Prevalence of Actinobacillus actinomycetmcomitans in an ethnic adult Chinese population

Aim: The aim of this study was to determine the prevalence and the structur e of the leukotoxin promoter region of Actinobacillus actinomycetemcomitans in an ethnic Chinese population. Method: Subgingival plaque samples were collected from 42 patients with mod erate to advanced periodontitis and 50 periodontally healthy patients. A. a ctinomycetemcomitans was detected directly from the crude subgingival plaqu e by PCR using leukotoxin gene specific primers. The presence of A. actinom ycetemcomitans was determined by a single 285 bp PCR amplicon. Results: A. actinomycetemcomitans was found to be present in the subgingiva l plaque of 68 out of a total of 92 patients examined (74%). 29 out of the 42 periodontitis patients tested were carriers of A. actinomycetemcomitans (69%). Among the periodontally healthy patients studied, 39 out of 50 subje cts possessed the bacteria (78%). PCR analysis of the promoter region of th e ltx operon revealed that none of the 42 moderate to advanced periodontiti s patients examined harboured A. actinomycetemcomitans strains with the JP2 -like promoter of the ltx operon, known to enhance leukotoxin expression. 2 out of the 27 advanced periodontitis patients clinically diagnosed as suff ering from rapidly progressive periodontitis were found to be carriers of t he mildly toxic strain of A. actinomycetemcomitans with the characteristic 652-like promoter. Conclusions: The high prevalence of A. actinomycetemcomitans, regardless of whether the subgingival samples were analysed from patients with healthy o r diseased periodontium suggests that this bacterial species is part of the normal oral flora of ethnic Chinese. Our preliminary results also suggeste d that subjects who harboured the mildly toxic strain of A. actinomycetemco mitans were potentially susceptible to aggressive forms of periodontitis.