Attachment of Bacteroides melaninogenicus subsp. asaccharolyticus to oral surfaces and its possible role in colonization of the mouth and of periodontal pockets

Haemolysis of human erythrocytes by the Fusobacterium nucleatum associated with periodontal disease

Fusobacterium nucleatum and Bacteroides gingivalis are associated with oral disease. They both attach to haemagglutinate and human erythrocytes. Experiments were performed to determine whether haemolysis would occur following attachment of strains of F. nucleatum and Bacteroides species including B. gingivalis. The F. nucleatum strains consistently displayed both haemagglutination and haemolytic activity. The B. gingivalis strains and other Bacteroides species displayed haemagglutination but no measurable haemolytic activity. Varying the concentration of the F. nucleatum whole cells in the standard haemolysis assay suggested a F. nucleatum-erythrocyte binding site interaction. The haemolytic moiety was observed in various cell, cell wall and lipopolysaccharide extracts.

Effect of decreased salivation and pH on the adherence of Klebsiella species to human buccal epithelial cells

To assess the role of reduced salivary flow and intraoral pH on gram-negative bacterial colonization of the oropharynx, we studied in vitro Klebsiella adherence to normal human buccal epithelial cells at various pH values and to buccal cells from patients with pathological xerostomia (decreased saliva flow). Reduced pH significantly increased adherence of Klebsiella pneumoniae 84 to normal buccal epithelial cells (P less than 0.001). In contrast, two clinical isolates of K. oxytoca showed no significant pH-dependent change in adherence. A corollary of this was that patients with pathological xerostomia had significantly increased adherence of K. pneumoniae 84 to their buccal epithelial cells as compared with normal controls (P less than 0.01). These results suggest that reduced salivary flow and the concomitant reduction of intraoral pH may predispose patients to bacterial colonization with K. pneumoniae.

Cell wall-associated protein antigens of Streptococcus salivarius: purification, properties, and function in adherence

Three cell wall-associated protein antigens (antigens b, c, and d) were isolated from mutanolysin-solubilized cell walls of Streptococcus salivarius HB and purified to apparent homogeneity by a combination of ion-exchange chromatography, gel filtration, and immunoadsorption chromatography. Antigens b and c were also isolated from culture supernatants. Antigen b consisted of more than 80% protein and had an apparent molecular weight as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of 320,000. Antigen c consisted of 57% protein, about 30% neutral sugar, and about 13% amino sugar, and its glycoprotein nature was confirmed by specific staining techniques. During sodium dodecyl sulfate-polyacrylamide gel electrophoresis antigen c resolved into two or more bands, depending on the source or the isolation procedure, in the molecular weight range from 220,000 to 280,000. Antigen d consisted of 95% protein and was observed in sodium dodecyl sulfate-polyacrylamide gel electrophoresis as two bands with molecular weights of 129,000 and 121,000. Under nondenaturing conditions all three antigens had molecular weights in the range from 1 x 10(6) to 3 x 10(6) as determined by gel filtration. The amino acid compositions of antigens b, c, and d were characterized by low amounts of basic amino acids and relatively high levels of nonpolar amino acids. Among oral streptococcal species antigens b and c were virtually restricted to strains of S. salivarius and most often to serotype I strains. Antigen b was recognized as the factor that mediates coaggregation of S. salivarius with Veillonella strains. The purified protein retained its biological activity. Antigen c could be linked to functions relating to adhesion of the streptococci to host tissues on the basis of its absence in mutant strains and blocking by specific antisera. The purified molecule had no detectable biological activity. Antigen d could not be linked to an established adhesion function.

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.

The effect of supragingival plaque control on the composition of the subgingival microbial flora in ligature-induced periodontitis in the monkey

The influence of supragingival plaque control on the subgingival microflora and clinical parameters of ligature-induced periodontitis in the Cynomolgus monkey was investigated. No clinical changes were observed during the six-week experimental period. The total cultivable flora and the proportions of total black-pigmented Bacteroides (BPB) and asaccharolytic black-pigmented Bacteroides decreased significantly in the cleaned test sites as compared to those in the non-cleaned controls. The study suggests that six wk of supragingival plaque control in the presence of periodontal disease may alter the periodontitis-associated microflora in the monkey, but not sufficiently to alter clinical signs of disease in this time period.

