The Journal of Medical Microbiology, Vol 21, Issue 3 189-197, Copyright © 1986 by Society for General Microbiology
Differentiation of Streptococcus sanguis and S. mitior by whole-cell rhamnose content and possession of arginine dihydrolase
T. Price, G. L. French, H. Talsania and I. Phillips
Whole-cell rhamnose concentrations were measured in 48 strains of
streptococci resembling Streptococcus sanguis and S. mitior. Physiological
characteristics were tested by the API-20/Strep system, and it was found
that "typical" S. sanguis (arginine positive, aesculin positive) contained
significant amounts of rhamnose, while "typical" S. mitior (arginine
negative, aesculin negative) contained very low or undetectable amounts of
rhamnose. Both groups contained dextran-positive and dextran-negative
strains. Organisms that were more difficult to speciate (those giving
positive results in the arginine or the aesculin test, but not in both)
could also be divided into a rhamnose-positive and a rhamnose-negative
group; with one exception, all of the rhamnose-positive strains gave a
positive result with arginine in the API-20/Strep test. There were several
discrepancies between the results of conventional tests for arginine and
aesculin hydrolysis and those of the corresponding API test. The results of
conventional tests for arginine hydrolysis did not correlate closely with
rhamnose content, and conventional tests for aesculin hydrolysis were less
sensitive than API tests. With the API-20/Strep system, S. sanguis can
almost always be distinguished from S. mitior by its ability to hydrolyse
arginine.
