Antigenic characteristics and serological identification of 10 black-pigmented Bacteroides species

Strains of 10 black-pigmented Bacteroides species were serologically characterized using absorbed and unabsorbed rabbit antisera. An agglutination test using intact cells or heated cells (100 degrees C for 60 min) from each species and unabsorbed antisera revealed only homologous reactions with little or no reactivity in heterologous assays. Immunodiffusion tests using sonicated antigen demonstrated that Bacteroides gingivalis, B. endodontalis, B. asaccharolyticus, B. macacae, and B. levii are antigenically distinct. Strains of B. gingivalis, B. endodontalis, and B. asaccharolyticus were also clearly identified by the indirect immunofluorescent antibody method. B. intermedius, B. corporis, B. loescheii, B. melaninogenicus, and B. denticola possessed common antigens; however, species-specific antigens detectable with immunoabsorbed antisera were also demonstrated. B. intermedius strains isolated from the human oral cavity included at least two serogroups. In each black-pigmented Bacteroides species, lipopolysaccharide constituted one of the species-specific antigens.

The condition of the soft tissues at tooth and fixture abutments supporting fixed bridges. A microbiological and histological study

In 10 partially edentulous patients provided with fixed bridgework supported by the combination of tooth and titanium fixture abutments, the condition of the soft tissues surrounding the abutments was examined. Sampling of supra- and subgingival plaque was performed from both teeth and fixtures. The samples were analyzed regarding the total bacterial counts, the relative distribution of bacterial morphotypes and the cultivable microflora. From each patient, soft tissue biopsies were obtained from 1 tooth and 1 fixture abutment, and the specimens were analyzed for the presence and extension of inflammatory cell infiltrates. The microbiological examination showed that the distribution of bacterial morphotypes in the supra- and subgingival plaque both at teeth and fixtures were similar, irrespective of localization and type of abutment. Nonmotile rods dominated the microflora, whereas spirochetes were either not detected or occurred in very low proportions. From the histological analysis, it was found that a majority of the soft tissue biopsies (75-80%) from both tooth and fixture sites contained only very small inflammatory cell infiltrates.

Selective medium for the isolation of Haemophilus aphrophilus from the human periodontium and other oral sites and the low proportion of the organism in the oral flora

We developed a medium for the selective recovery of Haemophilus aphrophilus. The medium, designated TSBVF, was composed of 4% tryptic soy agar, 10% heat-inactivated horse serum, 75 micrograms of bacitracin per ml, 5 micrograms of vancomycin per ml, and 50 micrograms of sodium fluoride per ml. TSBVF yielded a threefold higher recovery of oral H. aphrophilus than did chocolate agar with 75 micrograms of bacitracin per ml, which is a medium routinely used to diagnose human Haemophilus infections. H. aphrophilus and the few contaminating organisms on TSBVF were readily distinguished on the basis of colony morphology. The H. aphrophilus isolates exhibited variable fermentation of raffinose and dextrin but otherwise were biochemically similar. In a clinical study, H. aphrophilus was frequently recovered from supragingival plaque and saliva and occasionally from buccal mucosa and the tonsils. It was also isolated from 29 of 56 subgingival sites in 11 of 14 subjects. Its proportion of the subgingival microflora averaged 0.13% for healthy periodontal sites, 0.05% for adult periodontitis lesions, and 0.03% for localized juvenile periodontitis lesions. We concluded that H. aphrophilus is an indigenous bacterium of the human oral cavity. It occurs in low proportions in subgingival plaque and plays no apparent role in advanced periodontal disease in humans.

