Relationships among Actinomyces naeslundii (A. viscosus) Bacteriophages Isolated from Sewage and the Oral Cavity

Abstract

Several lytic phages of Actinomyces naeslundii genospecies 2 (formerly A. viscosus) have been isolated from sewage and from dental plaque. To define the relationships between these phages and ultimately to assess their role in the ecology of the human oral cavity, 13 phages isolated from these two environments were purified and their biochemical properties compared. Five small, short-tailed phages, isolated from sewage over the course of several years (Av-1, Av-2, Av-3, 1281, and BF307) were morphologically indistinguishable from each other and from five phages recovered more recently from human dental plaque (CT1, CT2, CT3, CT6 and CT7). The small phages (all morphotype C1) contained double-stranded linear DNA, 18 kb in size. In contrast, three phages from dental plaque (CT4, CT5 and CT8) possessed longer tails and much larger head structures (morphotype B1). Two of the larger phages (CT4 and CT5) contained DNA genomes estimated to be 80 kb in size, whereas large phage CT8 contained DNA of approximately 50 kb. Restriction endonuclease analysis revealed extensive differences between the large and small phages but the latter group showed similar, and in several cases identical, fragment patterns. These results indicate the existence of at least three distinct types of lytic bacteriophage active against oral Actinomyces spp. The similarities between the sewage and small dental plaque isolates indicate a high degree of relatedness and suggest that the sewage phages probably originated from the oral cavity.

Key Words:

• Actinomyces
• bacteriophages
• oral phages
• dental plaque