302
1LI. A. GERENCSER
with other species than do serotype 2 strains. Antigenic variation among
strains of serotype 1 has been shown by FA (Brock and Georg, 1969;
Slack et al., 1969) and by immunodiffusion tests (Bowden and Hardie,
1973), but at present these differences are not thought suficient to warrant
further serotype differentiation. Brock and Georg (1969) reported that
95% of the clinical isolates submitted to the Center for Disease Control for
identification belonged to serotype 1. I n contrast, Holmberg (1976)
isolated serotype 2 more frequently than serotype 1 in a study of dental
plaque flora. Further study is needed to determine the actual proportions
of the two serotypes in the normal oral flora and in clinical disease.
T A B L E V I I
Cross-reactions of Actinomyces naeslundii serotypes
F I T C conjugated antiserum
-
A.
naeslundii
Actinomyces
A.
A.
A.
Antigens
1 2
3
type 963
1
1
2
SP .
israelii
viscosus
viscosus
A. naeslundii, 1 W
10
E
A. naeslundii, 2 mt W
-
A. naeslundii, 3 mt
-
-
-
mt
-
-
[Ilt
Actinomyces sp.
-
-
type 963
m e -
M, Homologous reaction.
m, Reciprocal cross-reaction.
E, One-way cross-reaction.
-, Negative.
t, Cross-reaction usually high titred ; other cross-reactions are low-titred; all
cross-reactions are strain variable.
Three serotypes of A. naeslundii (Table VII) have been reported, but
only serotype 1, as represented by strain ATCC 12104, has been studied
to any extent. Our studies of A. naeslundii serotype 1 show antigenic
differences within the serotype analogous to those 'seen in A. israelii
serotype 1. Some of the variant strains which can be separated from type 1
by absorption may represent new serotypes, but as with A. israelii, at
present these strains are included in serotype 1.
Serotype 2 of A. naeslundii was described by Bragg et al. in 1972 on the