Antibiotic susceptibility of anaerobic bacteria from the human oral cavity

Anaerobic, agar-dilution, minimal inhibitory concentrations (MICs) of 18 antibiotics are given for the numerically important bacterial groups from the human oral cavity. Strains are divided into susceptibility categories using the guidelines for interpretation of MICs suggested by the National Committee for Clinical Laboratory Standards. These guidelines are based on data on antibiotic concentrations attainable in serum following various dosage regimens. MICs are also compared with attainable gingival fluid levels where these are known. The highest percentages of strains were susceptible to tetracycline, with 89% of the 139 strains tested susceptible to serum levels and 97% conditionally susceptible to attainable gingival fluid levels. Ninety-eight percent of strains were conditionally susceptible to attainable gingival fluid levels of minocycline, but many strains, including Actinobacillus actinomycetemcomitans, were only moderately susceptible to attainable serum levels of this tetracycline analogue. Carbenicillin was effective against most groups of organisms, with the important exception of A. actinomycetemcomitans, at serum levels attainable with oral formulations of carbenicillin. Only 2% of the total strains tested were resistant to penicillin, while 33% of strains were categorized as moderately susceptible. Clindamycin was active against many strains of Gram-negative bacteria but was not active against A. actinomycetemcomitans, some Bacteroides, Eikenella corrodens, or the anaerobic vibrios. Metronidazole was active against A. actinomycetemcomitans, all five groups of oral Bacteroides tested, and against Capnocytophaga species. Chloramphenicol was active against A. actinomycetemcomitans, but not against most of the other groups of oral organisms. Nearly all groups contained strains non-susceptible to serum levels attainable with the usual doses of erythromycin, spiramycin, vancomycin, kanamycin, neomycin, streptomycin, doxycycline, oxytetracycline, or chlortetracycline; several strains were resistant to maximum attainable serum levels of each of these antibiotics except doxycycline.

Relationship between some subgingival bacteria and periodontal pocket depth and gain or loss of periodontal attachment after treatment of adult periodontitis

We studied the association between post-treatment periodontal disease activity and subgingival Bacteroides gingivalis, Bacteroides intermedius, spirochetes and motile rods. 20 adults, 22-62 years, with moderate-to-severe periodontitis participated in a split-mouth treatment study. All individual quadrants received supragingival cleaning and in addition, subgingival scaling and a NaHCO3-NaCl-H2O2 slurry, subgingival scaling alone, slurry alone, or no subgingival treatment. Post-treatment periodontal disease status was determined over a period of 12 months by changes in probing periodontal pocket depth and probing periodontal attachment level. Subgingival specimens obtained by paper point-sampling were evaluated for B. gingivalis and B. intermedius using indirect immunofluorescence and for spirochetes and motile rods using bright light phase contrast microscopy. A total of 142 periodontitis lesions representing all 4 quadrants of the 20 subjects were studied. The relationship between clinical data and bacteria was analyzed using logistic regression. The probability of the study organisms being present in subgingival sites at 3 to 6 months after treatment increased with increased residual pocket depth. The presence of B. gingivalis showed a strong positive association (p less than 0.004) with loss of periodontal attachment. A significant association was also found for spirochetes (p less than 0.008) but not for motile rods (p greater than 0.35) or B. intermedius (p greater than 0.13). Similar results were obtained at 12 months after therapy, except that the presence of motile rods was significantly associated with loss of periodontal attachment (p less than 0.03). Caution must be exercised when using B. gingivalis or spirochetes to evaluate treatment efficacy. If the presence of these organisms was utilized to indicate progressing periodontitis, many active lesions could be identified, and only 1 to 17% and 13 to 43% of sites in remission at 3-6 months after therapy would be expected to harbor B. gingivalis and spirochetes, respectively. The consequences of treating periodontal sites in remission would mainly be limited to cost and inconvenience. However, since several active periodontitis lesions did not reveal the organisms, treatment decisions based solely on the absence of the organisms may result in the omission of needed therapy. As a practical consideration, periodontal treatment should be continued as long as B. gingivalis and maybe spirochetes are detectable in the subgingival microflora. In the absence of these organisms, and until additional periodontal pathogens have become known, the decision to continue or conclude periodontal therapy must b

Microbiological and clinical effects of surgical treatment of localized juvenile periodontitis

Since Actinobacillus actinomycetemcomitans appears to be a key etiologic agent in localized juvenile periodontitis, this study determined the effectiveness of different treatment modalities in suppressing A. actinomycetemcomitans in localized juvenile periodontitis lesions. A total of 25 deep periodontal lesions from 7 patients with localized juvenile periodontitis were included in the study. The test periodontal lesions either received scaling and root planing alone, scaling and root planing together with soft tissue curettage, or modified Widman flap surgery. Subgingival A. actinomycetemcomitans were enumerated using selective culturing. Clinical measurements included changes in probing periodontal attachment level, probing periodontal pocket depth, gingival index, plaque index, and digital subtraction of standardized serial radiographs. The microbiological and clinical effects of treatment were monitored over a period of 16 weeks. All periodontal lesions studied demonstrated high numbers of A. actinomycetemcomitans prior to treatment. Scaling and root planing alone did not markedly change the subgingival A. actinomycetemcomitans counts, nor any of the clinical parameters studied. In contrast, soft tissue curettage as well as modified Widman flap surgery suppressed A. actinomycetemcomitans to undetectable levels immediately after therapy in more than 80% of the lesions studied. A total of 5 periodontal lesions exhibited gain of probing periodontal attachment after subgingival curettage or Widman flap treatment; 3 of these sites revealed no detectable A. actinomycetemcomitans, and the remaining 2 sites harbored only low levels of A. actinomycetemcomitans. 5 periodontal lesions which lost probing attachment after treatment all demonstrated high numbers of subgingival A. actinomycetemcomitans. Changes in alveolar bone, assessed by digital subtraction of serial radiographs, correlated with changes in probing periodontal attachment level, confirming the clinical results. The present study revealed a close relationship between post-treatment A. actinomycetemcomitans levels and the clinical response to treatment, which supports the concept that A. actinomycetemcomitans is an important organism in the etiology of localized juvenile periodontitis. This study also showed that a substantial suppression of subgingival A. actinomycetemcomitans cannot be achieved by periodontal scaling and root planing alone, but can be accomplished by surgical removal of periodontal tissues.(ABSTRACT TRUNCATED AT 400 WORDS)

