Objective To investigate the prevalence of H.actinomycetemcomitans in Chinese chronic periodontitis （CP） patients and periodontally healthy adults. Methods 116 chronic periodontitis patients and 111 periodontally healthy adults were included. In each CP patient, subgingival plaque samples were collected from two sites of different molars with the greatest probing depth（PD）and one periodontally healthy site（PD≤3mm）. The samples of periodontally healthy adults were obtained from the mesio- buccal site of one first upper molar. Bacteria DNA were extracted for detection of H.actinomycetemcomitans by 16S rRNA PCR. Results The prevalence for H.actinomycetemcomitans of diseased sites（33.62%）was significantly higher than that of healthy sites from CP patients（0.86%）and the periodontally sites（0.90%）（P0.05）. A decreasing trend of H.actinomycetemcomitans was observed as the age increased. And the pocket depth and clinical attachment losswas associated with the occurrence of H.actinomycetemcomitans in a positive mode. And H.actinomycetemcomi - tans was more often detected in the bleeding sites on probing. Conclusion H.actinomycetemcomitans was more frequently detected in periodontitis sites than periodontally healthy sites. For CP patients, a higher prevalence was associated with the seriously involved sites than those moderate and mild implicated sites. H.actinomycetemcomitans is considered to be the one of the periopathogens involved in the etiology of chronic periodontitis.
