FIMBRIAL-MEDIATED COLONIZATION OF MURINE TEETH BY ACTINOMYCES-NAESLUNDII

Groups of mice fed diets high in sucrose or glucose were orally inocul ated with 10(10), 10(9) or 10(8) colony-forming units of one of the fo llowing Actinomyces naeslundii strains possessing the type 1 (T1(+))) and/or the type 2 (T2+) fimbriae: T14V-J1 (T1+, T2+), 5519 (T1+), 5951 (T2+), and 147 (non-fimbriated). Ninety-six hours after inoculation t heir upper jaws were cultured to look at the implantation of each of t hese strains on the teeth. In mice fed a sucrose diet, regardless of t he presence or absence of fimbriae, each bacterial strain colonized 10 0% of the mice at the highest inoculation doses of the infecting organ ism. But at a dose of 10(8), T14V-J1 was the only strain which coloniz ed 100% (12/12) of the mice, 5519 colonized 10/11, 5951 colonized 9/11 and 147 colonized 7/11. These differences were not statistically sign ificant. When mice were fed a high-glucose diet, 100% infection was ac hieved with strains T14V-J1, 5519 and 5951 only at the highest dose of 10(10) colony-forming units. Strain 147 colonized in 8/9 of the mice at that dosage. At lower dosages, no bacterial strain implanted in 100 % of the mice. In the glucose experiment at a dose of 10(8), strains e xpressing the T1 fimbriae implanted significantly better than strains without the T1 fimbriae. At a dose of 10(9) colony-forming units, the parent strain T14V-J1 implanted significantly better than strains with out the T1 fimbriae. Similarly, strain: 5519 (T1+) implanted significa ntly better than 5951 and implanted better than 147, although the diff erence was not significant. These results suggest that while the prese nce of the T1 and T2 fimbriae may confer some advantage in the establi shment of these organisms in vivo, even the strains without fimbriae w ere able tb colonize. Strains T14VJ1 and 5519 were found to bind well to hydroxyapatite treated with mouse saliva, while strains 5951 and 14 7 did not. Only T2 fimbriated strains T14-V-J1 and 5951 exhibited a la ctose-reversible coaggreation with indigenous strains of enterococci t hat may contribute to the elevated levels of colonization of strain 59 51 in vivo.