Oral hygiene and the prevalence of oral group D streptococci in medically-physically compromised and periodontal disease patients.

The relationship between oral hygiene and oral Group D streptococcal carrier status was examined in two groups of dental clinic patients. Eighteen medically-physically compromised and 20 periodontitis patients were selected for study. Oral hygiene status was assessed and the prevalence of oral Group D streptococci was determined by sampling the oral cavity with a vigorous 15 second rinse with 5 ml peptone-saline solution. Three ml of each sample was cultured at 40 degrees C in 30 ml of SF broth for 72 hours. Esculin fermenting colonies isolated from the SF broth were characterized biochemically according to standardized procedures and patients were classified as either carriers or non-carriers. Group D streptococci were detected in 27.8% of the medically-physically compromised group and 4.5% of the periodontal disease patients. The mean DI-S score of the medically-physically compromised group was significantly lower than in the periodontal group. Within the medically-physically compromised group, the DI-S means of carriers and non-carriers were not significantly different. The data indicated no important relationship between oral hygiene and the prevalence of oral Group D streptococci in the groups studied.

Effect of continuous fluoride gel use on plaque fluoride retention and microbial activity.

Twelve consecutive wk of daily five-minute topical applications of 1% NaF gel by non-cancer control subjects did not significantly affect plaque concentrations of Streptococcus mutans or Lactobacillus spp. Plaque F- levels increased 150% (P less than .001), while production of acetate and lactate decreased 40% (P less than .007) and 66% (P less than .001), respectively. Long-term (12 wk to more than five yr) fluoride gel use by post-irradiation xerostomic cancer patients was associated with increases in plaque F- and decreases in acidogenesis similar to those observed in the control subjects. Plaque concentrations of cariogenic organisms increased during the first yr of radiation-induced xerostomia and fluoride gel use, before starting to decline. Although sustained fluoride treatment increased (P less than .001) the ratio of fluoride-resistant to fluoride-sensitive strains, the number of patients harboring detectable S. mutans was diminished (P less than .001).

Characterization of calcifiable proteolipid from Streptococcus mutans.

Proteolipid is known to initiate calcification in vitro. Apoprotein and phospholipid components of proteolipid from five of 14 calcifiable S. mutans specimens were characterized. The apoproteins contained 16 amino acids with calculated percent polarities ranging from 32.0 to 45.2. The acidic phospholipids were cardiolipin, mono- and diphosphoinositides, and phosphatidylserine. Neutral lipids, phosphatidylethanolamine and phosphatidylcholine, were also found. The latter were the most abundant in all isolates. Appropriate hydrophobic proteins and acidic phospholipids in the proteolipids accounted for S. mutans calcifiability.

Calcifiability comparison among selected microorganisms.

Seven ATCC strains of bacteria were examined for apatite formation in a chemically-defined calcification-supporting medium and also in a metastable calcium phosphate solution. One, E. coli, calcified in both. One, S. aureus, calcified in the solution, but not in the medium. The other five did not calcify in either. The results substantiate the belief that calcification is restricted to certain microorganisms. However, they do not rule out the possibility that a noncalcifiable microorganism has the potential to calcify, and the activity is prevented by a cell component. Additionally, the findings emphasize that determining microbiologic calcifiability only in a calcification-supporting culture medium is inadequate. In culture, an efficient calcium pump might preclude calcification by establishing a cytoplasmic calcium level too low for nucleation activation. Calcifiability assays should be done by incubating minimally-metabolizing freeze-dried cells in metastable calcium phosphate solution.

Effects of a single application of sodium fluoride gel on dental plaque acidogenesis.

Quantitative comparisons of the lactate and acetate produced by human dental plaque in vitro and in situ were made before and after five-minute exposures to 1% NaF gel. Assays included total ionic plaque fluoride by a fluoride electrode, L(+)- and D(-)-lactate by an enzyme method, and acetate by a standard GLC procedure. A single topical application of NaF gel increased plaque fluoride about eight-fold. Six hours after gel use, plaque fluoride had declined to about 20% above pretreatment levels. Plaque fluoride baseline levels and variation between and within subjects were greater than expected. This may have been due largely to non-standardized oral hygiene practice and/or the routine use of fluoride dentifrices and the wide variation in the natural fluoride content of drinking water. Fluoride gel use significantly reduced L(+)-lactate in vitro, but D(-)-lactate and acetate were virtually unaffected. Conversely, gel use significantly inhibited the in situ production of each of these acids. The findings of this study indicate that topically applied fluoride gel impairs plaque acidogenesis to an extent that could be meaningful in preventing dental caries.

Fluoride resistance and adherence of selected strains of Streptococcus mutans to smooth surfaces after exposure to fluoride.

The fluoride resistance and smooth surface adherence characteristics of Streptococcus mutans were examined using tooth model and radioactive cell assays. Resistance to 600 ppmF by S. mutans isolated from the plaque of radiation-induced xerostomia patients receiving daily topical applications of a caries preventive 1% NaF gel was transient. Resistance induced in vitro in two strains of S. mutans by exposure to gradually increasing levels of NaF was apparently permanent. Smooth surface adherence by both fluoride-sensitive and -resistant strains of S. mutans 6715 in a tooth model system was slightly diminished by 1% NaF gel. Fluoride-resistant strains retained 89 to 93% of their adherence capability in 600 ppmF, as determined by the cell radiolabeling assay.

Effect of sodium fluoride on the viability and growth of Streptococcus mutans.

A fluoride-sensitive (FS) strain of Streptococcus mutans and a laboratory-induced fluoride-resistant (FR) offspring were compared for the effects of sodium fluoride on viability and growth. There was a significant fluoride-related loss of viability in resting cell suspensions of the FS strain during a 47-hour exposure to fluoride levels above 75 ppm that was not encountered with the FR strain. The addition of 300 ppmF to actively growing six-hour broth cultures almost totally arrested the growth of the FS strain, while only slightly reducing that of the FR culture. The addition of 600 ppmF immediately terminated FS growth, and greatly reduced the rate and maximum growth of FR cultures.

Calcification of selected strains of Streptococcus mutans and Streptococcus sanguis.

Nine strains of cariogenic Streptococcus mutans and two strains of Streptococcus sanguis were tested for their ability to form hydroxyapatite. The cells were examined by X-ray diffraction and electron microscopy for apatite crystals after growth in a synthetic calcification medium. Each of the test isolates, except for one strain of S. sanguis, produced intracellular mineral. Two strains of S. mutans formed both intra- and extracellular crystals. There was no apparent relationship between calcifiability and serotype.

Calcification by Escherichia coli.

Escherichia coli K-12, grown in a synthetic medium containing metastable calcium phosphate, formed intracellular biological apatite crystals.

Isolation of Bacillary and Streptococcal Variants from Bacterionema matruchotii.

Bacterionema matruchotii, an oral filamentous organism, dissociated to form unusual flat colonies. Subculture of the flat colonies, composed of diphtheroids, yielded pure cultures of bacillary and streptococcal variants.