Oral implantation of Bacteroides asaccharolyticus and Eikenella corrodens in conventional hamsters

Oral implantation of Bacteroides asaccharolyticus 381-R' and Eikenella corrodens 1073S-R, which are highly resistant to streptomycin, was examined in conventional hamsters. The hamsters' first molars were ligatured with cotton threads preimmersed in bacterial suspensions. Bacterial inoculation was performed daily for 1 week, followed by a single weekly inoculation for 7 more weeks. Hamsters were fed Keyes' diet no. 2000 or ordinary powdered diet. Bacterial recovery, gingival histological changes, and immunological response were checked 2, 5, and 8 weeks after the daily serial inoculation. B. asaccharolyticus 381-R' was recovered from all hamsters during the experiment (6.7 X 10(6) to 6.3 X 10(8) colony-forming units). E. corrodens 10735-R was recovered from the hamsters fed Keyes' diet no. 2000 throughout the experimental period (2.4 X 10(5) to 1.2 X 10(6) colony-forming units), but not in the group fed the ordinary powdered diet. The histological changes in gingival tissues at the second week showed no differences among the control group, the B. asaccharolyticus-inoculated group, and the E. corrodens-inoculated group. However, by the eighth week, the inflammation persisted only in the bacteria-inoculated groups, especially in the B. asaccharolyticus-inoculated group. A relatively increased serum antibody titer was also observed in the B. asaccharolyticus-inoculated group, but not in the E. corrodens-inoculated group. These findings indicate that B. asaccharolyticus 381-R' and E. corrodens 1073S-R can be implanted in hamsters' oral cavity with the aid of cotton thread ligature. It was also suggested that B. asaccharolyticus may have some pathogenic role in the destruction of periodontal tissue in hamsters.

The effects of immunosuppressive drugs on periodontal inflammation in human renal allograft patients

The periodontal status of four kidney allograft patients was determined before and at periodic intervals for 9 months after receipt of the allografts. These patients received immunosuppressive drugs as part of their therapy, beginning at the time of transplantation. Three hemodialysis patients with analogous kidney disease and six eye patients who were otherwise healthy served as controls. Comparisons of plaque levels, pocket depths and gingival inflammation were made between the three groups of subjects. The results suggest that the administration of the immunosuppressive drugs significantly reduces the level of gingival inflammation in the presence of high levels of bacterial plaque. Pocket depths did not change significantly in eigher the allograft or control groups. Whole not conclusive, the findings support the hypothesis that host inflammatory and immunological responsiveness to plaque bacteria is a primary factor in the pathogenesis of destructive periodontal disease in humans.

Influence of sublethal antibiotic concentrations on bacterial adherence to saliva-treated hydroxyapatite

The influence of growth in the presence of sublethal concentrations of nine antibiotics on the ability of certain potentially odontopathic bacteria to attach to saliva-treated hydroxyapatite surfaces which mimic teeth was studied. Cells of Actinomyces viscosus LY7 and S2, Bacteroides gingivalis 381, Capnocytophaga ochraceus 6, and Actinobacillus actinomycetemcomitans N27 attached in lower numbers to saliva-treated hydroxyapatite when grown in the presence of 50% of the minimum inhibitory concentration of tetracycline. Electron microscopic observations of negatively stained preparations indicated that tetracycline-grown A. viscosus LY7 cells had fewer fimbriae than did untreated cells, which may account for the impaired ability of the treated cells to attach. However, cells of Actinomyces naeslundii L13 and S4 attached in higher numbers when grown in the presence of tetracycline, clindamycin, erythromycin, chloramphenicol, or neomycin. Streptococcus mutans strains H12 and JBP also exhibited increased adherence to saliva-treated hydroxyapatite when grown in the presence of 50 or 25% of the minimum inhibitory concentration of penicillin. Thus, growth in the presence of sublethal antibiotic concentrations could increase as well as decrease the adherence of bacteria to saliva-treated hydroxyapatite. Antibiotic-grown cells of the Actinomyces strains showed enhanced hemagglutination activity, but this did not correlate with their ability to attach to saliva-treated hydroxyapatite. Sublethal concentrations of antibiotics in the growth media also affected the coaggregation reactions of several organisms; the effects were specific for one member of the coaggregation pair.