Subgingival microorganisms and bacterial virulence factors in periodontitis

Considerable information has come forth in recent years on the pathogenic organisms in human periodontitis and the sequence of events by which they produce periodontal disease. Important periodontopathogens include Bacteroides gingivalis, Bacteroides intermedius and Actinobacillus actinomycetemcomitans. Virulence factors of B. gingivalis and B. intermedius may mainly involve enzymes with potential to interfere with host defenses and to disintegrate periodontal tissues. Pathogenic properties of A. actinomycetemcomitans appear predominantly to be exerted by leukotoxin and other noxious products.

Susceptibility of human oral anaerobic bacteria to antibiotics suitable for topical use

17 antibiotics, with potential for topical use, were tested for their activity against the human oral flora. Concentrations (mumol/l) required to inhibit 90% of test strains are presented and drug activities are compared. The total cultivable oral flora was susceptible to the tetracyclines including tetracycline itself, minocycline, doxycycline, and oxytetracycline and to erythromycin. On the other hand, actinobolin, kanamycin, neomycin, streptomycin, spiramycin, tyrothricin, vancomycin, clindamycin, and chloramphenicol were ineffective against many of the human oral anaerobic bacteria even at high concentration. Penicillin was effective at high concentrations but could not be recommended because organisms which are not inhibited by low concentrations are penicillinase producers. Carbenicillin was effective against all organisms except Actinobacillus actinomycetemcomitans. The gram-negative organisms involved in adult periodontitis were most susceptible to the tetracyclines, tyrothricin, carbenicillin and clindamycin, while those associated with localized juvenile periodontitis were susceptible to the tetracyclines or erythromycin. These data, combined with the previous findings that some tetracyclines exhibit marked substantivity and collagenase inhibition activity, indicate that tetracycline or minocycline are likely to be good choices in the treatment or prevention of oral diseases.

Transmission and colonization of Actinobacillus actinomycetemcomitans in localized juvenile periodontitis patients

Actinobacillus actinomycetemcomitans is a Gram-negative oral microorganism, which has been implicated in the etiology of localized juvenile periodontitis and in severe medical infections such as bacterial endocarditis. This study evaluated the ability of periodontal probes to transmit A actinomycetemcomitans from juvenile periodontitis lesions to healthy gingival sulci in the same patient. Localized juvenile periodontitis patients exhibiting first molar and incisor alveolar bone loss and with large numbers of A actinomycetemcomitans in deep periodontal pockets were included in this study. A periodontal probe was inserted into periodontal pockets of 6 mm or greater depth. The probe was then placed into a healthy gingival sulcus of 3 mm or less, in the same subject. Fifty-five transfers by probing were made and A actinomycetemcomitans in both the donor and recipient sites was assessed by a selective culture technique. The results indicate that periodontal probes can become contaminated with A actinomycetemcomitans from juvenile periodontitis lesions during routine dental examinations and can transfer this microorganism from infected to previously uninfected sites. However, A actinomycetemcomitans inoculated into the healthy gingival sulci did not permanently colonize these sites since the organisms were eliminated within 3 weeks.

