A. Macheleidt et al., Clonal diversity of Actinobacillus actinomycetemcomitans isolates from young adults with minimal periodontal disease, J PERIOD RE, 34(4), 1999, pp. 179-187
Actinobacillus actinomycetemcomitans is a major periodontal pathogen which
is associated with both early-onset periodontitis and adult cases refractor
y to conventional periodontal therapy, although the organism has also been
shown to be widely distributed among dentate healthy individuals. The obser
ved disease status may be associated with a variation in virulence of diffe
rent strains or clones. The aim of the present study was to analyse genotyp
e distribution as assessed by an arbitrarily primed polymerase chain reacti
on (AP-PCR) among 51 isolates of A. actinomycetemcomitans recovered from mo
re than 200 young adult recruits with no or minor periodontal disease. In a
ddition, isolates from 25 periodontitis patients as well as reference strai
ns were genotyped. Primers amplifying (i) a specific sequence in the ltxA r
egion, (ii) a specific 16S rRNA sequence and (iii) sequences in the leukoto
xin promoter region were used to verify species identity of the strains. Th
ree random oligonucleotide primers were employed to analyse genomic polymor
phisms of the organism by means of PGR. A total of 19 genotypes could be di
stinguished, which were grouped by cluster analysis into 5 major clusters b
ased on genetic similarity and a complete linkage sort. Whereas 3 clusters
assembled A. actinomycetemcomitans genotypes isolated from both healthy sub
jects and periodontitis patients, one cluster containing 4 different genoty
pes exclusively comprised isolates from healthy or gingivitis subjects. Ano
ther cluster with 2 genotypes consisted of strains originating from periodo
ntitis patients (p < 0.05). One strain characterized by a specific 530 bp d
eletion in the promoter region of the leukotoxin region was identified in a
Ghanese patient with localized juvenile periodontitis. It was concluded th
at there is considerable clonal diversity of A. actinomycetemcomitans strai
ns isolated from healthy or periodontally diseased subjects, and that genet
ically closely related groups might be associated with health or disease.