The JP2 genotype of Aggregatibacter actinomycetemcomitans and marginal periodontitis in the mixed dentition

To perform a cross-sectional study on the carrier frequency of JP2 and non-JP2 genotypes of A. actinomycetemcomitans in Moroccan school children and relate the presence of these genotypes to the periodontal status in the mixed dentition.

A plaque sample from 513 children was analysed by PCR. JP2 genotype-positive subjects (n = 46), an equally sized group of non-JP2 genotype-positive subjects, and an A. actinomycetemcomitans-negative group were randomly chosen among the remaining subjects for clinical and radiographic examination.

Among 513 children, 46 (9.0%) carried the JP2 genotype and 186 (36.3%) were positive for non-JP2 genotypes, whereas A. actinomycetemcomitans could not be detected in the remaining 281 subjects. Among 75 subjects with mixed dentition and selected for clinical examination, clinical attachment loss (CAL) ≥ 3 mm at two or more periodontal sites on primary teeth was found in the JP2 genotype-positive group only. In total, 6.7% of subjects with primary teeth present showed CAL ≥ 3 mm at two or more sites.

The carrier frequency of the JP2 genotype of A. actinomycetemcomitans was at a comparable level to frequencies previously found in Moroccan adolescent populations. Clinical attachment loss, manifesting already in the primary dentition, was found only in the group of Moroccan children carrying the JP2 genotype of A. actinomycetemcomitans.