R.J. Fitzgerald

Human Saliva as a Nitrogen Source for Oral Streptococci

The ability of human saliva supernatant to support the in vitro growth of Streptococcus mutans and Streptococcus sanguis was examined. Saliva s

Specificity of utilization of human salivary proteins for growth by oral streptococci.

Mixed salivary proteins, obtained by fractional ultrafiltration of centrifuged human saliva were utilized by Streptococcus mutans or Streptococcus sanguis as sour

Basic Biological Sciences Cariogenicity of Human Oral Lactobacilli in Hamsters

Of 50 strains of lactobacilli isolated from dental plaque of school children, two strains, provisionally identified as Lactobacillus salivarius, and one strain, provisionally identified as Lactobacillus fermentum, induced significant caries activity in conventional hamsters. Sucrose was a required dietary cariogenic substrate and could not be replaced with glucose or starch. In contrast to cariogenic strains of Streptococcus mutans the active lactobacilli did not form adherent sucrose-mediated plaques in vitro, did not form intracellular iodophilic polysaccharides and did not form detectable insoluble extracellular polyglucans.

Differential Utilization of Proteins in Saliva from Caries-active and Caries-free Subjects as Growth Substrates by Plaque-forming Streptococci:

Mixed or parotid saliva from caries-active individuals consistently supported better growth of Streptococcus mutans (type c) than that from caries-free individuals. Electrophoretic studies revealed that certain proteins in caries-active salivas were susceptible to microbial attack, but similar proteins in caries-free salivas were refractory.

Comparative Growth Responses of Oral Streptococci on Mixed Saliva or the Separate Submandibular and Parotid Secretions from Caries-active and Caries-free Individuals

Growth of S. mutans on mixed or parotid saliva from CF individuals may be influenced by the availability of growth-supportive proteins or the inhibitory activity present in parotid saliva. A deficiency in growth-supportive proteins may explain the limited growth of S. sanguis on mixed or submandibular saliva from these individuals.

Caseinolytic and Glyoprotein Hydrolase Activity of Streptococcus mutans

After the sonic rupture of Streptococcus mutans cells, two fractions were obtained. The soluble cell contents hydrolyzed casein but not porcine gastric glycoprotein. The cell-debris fraction showed proteolytic activity on both casein and gastric glycoprotein. Glycoprotein hydrolase activity also was demonstrated in the medium from which the cells were harvested.

Utilization of Hydroxyapatite Adsorbable Salivary Proteins as Growth Substrates for Plaque-forming Oral Streptococci

Hydroxyapatite-treated clarified mixed saliva showed a marked reduction in growth-supportive activity for Streptococcus mutans. Isoelectrophoretic analysis revealed that proteins specifically attacked by S. mutans were among those adsorbed by HA. The proteins desorbed from HA-supported growth of S. mutans at levels comparable to untreated saliva.

Comparative Cariogenicity of Streptococcus mutans Strains Isolated from Caries Active and Caries Resistant Adults

The presence of Streptococcus mutans in dental plaque is generally associated with initiation and development of caries at that site unless some protective mechanism intervenes. For example, LOESCHE, W. et al. (Inf and Immun 11: 252, 1965) found high S mutans levels in caries-free children who had been exposed to fluoridation. However, some rare individuals have enjoyed lifelong freedom from caries despite the absence of any such obvious measures as fluoridation that would tend to prevent this disease and despite the abundant presence of S mutans in their dental plaques (GAFFAR, A. et al., J Dent Res 52: 173 [abstract] 1973). One possible explanation for the caries resistance of such individuals is that the S mutans strains which they harbor have lost their virulence. In order to investigate this possibility, we compared the cariogenicity of S mutans strains isolated from caries resistant and susceptible adults in a hamster test system. The caries resistant subjects were adults who had exhibited positive plaque counts of S mutans for several years prior to this study (GAFFAR, et al., ibid). None of them had been born in a fluoride area and there was nothing in their diet, oral hygiene or fluoride exposure to account for the absence of caries. The three caries resistant individuals had a DMF score of zero; the three caries active subjects had a DMF score of 10 or more including open lesions at the time of the study. Plaque counts of S mutans were comparable in the two groups. Plaque suspensions at various dilutions were grown on the selective medium of GOLD et al. (Arch Oral Biol 18: 1357, 1973). Typical strains of S mutans were isolated and typed serologically (BRATTHALL, Odont Revy 21: 143, 1970) and by the biochemical scheme of SHKLAIR and KEENE (Arch Oral Biol 19:

Intermittent sucrose feeding and caries in hamsters

SEVERAL studies have compared the effects of sucrose and other carbohydrates on caries activity in rats receiving modifications of cariogenic diet 2000 of KEY= and JORDAN (1964) and it has been concluded that complete or intermittent replacement of dietary sucrose with other carbohydrates results in greater inhibition of caries on the molar smooth surfaces of rats than in the deep molar fissures (LARJE and LARSON 1970; FROSTELL, KEYES and LARSON, 1967; GUGGENHEIM et al., 1966). In the hamsters, where the predominant type of caries observed resembles smooth surface caries in rats, major reductions in caries have also resulted when sucrose was completely re-Because of the implied relationship between dietary sucrose and smooth surface caries activity in these test systems, it was desirable to determine the effects of intermittent substitution of sucrose with other carbohydrates on caries activity in the hamster since evidence of this particular aspect of the sucrose caries relationship in hamsters was not available. In the present study, glucose or corn starch was used as the sucrose substitute according to the schedule shown in Table 1. Theexperimentalfeeding programmes were started 7 days after weanling hamsters, 19-21 days of age, were infected orally with Streptococcus mutans strain Kl-R and provided with Diet 2000, which contained 56 per cent powdered sucrose, to facilitate implantation of Strep. mutans and initiation of plaque formation. One week prior to the termination of the experiment, oral swabs of 3 animals in each group were incubated overnight at 37°C in Todd-Hewitt broth and the cultures were examined by the fluorescent antibody technique (JABLON and ZINNER, 1966) for the detection of the following serotypes : Strep. mutans strains AHT, BHT and GS-5, which correspond to serologic groups a, b, and c of BRATTHALL (1970); Streptococcus sdivarius strain HHT and Actinomyces viscosus strain T-6. The study was terminated after 6 weeks of the experimental dietary programme and the defleshed jaws were stained with 5 per cent aqueous (w/v) Procion Brilliant Red 3 BNS (I.C.I. Organics, Providence, Rhode Island) according to ZINNER, DUANY and GOLAND (1971). Plaque extent was expressed as the number of molar surface units (KEYES, 1959) containing adherent deposits; caries was scored by the method of KEYES (1959). Table 1 shows that complete replacement of sucrose by glucose or corn starch after the first week of the experiment resulted in drastic reductions in caries scores in the 215 216 DOROTHEA B. FITZGERALD AND R. J. …

Streptococci of the Oral Cavity Other than Streptococcus mutans: An Evaluation of Some Present Knowledge

The inclusion in this symposium on cariogenic bacteria of a session devoted to oral streptococci otlier than Streptococcus mutans is evidence of the increasing concern of oral microbiologists about these organisms. Anyone who has studied the microbiology of the dental plaque is well aware that a variety of streptococci are present there, but very little is known yet of their significance in plaque ecology and pathogenicity. At least four types of nonmutans streptococci have been reported to induce caries in caries test systems for rodents. They are enterococci,1,2 S salivarius,2-5 sanguis,6,7 and S mitis (mitior) .8 In addition, the enterococci, S sanguis, and S mitior have frequently been implicated in subacute bacterial endocarditis, as has S mutans. Consequently, the four articles that make up this portion of the symposium are particularly important because of the information that they present on the most recent methods for identifying these often-encountered, but frequently neglected, organisms that have been relegated to the viridans group of streptococci.