VI. IDENTIFICATION OF ACTIh'OMYCES AND ARACHNIA
301
Each of the species, except A. meyerii, has been divided into at least two
serotypes based on FA reactions. The serotypes of A. bovis show little or no
cross-reaction with each other although cross-reactions have been shown
by immunodiffusion (Georg et al., 1964). Among the strains studied, all
serotype 2 strains produce filamentous microcolonies (rough A. bovis) while
serotype 1 strains produce smooth microcolonies.
Most isolates of A. odontolyticus do not cross-react with other Actinomyces (Slack and Gerencser, 1975; Holmberg and Forsum, 1973). I n 1971,
Slack, Landfried, and Gerencser reported the isolation of a second serotype
of A. odontolyticus which had a strain-variable, low-titred cross-reaction
with serotype 1 strains and a strong cross-reaction with A. viscosus,
serotype 1 antiserum. The existence of serotype 2 has been confirmed by
T A B L E V I
Cross-reactions of Actinomyces israelii serotypes
FITC conjugated antiserum
A.
A.
A.
A.
Actinomyces
israelii
israelii
naeslundii viscosus
SP.
Antigens
1
2
1
2
type 963
-
-
-
A. israelii, 1
A. israelii, 2
Actinomyces sp.
-
-
type 963
., Homologous reaction.
m, Reciprocal cross-reaction ; all cross-reactions are strain variable and generally
low-titred.
Holmberg and Nord (1975) and Bragg and Kaplan (1976). Bragg and
Kaplan (1976) found a one-way cross-reaction between the A. odontolyticus
serotypes and confirmed the cross-reaction between A. odontolyticus,
serotype 2 and A. viscosus, serotype 1 antiserum.
Two serotypes of A. israelii were reported by Lambert et al. (1967) and
later confirmed by Brock and Georg (1969) and by S,lack et al. (1969).
The cross-reactions of A. israelii serotypes are shown in Table VI. Our
studies and those of Holmberg and Forsum (1973) indicate a reciprocal
cross-reaction between the two serotypes while Brock and Georg (1969)
found only a one-way cross-reaction in which serotype 1 conjugates
stained serotype 2 antigens. Serotype 1 strains show more cross-reactions