Naeslundii Strains Research Articles

Glycogen synthetic and degradative activities by Actinomyces viscosus and Actinomyces naeslundii of root surface caries and noncaries sites.

The relative glycogen synthetic and degradative activities of Actinomyces viscosus and Actinomyces naeslundii, freshly isolated from root surface caries and noncaries sites, were compared. The glycogen synthetic activity was measured by incubating glucose-(or sucrose-)grown resting cells with 100 mM glucose (or sucrose) and U-[14C]-glucose (or U-[14C]-sucrose) on a pH-stat maintained at 5.0, 6.0, and 7.0 for 1 h under anaerobic conditions. For the glycogen degradation assays, after the 1-hour incubation period, the cells were reincubated under similar conditions, but in the absence of external carbon sources. Carbohydrate utilization and total acid formation were also monitored. Both the glucose- and sucrose-grown cells of A. viscosus and A. naeslundii strains originating from root surface caries lesions synthesized approximately twice as much glycogen as the strains of noncaries origin. Although there were significant differences in the rates of glycogen synthesis, the rates of glycogen degradation were essentially the same for the Actinomyces strains from both caries and noncaries sites. However, the time required for glycogen degradation by the strains from caries sites was much longer. This study suggests that the abilities of A. viscosus and A. naeslundii originating from root surface caries lesions to synthesize large amounts of glycogen and to degrade this stored polymer slowly under conditions of starvation, particularly in an acidic environment, may be one of the factors contributing to the cariogenic potential of these organisms in root surface caries.

Glycogen synthetic abilities of Actinomyces viscosus and Actinomyces naeslundii freshly isolated from dental plaque over root surface caries lesions and non-carious sites.

Relative glycogen synthetic abilities of resting cells of fresh clinical isolates of Actinomyces viscosus and Actinomyces naeslundii originating from dental plaque samples over root surface caries lesions and non-carious sites were studied under anaerobic conditions at a constant pH of 7.0, with U-(14C)-glucose used as the carbon source. Although the rates of glucose utilization and total acid formation were essentially the same, A. viscosus strains isolated from root surface caries lesions showed glycogen synthetic abilities approximately two to seven times higher than did A. viscosus strains originating from non-carious sites, and also two to four times higher than did A. naeslundii strains originating from both carious and non-carious sites.

Isolation and characterization of coaggregation-defective mutants of Actinomyces viscosus, Actinomyces naeslundii, and Streptococcus sanguis.

Spontaneously occurring coaggregation-defective (COG-) mutants of oral actinomycetes and streptococci were isolated and used to study interactions between cells of these two kinds of bacteria. COG- mutants of each kind of bacteria were isolated by a simple enrichment scheme. Parent strains were mixed with a coaggregating partner strain, coaggregated cells were removed by low-speed centrifugation, and non-coaggregated cells were recycled by the addition of more partner strain cells. COG- mutants constituted up to 10% of the parent strain cell type in the final enriched cell suspension. Unlike their respective parent strains, COG- mutants of Actinomyces viscosus T14V and Actinomyces naeslundii ATCC 12104, and A. naeslundii I exhibited no lactose-reversible coaggregation with certain oral Streptococcus sanguis strains. However, these COG- mutants were not altered in their coaggregations with another S. sanguis strain, H1, a member of a streptococcal coaggregation group that exhibits only lactose-nonreversible coaggregations with oral actinomycetes. Although all coaggregations between S. sanguis H1 and these actinomycetes appear to be alike, examination of a COG- mutant of S. sanguis H1 revealed that, like its parent, it coaggregated with A. viscosus T14V and its COG- mutants, but unlike its parent, it did not coaggregate with the two A. naeslundii strains or their COG- mutants. Thus, it was concluded that at least two types of surface components are important in mediating coaggregation between S. sanguis H1 and actinomycetes. The COG- mutant of S. sanguis allowed detection of these components, which were indistinguishable in previous studies.

Development of a selective medium for detection and enumeration of Actinomyces viscosus and Actinomyces naeslundii in dental plaque.