Attachment of cell fragments of Fusobacterium nucleatum to oral epithelial cells, gingival fibroblasts and white blood cells

The characteristic haemagglutination (HA) caused by Fusobacterium nucleatum strains was used for measuring their attachment to oral epithelial, gingival fibroblast and white blood cells. Whole cells and sonicated preparations of oral F. nucleatum strains VPI No. 4355, 10197 and ATCC No. 10953 haemagglutinated human and sheep red blood cells. Sonicated preparations of the organisms were tested for HA activity before and after absorption with human cells. Buccal epithelial, gingival fibroblast and white blood cells bound the HA-active fragments, as observed by: (1) decrease in the HA activity of the sonicated preparation after absorption, (2) increase in HA activity of the cells used for absorption, (3) presence of microbial fragments on the cells after absorption detected by fluorescent antibody. The HA-active fragments were released from the cells by EDTA; furthermore, galactose but not glucose inhibited the attachment of F. nucleatum to human cells. The role of cell binding in colonization by the organisms and in immune-stimulated damage to host cells is important.

Role of interbacterial adherence in colonization of the oral cavities of gnotobiotic rats infected with Streptococcus mutans and Veillonella alcalescens

The role of interbacterial adherence in the colonization of the rate oral cavity was investigated with aggregating and nonaggregating strains of Veillonella alcalescens and Streptococcus mutans. V. alcalescens V-1 and S. mutans M-7 rapidly formed large stable aggregates when mixed in vitro. Aggregates could be reduced in size by sonication, but they could not be completely dispersed, indicating that bonding between the organisms was strong. V. alcalescens V-1 did not coaggregate with S. mutans C67-1, and V. alcalescens OMZ193 did not coaggregate with either S. mutans strain C67-1 or M-7. Osborne-Mendel rats monoassociated with either S. mutans C67-1 or M-7 were inoculated with veillonellae, molar teeth were removed at 2 h and at 14 days, and the number of veillonellae was determined. At 2 h post-inoculation there were 600 times as many colony-forming units of V. alcalescens V-1 adherent to the teeth of animals monoassociated with S. mutans M-7 when compared with animals monoassociated with the nonaggregating S. mutans C67-1. The number of colony-forming units of V. alcalescens V-1 was 1,000 times greater than the number of nonaggregating V. alcalescens OMZ193 in S. mutans M-7-infected animals. Similar results were obtained when teeth were samples 14 days after inoculation. Veillonellae inoculated into the mouths of germfree animals rapidly disappeared from tooth surfaces.

Eubacterium saburreum and Veillonella parvula: a symbiotic association or oral strains

A cocci-filament association was discovered in bacterial cultural studies of a subgingival plaque sample. Components were isolated and identified as Veillonella parvula and Eubacterium saburreum. A E. saburreum cell-associated material consisting of approximately 25% glucose and 70% protein was found which may play a role in the adherence of V. parvula to this filament. Acid end product analysis via gas liquid chromatography showed an uptake of lactic and succinic acids by V. parvula resulting in increased levels of acetic, propionic and n-butyric acids in mixed culture of the E. saburreum and the V. parvula strains. The ability of E. saburreum to adhere to nichrome wire and to glass surfaces as well as the secondary plaque forming ability of V. parvula indicates that these organisms may play a role in the maturation of human dental plaque.

The relation of keratinization to bacterial colonization on the baboon tongue as demonstrated by scanning electron microscopy

Scanning electron microscopic observations of the baboon tongue demonstrating specificity of microbial distribution as related to epithelial keratinization are presented. The number of bacteria inhabiting a surface was related to the degree of keratinization. Orthokeratotic dorsal tongue surfaces were most heavily colonized by bacteria. The parakeratotic and non-keratinized surfaces were less heavily populated, with non-keratinized areas showing the fewest numbers of bacteria.

