Journal of Dental Research, Vol 64, 1039-1045, Copyright © 1985 by International & American Associations for Dental Research Online Journals
Antigenic variation of indigenous streptococci
J. E. Beem, W. B. Clark and A. S. Bleiweis
Isolates of Group D streptococci indigenous to the murine oral cavity were
studied to detect the occurrence of antigenic variation. Group D
streptococci cultured from molar homogenates of Balb/c mice were randomly
selected for study on the basis of distinctive colony morphology. Isolates
obtained over a 12-week period were biotyped using the API 20S system, and
subjected to Lancefield extraction and rocket immunoelectrophoresis for
serotyping. All isolates were compared with an arbitrarily selected
standard test strain (W1S-1) isolated the first week of the first
experimental series. Four biotypes were encountered during the first week
of two experimental series. Two very unusual biotypes detected during the
first experimental series persisted throughout that series, as did two more
common biotypes throughout the second experimental series. Anti-W1S-1 serum
produced three precipitin bands (antigens O, D, and K) against W1S-1
Lancefield extract and against the respective biotypes detected during the
first week of the two series. Of the three antigens detected, only the
group antigen (D) did not vary during either experimental series. Antigenic
variants lacking the O or K antigen and bearing these distinctive
phenotypes were repeatedly isolated in subsequent weeks. Ultimately, 16% of
190 strains isolated during the first series and 26% of 167 strains
isolated during the second series proved to be antigenic variants of the
predominant biotypes detected in both series.
