Ribotyping shows intrafamilial similarity in Actinobacillus actinomycetemcomitans isolates.

This study reports ribosomal RNA gene restriction patterns of 54 Actinobacillus actinomycetemcomitans isolates obtained from 9 families (12 children and 11 parents). The isolates represented serotypes a, b, c and d. The chromosomal DNA extracted from A. actinomycetemcomitans isolates was digested with the restriction endonucleases EcoRI, BamHI, HindIII, ClaI and Bg/I. The DNA fragments were hybridized to the rrnB ribosomal RNA operon of the Escherichia coli chromosome. In 5 families, isolates belonging to the same family (mother and/or father and the children) had identical hybridization patterns when analyzed with all 5 enzymes. In 3 families, each family member harbored only one ribotype of A. actinomycetemcomitans, but at least one member harbored isolates that were of a different ribotype than the other members of the family. In one family, the mother harbored 2 ribotypes (and serotypes), one common with the daughter and one different. In conclusion, the study confirms the previous results that A. actinomycetemcomitans is transmitted intrafamilially.