Microbial surface interactions: reduction of the haemagglutination activity of the oral bacterium Fusobacterium nucleatum by absorption with Streptococcus and Bacteroides

Oral strains of Fusobacterium nucleatum showed haemagglutination (HA) of sheep red blood cells and attachment of HA-active F. nucleatum fragments to other microorganisms allowed a means of studying microbial surface interactions. HA-active sonicated fragments (SF) prepared from F. nucleatum were mixed with whole cell suspensions of 48 bacterial strains and, after incubation, the whole cells were separated from the non-absorbed fragments by differential centrifugation. Attachment of F. nucleatum fragments to the cells was indicated by a reduction in the HA activity of the SF in the supernatant fluid remaining after absorption with whole cells. HA activity of the microbial cells used for absorption and the detection of F. nucleatum fragments on these cells by an indirect fluorescent antibody technique provided further evidence of attachment. Of the 48 strains tested, 10 absorbed F. nucleatum HA-active fragments. They included Bacteroides gingivalis, Bacteroides fragilis subsp. distasonis, Bacteroides corrodens, Streptococcus morbillorum, Streptococcus sanguis (Blackburn and JC 74) and Streptococcus mutans AHT, BHT, 10449 and 6715. Chelators revealed that F. nucleatum attached to the microorganisms via a Ca2+-dependent interaction. Sugar inhibition demonstrated that F. nucleatum attached to the microorganisms via a D-galactose-containing moiety on their surface. A reduction in the absorption of F. nucleatum HA-active fragments by Strep. mutans grown in a higher concentration of sucrose was observed.

Eikenella corrodens adherence to human buccal epithelial cells

The mechanism of Eikenella corrodens adherence to human buccal epithelial cells in vitro was studied. Initial experiments to determine the optimal conditions for adherence of E. corrodens to buccal epithelial cells showed that adherence was dependent on time, temperature, bacterial concentration, and pH. Different strains of E. corrodens varied in their ability to adhere, and strain 1073 showed the greatest ability in adherence. Strain 1073 was selected for studies of adherence mechanisms. Trypsin treatment or heating (100 degrees C, 10 min) of the bacterial cells abolished their capacity to adhere to buccal epithelial cells. Treatment of buccal epithelial cells with trypsin also abolished adherence of E. corrodens 1073, whereas neuraminidase treatment of buccal epithelial cells enhanced the adherence. The adherence was inhibited by ethylenediaminetetraacetic acid and restored by adding Ca2+. The adherence was remarkably inhibited by sugars containing D-galactose and n-acetyl-D-galactosamine. Treatment of neuraminidase-treated epithelial cells with sodium metaperiodate or alpha- and beta-galactosidase did not decrease the adherence. These data suggest that adherence of E. corrodens 1073 to human buccal epithelial cells may require the interaction of lectin-like proteins on the bacterial surface with galactose-like receptors on the surface of epithelial cells.

Serum antibodies to oral Bacteroides asaccharolyticus (Bacteroides gingivalis): relationship to age and periondontal disease