A selective medium (CFAT) was developed for the detection and enumeration of Actinomyces viscosus and Actinomyces naeslundii in dental plaque. Neutral acriflavin and potassium tellurite were used in combination with the known selective agents cadmium and fluoride to eliminate most of the competing plaque flora. Composition of CFAT per liter was as follows: Trypticase soy broth (BBL Microbiology Systems), 30 g; glucose, 5 g; agar, 15 g' cadmium sulfate, 13 mg; sodium fluoride, 85 mg; neutral acriflavin, 1.20 mg; potassium tellurite, 2.50 mg; basic fuchsin, 1.25 mg; defibrinated sheep blood, 50 ml. A. viscosus reference strains of human origin grew on CFAT without reduction in numbers under an atmosphere of 90% air-10% CO2. Animal strains of A. viscosus were inhibited at the level of cadmium in CFAT. Two of six A. naeslundii strains did not grow on CFAT. Improved recovery of A. viscosus and A. naeslundii from dental plaque occurred on CFAT, as compared with two other selective media which contained either cadmium sulfate or sodium fluoride, respectively, as selective agents. CFAT was more selective with regard to much of the extraneous gram-positive flora. Bacterionemia, Neisseria, yeasts, and streptococci were virtually eliminated.

Deoxyribonucleic Acid Hybridization Among Strains of Actinomyces viscosus and Actinomyces naeslundii

Deoxyribonucleic acids (DNA) were extracted from strains of Actinomyces viscosus and Actinomyces naeslundii and were compared by DNA-DNA hybridization. When their DNAs were compared by hybridization on membrane filters, A. viscosus strains from humans were barely separable from A. naeslundii strains, but A. viscosus strains from hamsters were distinctly different. A. viscosus strains from veterinary infections were identical to human strains. With the use of the more sensitive S1 nuclease hybridization method with DNA from a set of strains that had been used in a numerical taxonomy study, typical A. viscosus strains from humans could be distinguished from typical A. naeslundii strains. A group of atypical A. naeslundii strains could also be delineated. The results generally parallel the taxonomic divisions of these organisms based on serology or numerical taxonomy. A. viscosus strains from humans and A. naeslundii strains are similar but distinguishable, but A. viscosus strains from hamsters are clearly separable.

The natural history of periodontal bone loss in germfree and gnotobiotic rats infected with periodontopathic microorganisms.

A new technique for evaluating the vertical component of bone loss in rats is described in which silicone base impression material is utilized. The extent and pattern of bone loss in germfree rats is compared to the bone loss in gnotobiotic animals infected with either Streptococcus mautans strain 6715 or with Actinomyces naeslundii strain I or with Actinomyces viscosus strain T 14. In general, after approximately 60 days of infection the gnotobiotic animals demonstrated patterns of bone loss similar to germfree animals although the extent of loss was more marked. The major increases in bone loss (both horizontal and vertical) were observed in the period between 60 and 90 days of infection. The major destruction offurs on the lingual aspects of maxillary molars. Vertical bone loss was greater in A. naeslundii infected animals than in S. mutans infected animals.

Interbacterial aggregation of Actinomyces naeslundii and dental plaque streptococci.

The ability of human Actinomyces naeslundii strains to aggregate with dental plaque streptococci was found to be strain specific. A. naeslundii strains aggregated strongly more often with specific strains of Streptococcus sanguis and Streptococcus mitis than with Streptococcus mutans strains. The effects of proteolytic enzymes and heat on the interbacterial affinities of A. naeslundii 398A and S. sanguis S, two strains which were found to aggregate strongly, were studied. Enzyme or heat treatment of 398 A, but not S. sanguis S, impaired aggregation. Electron microscopic examination of aggregates of untreated bacteria revealed that the attachment between cells of strains 398 A and S was mediated by short tufts of electron‐dense fuzzy components of the cell surfaces. The affinity between cells of A. naeslundii and the streptococci which readily colonize cleaned smooth tooth surfaces may account, in part, for the previously‐reported, delayed increase in A. naeslundii proportions among bacteria forming early plaque deposits.

Differentiation of Actinomyces propionicus from Actinomyces israelii and Actinomyces naeslundii by gas chromatography.

Gas–liquid chromatography (g.l.c.) was used for the analysis of certain metabolic end products of Actinomyces propionicus, as an aid in the separation of this organism from the morphologically similar Actinomyces species, A. israelii and A. naeslundii. Profiles of the chromatograms for the major volatile acids of five strains of A. propionicus studied were found to be distinct from those of four strains of A. israelii and four strains of A. naeslundii. The ratio of propionic acid to acetic acid was approximately 50 times as great for A. propionicus as for the other Actinomyces species. Formic acid was present in significant amounts in both A. israelii and A. naeslundii, but was present only in trace amounts in A. propionicus.Two major nonvolatile acids, lactic and succinic, were identified for the A. israelii and A. naeslundii strains. One of the A. propionicus strains also showed both acids in significant amounts; however, the other four strains of A. propionicus showed succinic acid in large amounts, but only trace amounts of lactic acid.