In vitro antimicrobial susceptibility of Actinobacillus actinomycetemcomitans

The agar dilution technique was used for determination of the antibiotic susceptibilities of 57 oral isolates and 2 nonoral isolates of Actinobacillus actinomycetemcomitans. Tetracycline, minocycline, and chloramphenicol inhibited more than 96% of the strains tested at a concentration of less than or equal to 2 micrograms/ml; 89% of the strains were inhibited by 2 micrograms of carbenicillin per ml. The other antimicrobial agents tested were less active. Approximately 10% of the A. actinomycetemcomitans strains were resistant to ampicillin, erythromycin, and penicillin G at concentrations of 32 to 64 micrograms/ml. These data suggest that tetracycline and minocycline may be valuable drugs in the treatment of A. actinomycetemcomitans infections.

Evaluation of Fluoretec-M for detection of oral strains of Bacteroides asaccharolyticus and Bacteroides melaninogenicus

Fluoretec-M is a polyvalent conjugate used in direct fluorescent-antibody staining for identification of the Bacteroides asaccharolyticus-Bacteroides melaninogenicus group. The Fluoretec-M reagent detected all oral and nonoral test strains of B. melaninogaenicus subsp. intermedius, all test strains of B. melaninogenicus subsp. melaninogenicus, and the nonoral strains of B. asaccharolyticus. However, the Fluoretec-M polyvalent reagent and the monovalent conjugates which constitute Fluoretec-M did not detect the oral strains B. asaccharolyticus. The use of Fluoretec-M can therefore generate false-negative results in studies of specimens from oral cavity and from nonoral sites in which an infection with B. asacacharolyticus of oral origin may have taken place. It is suggested that antibodies reactive with the oral antigenic type of B. asaccharolyticus be included in the preparative procedure of the Fluoretec-M reagent.

Pathogenicity testing of Macaca arctoides subgingival plaque following chlorhexidine treatment

POTENTIAL INFECTIVITY of subgingival plaque of Macaca arctoides in guinea pig leg muscle was examined before, during, and after chlorhexidine treatment. The regime of chlorhexidine administration did not appear to alter the monkey subgingival microflora markedly and had no demonstrable effects on the pathogenicity of the subgingival plaque. These data confirm previous suggestions that chlorhexidine essentially does not penetrate into the deeper part of periodontal pockets following a supragingival mode of administration.

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.

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.

Microbial composition of monkey dental plaque (Macaca arctoides and Macaca fascicularis)

The supragingival and subgingival dental plaque flora of Macaca arctoides and Macaca fascicularis monkeys were examined using mylar strip impressions, direct smears, and culture techniques. In smears, samples generally contained 40--50% cocci, 20--30% rods 8--20% fusiform bacteria, and 4--5% each of filaments, vibrios and spirochetes. Differences in the ratios of the various bacterial groups related to age and sex were found. Several monkey bacterial species were similar to those in human dental plaque. The present results indicate that the Macaca female monkey can be a suitable animal model for the experimental studies of dental diseases.

Ultrastructure of the subgingival microflora in juvenile periodontitis

The ultrastructure of the subgingival deposits on the root surfaces of teeth affected by juvenile periodontitis was studied on 12 teeth from nine individuals, 15--30 years of age. The deposits consisted of either microbial masses associated with a pellicle, or of a cuticular material almost free of bacteria. Gram-negative rods and filaments were the predominant microorganisms. "Corncob" configurations consisting of filamentous bacteria surrounded by Gram-positive cocci, and "bristle brush" formations comprising corncobs surrounded by long rods were observed in the superficial layer of the plaque. Spirochetes and flagellated rods constituted a major segment of the microflora. The present data indicated that the deep pockets in juvenile periodontitis harbor a sparse but relatively characteristic microbial population.

Microbiota of gingivitis in man

A study on the predominant cultivable microorganisms inhabiting gingival crevices affected with a chronic gingivitis was carried out using the roll tube culture technique. Samples were obtained from nine individuals 25--42 years of age. Gram-positive rods make up 29.1% of the isolates and included mainly Actinomyces naeslundii, Actinomyces israelii, and Actinomyces viscosus. Streptococcus mitis and Streptococcus sanguis together made up 26.8% of the cultivable organisms. Peptostreptococcus averaged 3.0% of the organisms recovered. Gram-negative anaerobic rods constituted 25.0% of the total isolates with Fusobacterium nucleatum, Bacteroides melaninogenicus ss. intermedius. Bacteriodes ochraceus, other Bacteroides species, Selenomonas sputigena, and Campylobacter sputorum as the most predominant isolates. Haemophilus parainfluenzae averaged about 14% and Veillonella species 4.3% of the cultivable microflora. The data presented indicate that the subgingival microflora of a chronic gingivitis differs from those of healthy periodontium and advanced adult and juvenile periodontis. This might suggest that different infectious processes may be operative in various clinical entities of periodontal disease.