In situ identification of bacterial species in marine microfouling films by using an immunofluorescence technique

An immunofluorescence technique was developed for the in situ identification of specific bacteria in marine microfouling films. Microorganisms adherent to glass plates after 30 days of immersion in a synthetic seawater system were cultured and classified by biochemical tests, flagellar arrangement, and the API 20E system. All isolates were gram-negative aerobic or facultative motile rods, predominantly Pseudomonas spp. Rabbit antisera to the five dominant organisms including Achromobacter spp., Comamonas terrigena, P. putrefaciens, a yellow-pigmented Pseudomonas sp., and Vibrio alginolyticus were prepared. These antisera were shown to be species specific in indirect immunofluorescence assays against a battery of 26 marine isolates from 14 bacterial species, with the exception of antisera to the Pseudomonas spp, which cross-reacted with each other but not with test bacteria of other genera. These immunofluorescent reagents enabled the in situ identification of all five bacterial species in microfouling films. Low-surface-energy test plates had smaller numbers of adherent bacteria in microfouling films than medium-surface-energy test plates, suggesting that the degree of microfouling may be influenced by the surface energy. In addition, the reagents could identify up to 39% of the attached bacteria in microfouling films spontaneously formed on steel plates in flow cells deployed in different areas of the Atlantic Ocean. The microbial composition of the ocean-formed films varied with the geographical area of their formation. The present results indicate that immunofluorescence techniques may provide a rapid and reliable means to identify, in situ, specific bacteria in marine microfouling films.

Purification and characterization of the serotype c antigen from Actinobacillus actinomycetemcomitans

The serotype c antigen from Actinobacillus actinomycetemcomitans was purified with fractional ethanol precipitation of cell-free culture supernatant, sequential ion-exchange chromatography, and gel filtration chromatography. The preparation obtained demonstrated a single precipitin line in immunodiffusion, immunoelectrophoresis, and crossed immunoelectrophoresis when rabbit antisera to serotype c whole bacterial cells were used. No immunological reaction was detected with antisera to serotype c lipopolysaccharide, indicating that lipopolysaccharide was not present in the preparation. The serotype c antigen was composed of 95% carbohydrate, 2% protein, and 3.1% phosphate. Gas chromatographic analysis of the antigen obtained from growth in either complex or chemically defined media revealed that the carbohydrate constituent was composed of 84 to 90.1% mannose, 4.8 to 16% glucose, 1.9% N-acetylglucosamine, 1.4% fucose, and 0.2% galactose. The present data suggest that A. actinomycetemcomitans serotype c antigen is predominantly a mannose-containing carbohydrate suggestive of a mannan.

Host responses in periodontal diseases

Great progress has been made in our understanding of the pathogenesis of periodontal disease, the primary role of bacteria as etiologic agents, and the critical modifying role of host responses. It is useful to consider several stages in the pathogenesis of periodontal disease - (a) colonization, (b) invasion, (c) destruction, and (d) healing - and to place into perspective the various host responses as they may affect each of these four stages (Table 5). With respect to colonization, although very little direct evidence is available, it is reasonable to suggest that antibodies, either secretory or serum-derived, acting by virtue of their ability to block attachment, could inhibit colonization by immune reduction of adherence mechanisms. With respect to invasion of the tissue, it appears that phagocytes, particularly the neutrophils, are important, acting in concert with opsonic antibody and complement in ingesting and killing the periodontal microflora before or during the early invasive process. A major advance in our understanding of the pathogenesis of periodontal diseases is the realization that the virulence of periodontopathic bacteria relates to their leukaggressive properties, allowing them to evade neutrophil protective mechanisms. Invasion of the periodontal tissues by bacterial products may be inhibited by the complexing of these products with antibody with the formation of antigen-antibody complexes that are phagocytosed and digested, particularly by scavenger phagocytes such as the macrophage. With respect to the destructive phase of periodontal disease, it is clear that the direct effect of lymphocytes mediated either through direct cytotoxic activity, or through biologically-active destructive lymphokines (such as alpha-lymphotoxin and osteoclast activating factor), can lead to tissue destruction. Macrophages, through the production of monokines, collagenase, and reactive oxygen species, can also lead to tissue destruction. The direct effects of bacterial toxins or enzymes which can lead to tissue destruction can be inhibited by complexing with antitoxic or enzyme-neutralizing antibodies. With respect to healing and fibrosis, very little direct information is available; however, it is possible that the lymphocytes and macrophages affect fibrosis by the production of chemotactic factors for fibroblasts which would be expected to bring them to the area of periodontal inflammation and also by production of fibroblast-activating factors, which then cause the fibroblasts to proliferate and produce collagen which replaces lost collagen or results in fibrosis.(ABSTRACT TRUNCATED AT 400 WORDS)

