Intragenomic recombination in the highly leukotoxic JP2 clone of Actinobacillus actinomycetemcomitans

The highly leukotoxic; JP2 clone of Actinobacillus actinomycetemcomitans is strongly associated with aggressive periodontitis in adolescents of African descent. DNA fingerprinting using the frequently cutting restriction enzyme MspI and multilocus sequence typing (MLST) showed that five strains of this clone were genetically virtually identical, although ribotyping of the six rrn genes and EcoRl RFLP analysis of the seven IS 150-like elements revealed differences. PCR analyses demonstrated that these multi-copy sequences are subject to intragenomic homologous recombination, resulting in translocations or large inversions. The genome rearrangements were reflected in differences among 25 strains representing the JP2 clone in DNA fingerprinting using the rare-cutting restriction enzyme Xhol and resolved by PFGE. Xhol DNA fingerprinting provides a tool for studying local epidemiology, including transmission of this particularly pathogenic clone of A. actinomycetemcomitans.