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Hemagglutination by different Treponema denticola strains was observed for erythrocytes of human, horse, bovine, and rabbit origin. The growth of T. denticola ATCC 33520 in serum-free medium in continuous culture enabled us to study the hemagglutinating activity of freshly harvested spirochetes of a defined physiological status. The hemagglutinating activity was cell bound and not related to motility or appendages, such as fimbriae. The activity was destroyed by proteolytic enzymes, heat, and alkylation, indicating that the agglutinin is of a proteinaceous nature. In addition, periodate oxidation of the spirochetes indicated the involvement of carbohydrate groups. Microscopic inspection of the hemagglutination mixtures at the titration endpoints revealed that only a part of the spirochete population was involved in the hemagglutination process. The hemagglutinating activity was found to be growth phase related. The activity was blocked by serum, while of all tested amino acids and carbohydrates, only sialic acid blocked the activity at low concentrations. In conclusion, we found a hemagglutinating activity in T. denticola which was cell bound and growth phase related. The agglutinin may be a glycoprotein, like lectin, that recognizes sialic acid as a receptor.

The effect of bacteriocins produced by strains of Streptococcus mutans on the microbial composition of dental plaque was studied in gnotobiotic rats. In one set of tests, using S. mutans strains T2 and SW31, rats were simultaneously infected with the bacteriocinogenic parent (bac(+)) and corresponding bac(-) mutants, and the relative proportions of each strain present in three different tooth sites were determined at various time intervals after inoculation. Some animals were monoinfected with bac(+) and bac(-) strains, and in vivo properties, such as plaque fermentation end products, amount of plaque formed, and cariogenicity, were measured. In another series of tests with strains T2 bac(+) and T2 bac(-), animals were sequentially inoculated with a time interval of 1 week. On simultaneous inoculation, the bac(-) mutant, which was sensitive in vitro to the bacteriocin produced by the parent, was totally unable to establish in a plaque consisting of the bac(+) strain even when the challenging dose was increased 100-fold. In contrast, the bac(+) strain was successful not only in invading an established bac(-) plaque but also in eventually almost eliminating the mutant. In monoinfected animals, there were no significant differences in plaque-forming ability, fermentation end products, or cariogenicity between the two strains. Also, bacteriocin activity was detected in plaque harboring the bac(+) but not the bac(-) strain. The results not only indicate that bacteriocin activity can occur in vivo but also suggest that bacteriocinogeny might confer an ecological advantage upon a strain attempting to establish itself in an ecosystem.

Antibiograms with 20 different antimicrobial disks were studied for antibiotyping of Bacteroides gingivalis isolates. The stability of the antibiotypes was tested by passage in mice. Several B. gingivalis isolates of the same subject were used to investigate the presence of different antibiotypes in one individual, while isolates from different subjects were used to investigate individual differences. The antibiotypes were found to remain stable after animal passage. All tested strains of different origin represented different antibiotypes. The isolates from one subject all belonged to the same antibiotype. Principal component analysis of the data showed that two factors were important in the discrimination of the strains of B. gingivalis. One included beta-lactam antimicrobial agents that affect the cell wall. The other included antimicrobial agents that inhibit synthesis of protein and nucleic acid. Both principal component analysis and discriminant analysis proved to be of great use in the reduction of the amount of data and the visualization of the relations between different antibiotypes of B. gingivalis in a linear map. Among the investigated subjects, different antibiotypes of B. gingivalis were found, indicating that in the mouth of an individual, one antibiotype of B. gingivalis predominates and that different persons harbor different antibiotypes of B. gingivalis.

The present study shows adherence of Treponema denticola L12D and Treponema vincentii RitzA to guinea pig ear epithelial cells in vitro. The number of adhering organisms was positively related with the treponemal concentration and contact time. Incubation of washed T. denticola L12D and T. vincentii RitzA organisms or their culture supernatants with the epithelial cells induced morphological damage and detachment of these cells. In addition, indications for inhibition of epithelial cell proliferation were found. The activity of the supernatants was dose dependent, heat sensitive, and sensitive to sulfhydryl-containing components, suggesting the presence of enzymatic activity that might be of importance in the pathogenicity of these oral treponemes.

A test was developed to measure the keratinolytic activity of cutaneous and oral bacteria. Keratin, labeled with fluorescein isothiocyanate, was used in a phosphate buffer (pH 7.2) with 1 mM dithiothreitol. The degradation of keratin was estimated by measuring the fluorescence of the degradation products in the supernatant of the reaction mixtures in a luminescence spectrometer. Several oral and cutaneous bacteria were investigated: Bacteroides gingivalis, Bacteroides intermedius, Treponema denticola, Actinomyces odontolyticus, Staphylococcus epidermidis, Staphylococcus haemolyticus, Staphylococcus hominis, Staphylococcus saprophyticus, Brevibacterium epidermidis, Brevibacterium lines, Corynebacterium glutamicum, Corynebacterium minutissimum, Corynebacterium ovis, and Rhodococcus equi. The dermatophyte Trichophyton rubrum was used as a control organism. The test offered a simple and quantitative method for the estimation of keratin degradation and enabled us to show keratinolytic activity in Trichophyton rubrum, S. epidermidis, S. haemolyticus, B. linens, B. epidermidis, Bacteroides gingivalis, and Treponema denticola. The keratinolytic activity was cell bound and heat sensitive. The presence of dithiothreitol stimulated the degradation of keratin to mainly high-molecular-weight products.