells were then suspended in 1 part by volume of distilled water, and were autoclaved at 115.degree. C. to 121.degree. C. for 10 to 15 minutes. Finally, the autoclaved cells were centrifuged to obtain the supernatant, and the supernatant was lyophilized or heat-dried at 110.degree. C. This dried extract was used for the growth inhibition tests.

The sterile solution of this extract (the extract was dissolved in water, the pH was adjusted to 7, and sterilization was done by autoclaving at 121.degree. C. for 15 min or filtration with membrane filters) was added into the sterile Rogosa broth or Todd-Hewitt broth (note 1) together with sterile distilled water to adjust the concentration of the medium to one half and to adjust the concentration of the hot water-soluble extract. To this medium, S. mutans 8148 (supplied from the National Institute of Health, Japan) was inoculated at the viable cell concentration of 10.sup.6 /ml. The viable cell number was enumerated periodically, for 0 to 24 hours after inoculation. In the controls, 0.85% NaCl solution was added instead of the extract.

Dissolve 30 grams/liter distilled water of powder containing the following formula.

The concentration of the hot water-soluble extracts in the extraction fluid is shown in Table 6.

As summarized in FIGS. 1 to 5, the inhibitory effect of the hot water-soluble extracts on the growth of S. mutans depended on the concentration of the extracts, in any strain of Streptococcus faecium, Streptococcus equinus, Lactobacillus fermentum, and Lactobacillus salivarius. The hot water-soluble extracts obtained from the S. faecium strain inhibited the growth of S. mutans completely for 24 hours, almost completely for 12 hours, and >95% for 12 hours at 2%, 1%, and 0.5% of the extracts, respectively. The hot water-soluble extracts obtained from S. equinus strain completely inhibited the growth of the S. mutans strain for 24 hours at 1% of the extracts, and the 2% concentration of the extracts showed a weak bactericidal effect on S. mutans. The hot water-soluble extracts obtained from the L. fermentum strain had a bactericidal effect on S. mutans at >2.5% of the extracts. The hot water-soluble extracts obtained from the L. salivarius strain inhibited completely the growth of S. mutans for 24 hours at 2.5% of the extracts, and inhibited >95% at 1.5% of the extracts. The influence of the hot water-soluble extracts obtained from these lactic acid bacteria on the cell division rate of the S. mutans strain is shown in Table 7. The hot water-soluble extracts greatly reduced the cell division rate at a concentration at which the extracts did not completely inhibit the growth.

The heat-treated whole cells and the other preparations of the present invention showed the same results as described above. In FIGS. 1 to 5, the ordinate indicates viable cell counts (log/ml) of S. mutans, the abscissa indicates the incubation time (hours), and the bacterial species are shown by initials.

The pre-reduced GAM broth medium (*) or VLG broth medium(**) containing hot water-soluble extracts obtained by the method described in Example 1 was inoculated by B. gingivalis AD50001 at the concentration of 10.sup.7 /ml under an anaerobic condition, and was incubated at 37.degree. C. The growth (turbidity of the culture) after 24 hours was as shown in Table 8. These results indicate clearly that the growth inhibition of B. gingivalis by the hot water-soluble extracts from any strain of S. faecium, S. equinus, L. fermentum, and L. salivarius was dependent on the concentration of the hot water-soluble extracts added to the growth medium. The hot water-soluble extracts obtained from any strain of S. faecium, S. equinus, and L. salivarius completely inhibited the growth of B. gingivalis at a 3% concentration of the extracts for 24 hours. The hot water-soluble extract from L. fermentum almost completely inhibited the growth at a 5% concentration for 24 hours.

The growth inhibition of B. intermedius AD50002 and B. fragilis RIMD 0230001 by the hot water-soluble extracts was examined (Table 9). The experimental methods were the same as in Example 1. The concentration of the extract added was 3.0%.

B. intermedius may cause juvenile and acute periodontitis, but B. fragilis may have no relation to the disease. The hot water-soluble extracts obtained from any strain of S. faecium, S. equinus, L. salivarius, and L. fermentum inhibited the growth of B. intermedius (Table 9). However, the extracts did not inhibit the growth of B. fragilis, but this does not cause periodontitis.

Equal volumes of blood defibrinated and diluted 30-fold with saline, the bacterial cell suspension (ca. 2 of optical density) of B. gingivalis or B. intermedius, and the hot water-soluble extracts of the present invention were mixed on slide glasses, and the hemagglutination and time to agglutinate were observed (Table 10).

Hemagglutination is thought to be related to the adherence of bacteria to the gingivae, etc. The hot water-soluble extracts obtained from any strain of S. faecium, s. equinus, L. salivarius, and L. fermentum inhibited the hemagglutination, suggesting that the extracts may inhibit the adherence of Bacteroides to the gingivae, etc.

The influence of the hot water-soluble extracts obtained from the respective lactic acid bacteria of the present invention on the intestinal lactic acid bacteria and E. coli is summarized in Table 11. The concentration of the extracts was 3.0% in the test medium. The results show that the hot water-soluble extracts of the present invention have no influence on the major human intestinal bacteria.

(i) The hot water-soluble extracts prepared according to the above-mentioned preparation methods were intraperitoneally administered into ICR mice (6 week-old, male, average body weight 31.0.+-.0.6 g) in the form of an 0.5 ml saline solution containing the extracts corresponding to 9.times.10.sup.9, 9.times.10.sup.8, or 9.times.10.sup.7 bacterial cells/mouse (10 mice in each group). The thanatobiological observation of the mice was carried out for 14 days.

The LD50 values (mg/mouse) calculated according to a Behrens-Karber method are shown in Table 12. All the strains tested of the present invention were substantially nontoxic in the case of daily oral administration.

(ii) The heat-treated dead cells prepared according to the above-mentioned preparation methods were intraperitoneally administered into ICR mice (6 week-old, male, average body weight 30.0.+-.0.7 g) in the form of the dead bacterial cell suspension in 0.5 ml saline containing the extracts corresponding to 9.times.10.sup.9, 9.times.10.sup.8, and 9.times.10.sup.7 cells/mouse (10 mice in each group). The thanatobiological observation of mice was carried out for 14 days.

The LD50 values (bacterial cell number/mouse) of the lactic acid bacterial strains, calculated according to a Behrens-Karber method, were 6.times.10.sup.13 cells/mouse (intraperitoneally), and all the strains were substantially nontoxic in the case of daily oral administration.

1. Tooth-paste

2. Gargles

3. Chewing gum

4. Anticariogenic and antiperiodontitic foods and beverages

The heat-treated dead cells or the hot water-soluble extracts of the present invention can be used for anticariogenic and antiperiodontitic foods and beverages by the addition of 0.001% to 10% (dry weight) of the preparations into bread, cookies, candies, yogurt, fruit juice, tea, coffee, and other general foods and beverages.