An enzyme-linked immunosorbent assay microplate method was used for measuring levels of antibody specific for the oral serotype of Bacteroides asaccharolyticus (Bacteroides gingivalis) in serum samples obtained from umbilical cords, infants, children, periodontally normal adults, and edentulous adults. Serum from patients with various periodontal diseases, including adult periodontitis, localized juvenile periodontitis, generalized juvenile periodontitis, post-localized juvenile periodontitis, and acute necrotizing ulcerative gingivitis, were also studied. A positive correlation between increase in age and increase in both prevalence and level of specific antibody in the G, A, and M classes of immunoglobulins was observed. This indicates that antibodies reactive with oral B. asaccharolyticus found in up to 84% of normal adults are natural antibodies, presumably with a protective role. Among the patient groups, those with adult periodontitis were found to have levels of immunoglobulin G antibodies to oral B. asaccharolyticus that were five times higher than the antibody levels found in control subjects. The levels of IgG antibodies to this organism in the other patient groups were comparable to the levels found in the control group. However, 50% of the individuals in the generalized juvenile periodontitis group had high levels of immunoglobulin G antibodies to B. asaccharolyticus, suggesting heterogeneity with respect to immune response in these patients. These results indicate that antibodies to oral B. asaccharolyticus (B. gingivalis) occur at low levels in most normal children and adults and that the rise in titer of the specific antibodies of each major class of immunoglobulins parallels the ontogenic change in serum levels of that isotype. In contrast, there is a marked increase in titer of immunoglobulin G antibodies to oral B. asaccharolyticus in the group of patients with adult periodontitis and in patients with the generalized form of juvenile periodontitis.

Antimicrobial effect of fluorides on Bacteroides melaninogenicus subspecies and Bacteroides asaccharolyticus

This study was undertaken to determine whether the suspected periodontopathogens Bacteroides melaninogenicus ss melaninogenicus and intermedius and Bacteroides asaccharolyticus are killed by clinically used topical fluorides. The viability of each organism was examined after exposure to three fluoride compounds, stannous (SnF2), acidulated phosphate (APF), and neutral sodium (NaF), for 1 and 8 h. Stannous fluoride was found to be effective at lowest fluoride concentrations with APF next in effectiveness. NaF required the highest concentrations of fluoride to kill test organisms. Longer exposure times were found to be more effective at lower concentrations. Data obtained in this study with gram-negative organisms support and extend previous information regarding the antibacterial effect of fluorides against gram-positive periodontopathogens.

Identification of the major adherence ligand of Klebsiella pneumoniae in the receptor for coliphage T7 and alteration of Klebsiella adherence properties by lysogenic conversion

We have studied the adherence of both laboratory and wild-type Klebsiella pneumoniae strains, isolated from sputum, urine, and stool samples, to human buccal and intestinal and urinary tract epithelial cells. Of 32 unencapsulated strains, 30 adhered to all epithelial cells tested. Four K. pneumoniae strains lysogenic for AP3, a phage which causes conversion to resistance of coliphages T3, T7, and phi I, were all unable to adhere to epithelial cells. One of these strains was cured from phage infection and became capable of adhering, Spontaneous mutants resistant to coliphage T7, as well as K. pneumoniae K59-sensitive cells preadsorbed with inactivated T7 particles, did not adhere to epithelial cells. All strains capable of adhering were able to adsorb coliphage T7 and T3, whereas all nonadhesive strains were not. AP3-like prophages were induced from 7 of 12 nonadhesive Klebsiella strains. A laboratory strain which was able to adhere was lysogenized with 2 of these phages. In both cases, the strain lost its ability to adsorb coliphages T3, T7, and phi I and to adhere to human epithelial cells. All K. pneumoniae adhesive strains agglutinated yeast cells, whereas the nonadhesive strains did not. Competition studies have shown that D-mannose and concanavalin A prevented adherence to human epithelial cells, yeast agglutination, and adsorption of coliphage T7 to K. pneumoniae cells. It is concluded that in K. pneumoniae adherence to epithelial cells is mediated by the receptor for coliphages T7 (and T3), which in turn recognizes D-mannose in the receptors it binds.