Microbiological study of localized juvenile periodontitis in Panama

The occurrence of subgingival Actinobacillus actinomycetemcomitans and Capnocytophaga in 12 localized juvenile periodontitis and 10 gingivitis patients from Panama was determined using selective culture techniques. A actinomycetemcomitans was present in all localized juvenile periodontitis lesions studied and was, on average, recovered in hundred-fold-higher numbers from localized juvenile periodontitis lesions than from gingivitis lesions. Capnocytophaga was only recovered in approximately threefold-higher numbers from localized juvenile periodontitis than from gingivitis. The study confirms and extends previous data indicating a close relationship between A actinomycetemcomitans and localized juvenile periodontitis. It is proposed that identification of A actinomycetemcomitans may be a valuable adjunct in the diagnosis of localized juvenile periodontitis.

Cellular fatty acid and soluble protein profiles of oral fusobacteria

We compared the cellular fatty acid and protein content of 43 strains of oral fusobacteria isolated from patients with chronic gingivitis, acute necrotizing ulcerative gingivitis, and juvenile and adult periodontitis, as well as from the stump-tailed macaque, to that of eight reference strains of oral and non-oral Fusobacterium species. A gas-liquid chromatographic examination of trimethylsilyl derivatives of the fatty acid methyl esters revealed n14:0, 3-OH-14:0, n16:0, 16:1, 3-OH-16:0, n18:0, and 18:1 in each of the 51 study strains, and a variable occurrence of 14 other fatty acids. The n16:0 to 3-OH-16:0 ratio distinguished between Fusobacterium nucleatum and the non-oral species Fusobacterium varium, Fusobacterium necrophorum, Fusobacterium russii, Fusobacterium necrogenes, Fusobacterium mortiferum, and Fusobacterium naviforme. The soluble protein content, as determined by polyacrylamide gel electrophoresis, varied considerably among the oral fusobacterial strains studied, and underscored the heterogenous nature of these organisms. "Fingerprinting" of oral fusobacteria may be readily accomplished by polypeptide analysis.

Actinobacillus actinomycetemcomitans in human periodontal disease. Prevalence in patient groups and distribution of biotypes and serotypes within families

Actinobacillus actinomycetemcomitans is a Gram-negative oral bacterium which has been implicated in the etiology of localized juvenile periodontitis. In this study, 403 subjects from four study groups were examined for A actinomycetemcomitans in subgingival dental plaque. Samples pooled from at least six periodontal sites were included from each subject. A actinomycetemcomitans was detected in 28 of 29 localized juvenile periodontitis patients but in only 15% of the other subjects including 28 of 134 adult periodontitis patients, 24 of 142 periodontally healthy subjects and 5 of 98 insulin dependent juvenile diabetics with varying degrees of gingivitis. A actinomycetemcomitans isolates from members of five families with localized juvenile periodontitis patients were biotyped on the basis of variable fermentation of dextrin, maltose, mannitol and xylose and serotyped by indirect immunofluorescence using serotype specific rabbit antisera. Individuals within a family all harbored A actinomycetemcomitans of the same biotype and serotype. However, even in families with individuals heavily infected with A actinomycetemcomitans, some family members did not appear to be infected with the organism. The apparent poor transmissibility of A actinomycetemcomitans between individuals may, in part, explain the overall low prevalence of localized juvenile periodontitis and the familial pattern of the disease. The high prevalence of A actinomycetemcomitans in the subgingival plaque of localized juvenile periodontitis patients, compared to the much lower prevalence in other patient groups, supports the hypothesis that A actinomycetemcomitans is an etiologic agent in this periodontal disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Microbiological and clinical effects of topical subgingival antimicrobial treatment on human periodontal disease

