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The prevalence of Actinobacillus actinomycetemcomitans isolates was examined in a rural population of southern Thailand. Sixty individuals aged 30-39 and 50-59 years were randomly selected from a group of 363 persons, living in four villages, who had been clinically examined previously. A subgingival plaque sample was taken with a curette from the mesial aspect of the two upper and lower first molars. Each sample was dispersed in 3.3 ml of VMGA III transport medium and spread onto Trypticase Soy Broth with Bacitracin and Vancomycin (TSBV)-agar plates on the same day. After incubation in 10% CO2 for 5 days the plates were examined for typical A. actinomycetemcomitans colonies which were tested for catalase activity. Each strain was further tested for biochemical characteristics, serotyped against serotype-specific antisera a-e and ribotyped after DNA digestion using the restriction endonucleases HindIII and EcoRI. For 53 (88%) of the 60 individuals, A. actinomycetemcomitans was present in at least one subgingival sample, which is considerably higher than the prevalence in Western European adults. In 11 individuals, two or three different strains were found. Serotypes a and c were the most prevalent, and serotype b was found only once among 46 tested isolates. Eleven ribotypes were found among the 46 strains. While the same ribotype could be found among individuals of the same village, no ribotype of A. actinomycetemcomitans was unique for individuals of any one village. The study demonstrated a high prevalence of A. actinomycetemcomitans among adults of the rural population of southern Thailand and indicates that this species is present as part of the resident oral flora in this population.

The present investigation explored the genotypic heterogeneity of Porphyromonas gingivalis using restriction endonuclease analysis and ribotyping of 64 P. gingivalis isolates, recovered from the periodontal pockets of 3 beagle dogs, 2 of which were reared together. The isolates originated from both healthy and periodontal disease affected sites and thereby enabled the study of bacterial genotype with respect to (i) individual host, (ii) ecological niche (site within host) and (iii) level of periodontal health. Whole genomic DNA was extracted from each isolate and digested by the restriction endonuclease KpnI. Digestion fragments were separated by electrophoresis and transferred onto nylon membranes. The blots were hybridized with a digoxigenin-labeled 16S rDNA probe, and hybridization bands were detected using an anti-digoxigenin antibody conjugated with alkaline phosphatase and enhanced chemiluminescence. Fourteen genomic fingerprints and 13 ribotypes were observed among the 64 isolates. As many as 8 distinct fingerprints were detected within a single host and up to 4 fingerprints within a single periodontal pocket. The dogs reared together shared 2 common clonal types but also exhibited clonal types unique to each dog. No clear association between clonal type and periodontal health status could be made. The results revealed an extensive intra-host genotypic heterogeneity of P. gingivalis strains in the beagle dog and indicated that ribotyping was a sensitive method for differentiating clonal types within species.

The aim of this study was to describe the presence of some microbial species in the subgingival microflora of a randomly selected subject sample. A further objective was to analyze the association between some microbiological characteristics and the periodontal conditions of the subjects. A total of 171 individuals aged 30-65 years were included. A pooled subgingival plaque sample was obtained from the mesial aspect of the 6 Ramfjord teeth by the use of the paper-point method. The samples were processed and analyzed according to standardized procedures. The periodontal condition of the subjects was examined clinically and included assessment of plaque, gingivitis, probing pocket depth and probing attachment level. The results showed that 81% of the subjects were positive for Campylobacter rectus, 80% for Fusobacterium nucleatum, 77% for Streptococcus sanguis, 72% for Streptococcus mitis, 66% for Eikenella corrodens, 58% for Prevotella intermedia, 32% for Capnocytophaga, 27% for Selenomonas, 25% for Actinobacillus actinomycetemcomitans, 14% for Porphyromonas gingivalis and 13% for Streptococcus mutans. Small differences in the periodontal conditions were observed between subjects harboring P. gingivalis, A. actinomytecomitans or > 5% P. intermedia and the rest of the sample. Similarly small differences in the clinical parameters were revealed when the subjects were grouped according to proportions of disease-associated and health-associated species in their subgingival samples.