Attachment of Actinomyces naeslundii to human buccal epithelial cells

A standardized assay was used to measure the attachment of Actinomyces naeslundii ATCC 12104 to washed human buccal epithelial cells. Treatment of the A. naeslundii cells with hyaluronidases, wheat germ lipase, protease, trypsin, heat, or sonic oscillation significantly reduced their ability to attach to epithelial cells. Treatment of the epithelial cells with the above enzymes did not influence the attachment of A. naeslundii. Extraction of A. naeslundii with NaOH also significantly reduced the ability of the bacterium to attach to human buccal epithelial cells. The neutralized and dialyzed NaOH extract contained both carbohydrate and protein substances in a ratio of about 1:1. Adding this extract back to the extracted bacterial cells partially restored their ability to attach to epithelial cells. When the NaOH extract was preincubated with epithelial cells and residual extract was removed by washing, attachment of normal A. naeslundii was partially blocked. The ability of the extracted material to block attachment was significantly reduced when treated with hyaluronidases or with wheat germ lipase. Treatment with heat, protease, or trypsin did not significantly reduce the ability of the extracted materials to block attachment. Pretreatment of the epithelial cells with hyaluronic acid or chondroitin sulfate also reduced subsequent attachment of normal A. naeslundii cells. Pretreatment of epithelial cells with dextrans, proteins, or unpure mannose did not influence subsequent attachment of A. naeslundii. Pretreatment of A. naeslundii with galactose and lactose significantly inhibited attachment to normal epithelial cells. The results suggest that the attachment of A. naeslundii to human buccal epithelial cells may involve mucopolysaccharides similar to hyaluronic acid on the surface of the bacterial cells. Other attachment mechanisms may also be operative.

Characterization of the adherence properties of Streptococcus salivarius

The adherence and aggregation properties of 46 human oral Streptococcus salivarius isolates were examined. A total of 41% of the isolates aggregated with whole human saliva, 50% aggregated with human erythrocytes, and 85% adhered to human buccal epithelial cells. Strains that aggregated with saliva and erythrocytes usually reacted with Streptococcus group K typing serum whereas the non-hemagglutinating strains did not. K+ strains also adhered more strongly to human buccal epithelial cells than K- strains. All isolates coaggregated with Fusobacterium nucleatum LF and Bacteroides asaccharolyticus 2D, 91% coaggregated with Veillonella alcalescens V1, and 50% coaggregated with Veillonella parvula V4. S. salivarius HB aggregated with saliva from 15 different human donors and aggregated with human erythrocytes irrespective of the blood group. This strain only weakly aggregated with rat saliva or rat erythrocytes. We isolated mutants which concomitantly lost the ability to agglutinate erythrocytes, aggregate with saliva, and bind to buccal epithelial cells, but retained their interbacterial aggregation properties. A second class of mutants lost the ability to coaggregate with Veillonella, but these mutants retained all of the other aggregation properties. Treatment of S. salivarius HB cells with pronase or subtilisin destroyed their ability to aggregate with saliva and erythrocytes and to bind to buccal epithelial cells. The unique characteristics of the aggregation and adherence reactions were suggested by differences in the rate of loss of activity during protease treatment and in the response to chemical modification. The presence of saliva did not affect hemagglutination and adherence to buccal epithelial cells. Binding of the salivary aggregating factor to the bacteria could be distinguished from aggregation on the basis that the latter required divalent cations. The factor involved in coaggregation with F. nucleatum LF was physicochemically different from the other factors, since it was resistant to heat and to extraction with trichloroacetic acid, aqueous phenol, sodium dodecyl sulfate, and formamide, but was sensitive to proteases and was present in both classes of mutants. Coaggregation with V. alcalescens was not sensitive to proteases. A variety of mono- and disaccharides had no influence on any of the reactions tested.

Attachment of oral Cytophaga species to hydroxyapatite-containing surfaces

Model systems simulating the cementum portion of teeth were used to characterize the attachment process by which certain species of oral Cytophaga initiate the colonization of the tooth root surface in vitro. The adsorption of these bacteria to spheroidal hydroxyapatite beads and mechanically powdered root material followed Langmuir isotherm kinetics. From such data, the number of binding sites per 20 mg of substrate and the affinity constants were evaluated for two strains of Cytophaga sp. Resting cells of the two strains tested adhered relatively tenaciously to hydroxyapatite beads in numbers similar to those observed with cells of Streptococcus sanguis. Attachment of bacteria to the substrates was partially inhibited by (i) coating the substrates with human serum or saliva, (ii) pretreating cell suspensions with proteinase K or phospholipase C or D, or (iii) exposing the cells to temperatures greater than 60 degrees C for 15 min. Treating resting cell suspensions with pronase, neuraminidase, phospholipase A2, or 0.1 M ethylenediaminetetraacetic acid had no effect on the attachment process.

