Microbiological parameters associated with IL-1 gene polymorphisms in periodontitis patients

Background, aims: Polymorphisms in the cluster of IL-1 genes have been sign ificantly associated with the severity of adult periodontitis. The purpose of this study was to compare microbiological parameters in IL-1 genotype ne gative and positive adult subjects with a range of periodontitis severities . Method: The study included 108 subjects in good general health. Clinical pa rameters were recorded at 6 sites/tooth excluding 3rd molars and included: plaque accumulation, gingival erythema, bleeding on probing, suppuration, p ocket depth and attachment level. Subgingival plaque samples were collected from the mesiobuccal surface of up to 28 teeth in each subject (mean 25.3) providing a total of 2736 samples. The levels of 40 subgingival taxa were determined in each sample using checkerboard DNA-DNA hybridization. Fingers tick blood samples were collected for IL-1A (+4845) and IL-1B (+3954) genot yping using PCR-based methods. Results: The proportion of IL-1 genotype positive subjects that exhibited m ean counts of specific subgingival species above selected thresholds was si gnificantly higher than the proportion of genotype negative subjects. Promi nent among species that were detected at higher levels in genotype positive subjects were members of the "red" and "orange" complexes and included: Ba cteroides forsythus, Treponema denticola, the Fusobacterium nucleatum subsp ecies, Fusobacterium periodonticum, Campylobacter gracilis, Campylobacter s howae and Streptococcus constellatus. Streptococcus intermedius, Streptococ cus gordonii and 3 Capnocytophaga species were also detected more frequentl y at high numbers in genotype positive subjects. Significantly higher mean counts of B. forsythus, Porphyromonas gingivalis, T. denticola, the F. nucl eatum subspecies, F. periodonticum, Campylobacter rectus, C. showae, Eubact erium nodatum, S. constellatus, S. gordonii, and S. intermedius were detect ed at periodontal pockets >6 nun in subjects who were genotype positive whe n compared with genotype negative subjects. The increase was due to increas ed numbers of cells of these species rather than a major shift in proportio n. Conclusion: The data suggest that genotype positive subjects more frequentl y had higher revels of "red" and "orange" complex species that are known to be strongly associated with measures of periodontal inflammation.