Immunoelectron microscopic studies of Actinomyces viscosus

Actinomyces naeslundii in initial dental biofilm formation

The combined use of confocal laser scanning microscopy (CLSM) and fluorescent in situ hybridization (FISH) offers new opportunities for analysis of the spatial relationships and temporal changes of specific members of the microbiota of intact dental biofilms. The purpose of this study was to analyse the patterns of colonization and population dynamics of Actinomyces naeslundii compared to streptococci and other bacteria during the initial 48 h of biofilm formation in the oral cavity. Biofilms developed on standardized glass slabs mounted in intra-oral appliances worn by ten individuals for 6, 12, 24 and 48 h. The biofilms were subsequently labelled with probes against A. naeslundii (ACT476), streptococci (STR405) or all bacteria (EUB338), and were analysed by CLSM. Labelled bacteria were quantified by stereological tools. The results showed a notable increase in the number of streptococci and A. naeslundii over time, with a tendency towards a slower growth rate for A. naeslundii compared with streptococci. A. naeslundii was located mainly in the inner part of the multilayered biofilm, indicating that it is one of the species that attaches directly to the acquired pellicle. The participation of A. naeslundii in the initial stages of dental biofilm formation may have important ecological consequences.

An immunohistochemical study on the localization of Porphyromonas gingivalis, Campylobacter rectus and Actinomyces viscosus in human periodontal pockets

The localization and distribution of Porphyromonas gingivalis, Campylobacter rectus and Actinomyces viscosus were studied in human periodontal pockets. After obtaining voluntary consent from 9 patients, 12 teeth and their surrounding periodontal tissue with advanced adult periodontitis were extracted carefully so as not to change the structure of the periodontal pockets. The specimens were processed into serial sections. One of the sections was stained with Brown & Brenn-modified Gram stain to observe the distribution of bacteria. The others were stained immunohistochemically by the Labelled Streptavidin Biotin method (LSAB method) using specific rabbit antibodies against selected bacteria. Some bacteria could be found within epithelial cells. P. gingivalis was found in 9/12 of the samples examined. Small aggregates of P. gingivalis were scattered in all parts of the periodontal pockets, and some of these aggregates could be seen in close contact with the epithelium. Conversely, C. rectus was observed in 5/12 of the samples examined and was predominantly located in the middle and deep pocket zones. C. rectus tended to form large clumps in both the tooth-attached and epithelium-associated plaque area. A. viscosus was observed in 7/12 of the samples examined and was localized predominantly in the tooth-attached plaque area, especially in the shallow and middle pocket zones. Although unexpected spills of unattached plaque from periodontal pockets was possible, immunohistochemical staining with species-specific antibodies was extremely sensitive and revealed the localization and the distribution of periodontal disease-associated bacteria in human periodontal pockets.

Electron immunocytochemical localization of Actinobacillus actinomycetemcomitans leukotoxin

The Actinobacillus actinomycetemcomitans leukotoxin was localized in A. actinomycetemcomitans bacteria using an electron immunocytochemical thin-section labeling method. An immuno-dot blot procedure was initially used to ascertain the optimal specimen fixation. This consisted of a periodate-lysine-paraformaldehyde (2%) fixative in a phosphate buffer followed by embedding in LR White. Affinity-purified toxin was used to produce a monospecific polyclonal antibody. The reaction sites were visualized with a colloidal gold-tagged reporter antibody. The leukotoxin was found to be localized either in the cell envelope and/or in membranous vesicles on the outer surface of the bacterial cell. These results support previous observations indicating the same location.

Transmission electron microscopy of early microbial colonization of human enamel and root surfaces in vivo

This study describes the early microbial colonization of teeth by the use of light- and transmission electron microscopy. Six dental students carried a total of 60 test pieces of unerupted enamel and root surface in intraoral acrylic appliances for 4, 8, 12, 24 and 48 h, during which periods oral hygiene was abandoned. Pronounced variations were recorded in structure and thickness of the pellicle across the individual surfaces of both dental tissues. Bacterial single-cell colonization increased the electron density of the adjoining pellicle. Micro-colonies of bacteria were observed in relation to enamel surface irregularities such as perikymata, while the distribution on root surfaces appeared incidental. Root surfaces were generally colonized by thicker deposits than homologous enamel surfaces although the structural composition of the microbiota was similar. Gram-positive bacteria with thick cell walls appeared in coccoid or rod-shaped configurations depending on the age of the bacterial deposit. These bacteria were further characterized by selective invasion between collagen fibers. After 48 h the complexity of the microbiota was increased by the establishment of new bacterial species in the superficial layer. It is concluded that the pattern and composition of the early microbiota on teeth is more complex and variable than hitherto assumed.

Assignment of Actinomyces viscosus and Actinomyces naeslundii strains to numerical taxonomy clusters by immunofluorescence based on antifibril antisera

A previous observation, using a few representative laboratory strains, that rabbit antisera raised against isolated surface fibrils might be useful in identifying Actinomyces viscosus and Actinomyces naeslundii isolates to their correct numerical taxonomy clusters was reexamined with a large culture collection, including clinical isolates from three different laboratories. Strains were first identified by a slower standard procedure, including agglutination with anti-whole-cell antisera, catalase test, and gas and paper chromatography as needed. Indirect immunofluorescence tests indicated that antisera raised against fibrils of strains representing the three principal taxonomic clusters could separate most strains into their correct clusters. The antisera were particularly successful in separating two taxonomically distinct groups of A. naeslundii, clusters 3 and 5, but could not separate A. viscosus belonging to the principal cluster (no. 1) and minor clusters (no. 2, 4, 6).

Immunoelectron microscopic study of Actinomyces colony in odontogenic periapical infection

A periapical Actinomyces colony was studied by immunoelectron microscopy with a specific antiserum against Actinomyces israelii. Positive as well as some negative micro-organisms were seen within the colony. Reacting antigens were localized in the cytoplasm and the cell wall of the bacteria, which suggests that more than one antigen is involved in the reactions with the present antiserum. The ultrastructural results confirmed the applicability of the peroxidase method with Actinomyces antiserum in paraffin sections for diagnostic purposes.

Immunoperoxidase labeling of Streptococcus mutans for scanning electron microscopy

The application of an immunoperoxidase method to labeling of Streptococcus mutans subsp. sobrinus for scanning electron microscopy is described. Bacteria from four separate cultures were fixed in 2.5% buffered glutaraldehyde solution. The specimens were treated in accordance with an indirect immunolabeling procedure using a rabbit anti-S. mutans subsp. sobrinus gamma-globulin. Labeled bacteria were equipped with a layer of small, distinct globules of horse-radish peroxidase reaction product. Bacteria exposed to control incubations were not equipped with this layer.