Antigenic studies of oral and nonoral black-pigmented Bacteroides strains

Antigens of several oral and nonoral strains of Bacteroides asaccharolyticus (proposed classification of oral B. asaccharolyticus, Bacteroides gingivalis), Bacteroides melaninogenicus subsp. intermedius, B. melaninogenicus subsp. melaninogenicus, and B. melaninogenicus subsp. levii were identified in soluble preparations obtained by sonication, autoclaving, and NaOH treatment of whole bacterial cells. The sonicate preparations contained the most complete representation of soluble antigens using antisera to the whole organism in gel precipitation tests. Among strains of B. melaninogenicus subsp. intermedius many common antigens were detected, and no consistent antigenic differences were seen between strains from oral and nonoral sites. None of the antigens of B. melaninogenicus subsp. intermedius reacted with sera raised to several strains of oral or nonoral B. asaccharolyticus, nor did antigens prepared from the latter strains react with antisera to B. melaninogenicus subsp. intermedius. At least one common antigen was shared by strains of B. melaninogenicus subsp. intermedius and strains of B. melaninogenicus subsp. melaninogenicus; however, subspecies-specific antigens were also found. Antigens from and antisera to oral and nonoral strains of B. asaccharolyticus did not react with sera to and antigens from B. melaninogenicus subsp. melaninogenicus. Strains of B. asaccharolyticus isolated from the oral cavity were antigenically distinct from strains of B. asaccharolyticus obtained from nonoral sites and lesions. This lack of cross-reactivity between the oral and nonoral strains of B. asaccharolyticus together with recent findings of marked genetic differences between oral and nonoral strains of B. asaccharolyticus suggest that these groups of organisms may represent different species.

Attachment of bacteria to mammalian surfaces

Much attention has been devoted to the study of bacterial adherence to mammalian surfaces in vitro during the past several years. Some in vivo evidence also suggests that this process may indeed be an integral part of the pathogenesis of colonization and certain infections. The biochemical basis of attachment and definition of the actual receptor sites involved are just starting to become known and seem to be different amongst individual bacteria genera. However, pili may mediate attachment of a variety of gram-negative organisms to receptor cells, and streptococcal lipoteichoic acids probably serve a similar function. Some recent study methods and results in this field are reviewed.

Periodontal therapy in humans. I. Microbiological and clinical effects of a single course of periodontal scaling and root planing, and of adjunctive tetracycline therapy

The present results showed that maarked and long-lasting changes in the subgingival microflora associated with periodontal disease could be achieved by a single course of periodontal treatment. Immediately following therapy, the total number of subgingival organisms decreased 10- to 100-fold and the proportions of cultivable Gram negative organisms and anaerobic organisms generally decreased 3- to 4-fold or more. After treatment, most periodontal pockets were populated by a scant microflora predominated by facultative Actinomyces and Streptococcus species. The kinetics of the subgingival bacterial recolonization revealed that the total cell counts and the proportions of spirochetes and Capnocytophaga species did not reach their pretreatment levels even after 6 months. Other Gram negative anaerobic species returned to pretreatment proportions after 3 to 6 months. Several Gram positive species exhibited higher posttreatment than pretreatment proportions throughout the 6 months study. The microbiological shifts paralleled significant changes in the clinical status of the periodontal tissues. Following therapy, the periodontal pocket depths decreased generally 1 to 4 mm, the gingival inflammatory index, the gingival fluid flow, and the suppurative index were generally lower, and nine of 33 test pockets examined showed apposition of alveolar bone. The microbiological and clinical changes described were exhibited by two patients treated with periodontal scaling and root planing alone and by two patients treated with the adjunctive use of systemic tetracycline therapy. In two other patients, mechanical periodontal therapy only slightly reduced the total number of subgingival organisms and the proportions of spirochetes and other Gram negative anaerobic rods. A shift in the subgingival microbial composition was achieved in these two patients after tetracycline therapy. The following model for treatment of periodontal disease is proposed: (1) Conventional therapy including thorough periodontal scaling and root planing; (2) Monitoring the subgingival flora and the clinical course; and (3) Use of antimicrobial therapy in refractory cases. Further studies are needed to develop means for rapid identification of refractory patients, and to determine the optimal antimicrobial agent, the optimal route of administration, and the optimal dosage regime.

