Distribution of bacterial clusters among periodontal patients

Methods: This study was based on the databank of a commercial laboratory that provides diagnostic testing services in different European countries (IAI PadoTest 4.5®, Institute for Applied Immunology, Zuchwil, Switzerland). The presence of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Tannerella forsythensis and Treponema denticola as well as the total bacterial content was quantified using oligonucleotide probes in subgingival plaque samples collected in patients with various periodontal conditions. Five types of bacterial associations were identified by cluster analysis. The distribution of bacterial clusters among the study population was then determined. A total of 33,259 samples collected in 10,946 patients was included in the final analysis.

Results: Mean age of patients was 46.2 ± 11.3 years and mean probing depth was 6.8 ± 2.0 mm. Cluster 1, characterized by low counts of all species, was associated with shallow pockets; its frequency of detection was unrelated to patient age. Cluster 4, characterized by a predominance of A. actinomycetemcomitans, tended to be found in deep pockets in patients < 26 years. Cluster 5, characterized by high counts of P. gingivalis, T. forsythensis and T. denticola but low counts of A. actinomycetemcomitans, was detected in deep pockets in patients ³ 46 years. Analysis using the subject as the unit showed that 25 % of the subjects presented only one cluster type; 52 % of the subjects harbored two cluster types while only 2 % of them had four different clusters.

Conclusion: Five different bacterial associations were identified by cluster analysis. The distribution of cluster types was influenced by age and by clinical probing depth. Cluster types tended to aggregate within patients.