VI. IDENTIFICSTION OF ACTINOM YCES ANU UHACHNIA
303
basis of four strains which cross-reacted with both A. naeslundii serotype 1
and A. viscosus serotype 2. Three of the strains were similar to serotype 1,
while the fourth strain (CDC W 1544) seemed to be more closely related to
A. viscosus serotype 2 (L. Georg, pers. comm.). In a more recent report,
Bragg et al. (1975) determined that only the last strain (W 1544) should be
considered serotype 2 and that the other three strains should be considered
untyped. I n our studies of the four original serotype 2 strains, we also
found that three of them were closely related to serotype 1 and by our
criteria would be considered serotype 1 variants while the fourth strain
(W 1544, WVU 1523) was definitely different. Thus, our results confirm
those of Bragg et al. (1975). Only two or three additional strains of serotype
2 have been identified.
Jordan et al. (1974) described strain N16 (WVU 820) as a new serotype
of A. naeslundii serotype 3. This strain is more closely related to serotype 2
than to serotype 1. Like serotype 2, one of the problems in studying this
serotype is the very small number of strains available. We now have five
additional strains in our collection which belong to serotype 3. These
strains cross-react strongly with serotype 2 (W 1544) but like N16 can be
separated from it by absorption.
Cross-reactions between A. naeslundii serotypes and other species are
shown in Table VII. A. naeslundii serotype 1 shows a wide range of crossreactions which are highly strain dependent and vary with the particular
lot of antiserum being used. I n general, A. naeslundii, serotype 1 strains
cross-react with A. israelii serotype 1 and with both serotypes of A.
viscosus (Lambert et al., 1967; Slack et al., 1969; Slack and Gerencser,
1975). Serotypes 2 and 3 show high titred cross-reactions with A. viscosus
serotype 2.
A group of organisms, listed in Tables VI and VII as Actinomyces sp.
serotype 963 must be considered at this point. I n a study of dental plaque
isolates, we found a group of eight strains of Actinomyces which fell into
a clearly delineated serological group. These organisms had some biochemical reactions resembling A. israelii, but their overall pattern of
reactions was more nearly that of A. naeslundii. When these strains were
first described (Gerencser and Slack, 1976), they were tentatively designated A. naeslundii serotype 4. Since we now feel that it was premature to
give this group a species name, we have included them in tables showing
reactions of both A. naeslundii and A. israelii under the accession number
of the strain used for antiserum production as Actinomyces sp. serotype
963. The serotype 963 strains cross-react with A. israelii serotype 1 and
A. naeslundii serotype 1 and have a weak one-way cross-reaction with A.
naeslundii serotype 2. Unlike the A. naeslundii serotypes, Actinomyces sp.
serotype 963 has very limited cross-reactions with A. viscosus serotype 2.
303
basis of four strains which cross-reacted with both A. naeslundii serotype 1
and A. viscosus serotype 2. Three of the strains were similar to serotype 1,
while the fourth strain (CDC W 1544) seemed to be more closely related to
A. viscosus serotype 2 (L. Georg, pers. comm.). In a more recent report,
Bragg et al. (1975) determined that only the last strain (W 1544) should be
considered serotype 2 and that the other three strains should be considered
untyped. I n our studies of the four original serotype 2 strains, we also
found that three of them were closely related to serotype 1 and by our
criteria would be considered serotype 1 variants while the fourth strain
(W 1544, WVU 1523) was definitely different. Thus, our results confirm
those of Bragg et al. (1975). Only two or three additional strains of serotype
2 have been identified.
Jordan et al. (1974) described strain N16 (WVU 820) as a new serotype
of A. naeslundii serotype 3. This strain is more closely related to serotype 2
than to serotype 1. Like serotype 2, one of the problems in studying this
serotype is the very small number of strains available. We now have five
additional strains in our collection which belong to serotype 3. These
strains cross-react strongly with serotype 2 (W 1544) but like N16 can be
separated from it by absorption.
Cross-reactions between A. naeslundii serotypes and other species are
shown in Table VII. A. naeslundii serotype 1 shows a wide range of crossreactions which are highly strain dependent and vary with the particular
lot of antiserum being used. I n general, A. naeslundii, serotype 1 strains
cross-react with A. israelii serotype 1 and with both serotypes of A.
viscosus (Lambert et al., 1967; Slack et al., 1969; Slack and Gerencser,
1975). Serotypes 2 and 3 show high titred cross-reactions with A. viscosus
serotype 2.
A group of organisms, listed in Tables VI and VII as Actinomyces sp.
serotype 963 must be considered at this point. I n a study of dental plaque
isolates, we found a group of eight strains of Actinomyces which fell into
a clearly delineated serological group. These organisms had some biochemical reactions resembling A. israelii, but their overall pattern of
reactions was more nearly that of A. naeslundii. When these strains were
first described (Gerencser and Slack, 1976), they were tentatively designated A. naeslundii serotype 4. Since we now feel that it was premature to
give this group a species name, we have included them in tables showing
reactions of both A. naeslundii and A. israelii under the accession number
of the strain used for antiserum production as Actinomyces sp. serotype
963. The serotype 963 strains cross-react with A. israelii serotype 1 and
A. naeslundii serotype 1 and have a weak one-way cross-reaction with A.
naeslundii serotype 2. Unlike the A. naeslundii serotypes, Actinomyces sp.
serotype 963 has very limited cross-reactions with A. viscosus serotype 2.