Direct hemagglutination technique for differentiating Bacteroides asaccharolyticus oral strains from nonoral strains

A simple and economical method for differentiating Bacteroides asaccharolyticus of oral sources from nonoral sources is described. The present data indicate that oral strains of B. asaccharolyticus strongly agglutinate sheep erythrocytes, whereas isolates from various nonoral sites typically are devoid of hemagglutination activity. The direct hemagglutination test may aid in determining the source of B. asaccharolyticus present in an infection, and thus the procedure has potential value as a means of biotyping.

In vitro studies of dental plaque formation: adsorption of oral streptococci to hydroxyaptite

A mixture of saliva-coated hydroxyapatite beads and radioactively labeled bacteria has been employed as an in vitro model for the initial phase of dental plaque formation. Adsorption in this model can be expressed by the Langmuir adsorption isotherm, and the adherence of oral streptococci can be expressed as the product of the affinity constant (Ka) and the number of binding sites (N), KaN. With this approach, Streptococcus sanguis serotype 1 strains adhered better (KaN = [187 +/- 72] X 10(-2)) than serotype 2 strains (KaN = [97 +/- 84] X 10(-2)); a t test showed this difference to be statistically significant to the 99.99% confidence level. Strains of S. mitis, S. mutans, and S. salivarius did not appear to adhere as well. To analyze the bacterial receptors involved in adherence, competition studies in which increasing quantities of unlabeled bacteria were added to a fixed quantity (4 X 10(9) cells per ml) of 3H-labeled serotype 1, reference strain S. sanguis G9B, were performed. These studies indicated that the type 1 strains competed for the same, or closely related, binding sites. Competition studies using serotype 2 S. sanguis strains resulted in an increased binding of reference strain G9B to hydroxyapatite. Scanning electron microscopy indicated this effect was due to the formation of localized aggregations of bacteria, presumably representing the two bacterial types. The results of competition studies with S. mitis were variable, and several strains of other oral bacteria showed little or no competition.

Effect of mechanical plaque control on development of subgingival plaque and initial gingivitis in neutropenic dogs

Histologic, histometric and morphometric investigations were performed on the gingival tissues of three neutropenic dogs. Over a period of 4 d the animals had been subjected to daily toothcleaning of the left side of both jaws, whereas plaque accumulation and subsequent gingivitis occurred on the uncleaned teeth of the right side of both jaws. Observations and data revealed that subgingival plaque had formed in both sides and extended further apically (max. 0.6 mm) on the cleaned than on the uncleaned sides. In the responding gingival tissues, leukocytes of the junctional epithelium were more numerous and blood vessels of the marginal connective tissue occupied a greater volume on the cleaned sides when compared with the uncleaned sides. It is concluded that neutrophilic granulocytes normally help to prevent bacterial invasion into the dentogingival region, and that, in the presence of subgingival plaque, toothcleaning may aggravate the inflammatory response of the gingiva.

Longitudinal study of experimentally induced periodontal disease in Macaca arctoides: relationship between microflora and alveolar bone loss

Macaca arctoides monkeys develop periodontal disease, and they harbor a periodontopathic indigenous flora largely similar to that of humans. This study showed that various Haemophilus isolates and H2O2-splitting asaccharolytic Bacteroides melaninogenicus strains constituted major segments of the monkey periodontal microflora. These organisms have not been previously identified among human isolates. Furthermore, the present data revealed that asaccharolytic B. melaninogenicus strains increased in proportion from a few percent to about 66% of the total isolates concomitant with the development of a significant loss of alveolar bone mass. Hence, this study strongly implicates B. melaninogenicus subsp. asaccharolyticus and closely related strains as important pathogens in actively destructive periodontal disease.