OCCURRENCE OF TEMPERATE BACTERIOPHAGES IN DIFFERENT ACTINOBACILLUS-ACTINOMYCETEMCOMITANS SEROTYPES ISOLATED FROM PERIODONTALLY HEALTHY-INDIVIDUALS

The occurrence of temperate bacteriophages was studied in 34 isolates of Actinobacillus actinomycetemcomitans derived from 27 periodontally healthy Finnish individuals both by lysis/plaque assays and by DNA hyb ridizations. In addition the serotype, the ribotype and the arbitraril y primed polymerase chain reaction (AP PCR) profile were determined fo r each A. actinomycetemcomitans strain. Fourteen isolates showed hybri dization patterns very similar to that of a known lysogen when probed with the genome of the previously characterized temperate phage Aa phi 23. Only 6 of these 14 strains had produced lysis or single plaques o n suitable indicator strains. Phage Aa phi 247 derived from one of the se lysogens was indistinguishable from Aa phi 23 by electron microscop y, and the genomes showed highly related DNA hybridization patterns. T he remaining 20 isolates exhibited hybridization patterns very differe nt from that of Aa phi 23 DNA. Seven of these strains also gave lysis or single plaques, suggesting that 21 of the 34 strains were lysogenic . These data indicate that the prophages per se do not represent a vir ulence factor exclusively associated with periodontal disease. Presenc e of an Aa phi 23-related prophage correlated with serotype a and AP-P CR type 1 of the bacterial host. This may indicate that Aa phi 23 and related phages have a limited host range.