This study was undertaken to evaluate the microbiological and clinical effects of a subgingivally applied mixture of H2O2-NaCl and NaHCO3 followed by subgingival irrigation with 1% Betadine in the treatment of periodontal disease. 20 adults with moderate to severe periodontal disease were included in a split mouth design study. All patients were given oral hygiene instruction and were subjected to supragingival scaling in all 4 quadrants, and subgingival scaling and root planing of half the dentition. 10 patients were instructed to use the chemical antimicrobial mixture twice a day instead of dentifrice, and also received professional application of the mixture once every 14 days for 3 months in connection with reinstruction in oral hygiene procedures. The remaining 10 patients received oral hygiene instructions combined with professional tooth cleaning without use of chemicals once every 14 days during a 3-month period. The effect of treatment was evaluated by monitoring the subgingival microflora, clinical periodontal parameters, and by computer assisted subtraction analysis of serial standardized radiographs to determine changes in mass of the supporting alveolar bone. The present study revealed that subgingival debridement combined with mechanical plaque control resulted in decreased numbers of subgingival microorganisms including spirochetes and motile rods, and arrested the progressive breakdown of the periodontal tissues. Topical antimicrobial agents used in combination with subgingival scaling further reduced the subgingival microflora and substantially improved early periodontal healing including gain of probing attachment level and gain in radiographic alveolar bone mass during the 12 months of observation. No clinical improvement but a tendency to further periodontal breakdown was found in the unscaled quadrants, even in those which were subjected to a personal application of the topical antimicrobial mixture. This study indicates that professional and personal subgingival application of a mixture of H2O2-NaCl and NaHCo3 will significantly enhance the microbiological and clinical effects of periodontal scaling and root planing. These agents, and the topical mode of antimicrobial therapy seem promising in the management of human periodontal diseases.

Fusobacterium periodonticum, a new species from the human oral cavity

Isolates of Fusobacterium that differ from type strains of various fusobacterial species with respect to DNA sequence, cellular fatty acid composition, and biochemical activity, were obtained from periodontitis lesions in a patient with insulin-dependent diabetes mellitus. These isolates have the following distinguishing characteristics: 28% guanine + cytosine content; 40% or less DNA homology with type strains of representative fusobacterial species; cell size, 0.5 - 1 X 4 -100 microns; absence of motility; ability to ferment glucose, fructose, and galactose, but not 25 other carbohydrates; ability to produce indole; ability to hydrolyze hippurate but not esculin; sensitivity to bile; ability to produce little or no gas; ability to utilize threonine but not lactate. We propose that the organisms be classified as a distinct species of Fusobacterium to be named Fusobacterium periodonticum. The type strain of this new species has been deposited with the American Type Culture Collection under the designation ATCC 33693.

Suppression of the periodontopathic microflora in localized juvenile periodontitis by systemic tetracycline

Since recent studies have implicated Actinobacillus actinomycetemcomitans in the etiology of localized juvenile periodontitis, this investigation determined the effectiveness of subgingival debridement, topical Betadine Solution, and systemic tetracycline in suppressing subgingival A. actinomycetemcomitans and other microorganisms. A total of 20 deep periodontal pockets and 10 normal periodontal sites of 6 localized juvenile periodontitis patients was included in the study. Each patient was treated in 3 stages over a period of 22 weeks, and the result of treatment was monitored for an additional 38 weeks. The first stage of treatment included plaque control, as well as thorough scaling and root planing, composed of at least 6 h of debridement. No concomitant periodontal surgery was performed. In the second stage, Betadine saturated cotton gauze was inserted into the periodontal pockets for 10 min. Stage 3 involved systemic tetracycline therapy (1 g/day) for 14 days. The subgingival microflora was determined at frequent intervals by selective culturing of A. actinomycetemcomitans and Capnocytophaga and by direct microscopic examination. The clinical effect was assessed by measuring changes in probing periodontal attachment level, probing periodontal pocket depth, radiographic alveolar bone mass, and other relevant clinical parameters. Scaling and root planing reduced the total subgingival bacterial counts and the proportions of certain Gram-negative bacteria, but no periodontal pocket became free of A. actinomycetemcomitans. Betadine application had little or no effect on the subgingival microflora. In contrast, tetracycline administered via the systemic route suppressed A. actinomycetemcomitans, Capnocytophaga, and spirochetes to low or undetectable levels in all test periodontal pockets. A. actinomycetemcomitans reappeared in 9 of the deep periodontal pockets after the administration of tetracycline. Most of these 9 pockets became free of detectable A. actinomycetemcomitans during the second week of tetracycline administration, whereas pockets which yielded no A. actinomycetemcomitans after tetracycline therapy became free of the organisms during the first week of tetracycline treatment. This data suggests that systemic tetracycline therapy of localized juvenile periodontitis should, as a practical rule, be continued for 3 weeks. Periodontal destruction continued in 4 deep pockets which all showed high posttetracycline A. actinomycetemcomitans counts. All 6 pockets which demonstrated a marked gain in periodontal attachment yielded no cultivable A. actinomycetemcomitans. No association was found between periodontal disease status and subgingival Capnocytophaga, spirochetes or motile rods. The present study indicates that A. actinomycetemcomitans is an important etiologic agent in localized juvenile periodontitis.(ABSTRACT TRUNCATED AT 400 WORDS)