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

This investigation examined the ability of cells of Bacteroides melaninogenicus subsp. asaccharolyticus 381 to adhere to surfaces that might be important for its initial colonization of the mouth and its subsequent colonization in periodontal pockets. Of 48 asaccharolytic strains of B. melaninogenicus, 47 agglutinated human erythrocytes, whereas none of 20 fermentative strains, which included reference cultures of the subspecies intermedius and melaninogenicus, were active. Electron microscopy indicated that both asaccharolytic and fermentative strains possessed pili; hence, the presence of pili did not correlate with the hemagglutinating activities of B. melaninogenicus strains. Both asaccharolytic and fermentative B. melaninogenicus strains suspended in phosphate-buffered saline adhered in high numbers to buccal epithelial cells and to the surfaces of several gram-positive bacteria tested, including Actinomyces viscosus, A. naeslundii, A. israelii, Streptococcus sanguis, and S. mitis. B. melaninogenicus subsp. asaccharolyticus 381 also attached, but in comparatively low numbers, to untreated and to saliva-treated hydroxyapatite. Addition of clarified whole saliva to suspensions of strain 381 almost completely eliminated adherence to buccal epithelial cells and to hydroxyapatite surfaces, but saliva had no detectable effect on attachment to gram-positive plaque bacteria. Both fermentative and nonfermentative strains of B. melaninogenicus also attached in high numbers to crevicular epithelial cells derived from human periodontal pockets, but normal human serum strongly inhibited attachment. Serum also inhibited attachment of strain 381 to saliva- and serum-treated hydroxyapatite, but it had little effect upon attachment to gram-positive bacteria. These observations suggested that salivary and serum components would strongly inhibit the attachment of B. melaninogenicus cells to several oral surfaces, but not to the surfaces of certain gram-positive bacteria commonly present in human dental plaque. This was confirmed by an in vivo experiment in which streptomycin-labeled cells of B. melaninogenicus 381-R were introduced into the mouths of two volunteers. After 10 min, several hundred-fold higher numbers of the organism were recovered from preformed bacterial plaque present on teeth than from clean tooth surfaces or from the buccal mucosa and tongue dorsum. High numbers of B. melaninogenicus cells were also recovered from preformed plaque after 150 min, but virtually no cells of the organism were recovered from the other surfaces studied. These data suggest that the presence of dental plaque containing Actinomyces and other gram-positive bacteria may be essential for the attachment and colonization of B. melaninogenicus cells after their initial introduction into the mouth. Similarly, the presence of subgingival plaque containing gram-positive bacteria may be necessary for its secondary colonization in periodontal pockets.

Microflora in the healthy gingival sulcus in man

The roll tube culture technique was utilized to examine quantitatively and qualitatively the predominant cultivable microflora inhabiting the clinically healthy gingival sulcus. Seven periodontists aged 32-54 years were included in the study. From a total of 350 isolates, 85 (24.3%) were obligate anaerobes, 53 (15.0%) were Gram negative, and 197 (56.3%) were categorized as rods. Actinomycetes predominated in three samples. Four samples were dominated by Streptococcus species. The flora as revealed in the present study comprised a markedly lower proportion of Gram-negative organisms than that found at the base of deep periodontal pockets.

The predominant cultivable microflora of advanced periodontitis

A study on the predominant cultivable microorganisms harbored in the base of deep periodontal pockets of eight patients aged 34-48 years was carried out using the roll tube culture technique. From a total of 475 isolates, 425 (89.5%) were obligate anaerobes, 356(74.9%) were Gram-negative, and 441(92.8%) were categorized as rods. Bacteroides melaninogenicus and Fusobacterium nucleatum constituted the majority of the isolates in seven samples, but their mutual proportions differed considerably between the samples. One sample was dominated by Actinomyces species. Some periodontopathic potentials of the predominating Gram-negative rods are summarized.

The predominant cultivable organisms in juvenile periodontitis

Quantitative and qualitative examinations of the predominant cultivable microflora of the advanced tissue destruction (pocket) associated with juvenile periodontitis and of control pockets without loss of attachment were carried out by using anaerobic tube culture technique. The microflora from the control sites consisted primarily of streptococci, Gram-negative rods, and Gram-positive rods. In contrast, the test pockets had a relatively stable and characteristic microflora, dominated by various Gram-negative, anaerobic rods. The Gram-negative rods were divided into main groups, but a satisfactory classification of many of these microorganisms could not be performed with the methods used and the data available. The predominating Gram-negative rods differed from individual to individual. The role of the Gram-negative rods in the etiology of juvenile periodontitis is unknown. Some potential pathogenic mechanisms of these microorganisms are discussed.

Comparison of five growth media and two anaerobic techniques for isolating bacteria from dental plaque

Five agar media in combination with the Hungate roll tube technique and conventional anaerobic jar technique (Baird & Tatlock¿ jars) were evaluated to determine the most suitable medium for non-selective isolation of the viable microorganisms in dental plaque. The highest colony count was obtained by using "Modified Medium 10" with the roll tube technique. About twice as many plaque colonies were recovered by roll tube technique as by the conventional anaerobic technique. With the MM 10 roll tube technique, 7 d of incubation revealed only 93% of the colonies that could be detected after 14 d of incubation.