Red bacterial complex is associated with the severity of chronic periodontitis in a Thai population

BACKGROUND: The distribution of periodontal pathogens differs in various geographic locations and racial/ethnic groups. This study investigated the microbiological features of chronic periodontitis (CP) patients in Thailand. METHODS: Subgingival plaque samples from 20 non-periodontitis subjects, 20 patients with mild CP, and 20 patients with moderate to severe CP were examined using polymerase chain reaction (PCR) to identify Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola, and Aggregatibacter actinomycetemcomitans. RESULTS: In the moderate to severe CP patients, there was high prevalence of P. gingivalis (95%), T. forsythia (95%), T. denticola (80%), as well as the red complex (coexistence of all three species at the same lesion) (75%). A. actinomycetemcomitans was detected in only 35% of the patients in this study group. P. gingivalis was detected in as high as 45% of the non-periodontitis controls. CP and disease severity were significantly related to the presence of T. forsythia together with T. denticola and the red complex. The red complex was not found in any non-periodontitis site. CONCLUSION: Red complex bacteria were predominant periodontal pathogens of the moderate to severe form of CP in this Thai population. The presence of T. forsythia together with T. denticola, and the red complex species at the same site were significantly associated with the disease severity.