Presumptive speciation of Streptococcus bovis and other group D streptococci from human sources by using arginine and...

A simplified method for speciation of group D streptococci is described. A total of 4,156 streptococcal isolates from human clinical material was tested for ability to hydrolyze esculin in the presence of 40% bile, ferment pyruvate, hydrolyze arginine, and grow in media containing 40% bile or 6.5% NaCl. Streptococci which hydrolyzed esculin in 40% bile, but which did not hydrolyze arginine, were also tested for their ability to ferment raffinose or sorbose. Sixty percent (2,503) of the isolates hydrolyzed esculin in the presence of 40% bile and were thus presumptively identified as group D. By application of the other criteria, 84% of these were speciated as Streptococcus faecalis, 7% were speciated as S. faecium, 6% were speciated as S. bovis, 2% were speciated as S. avium, and 1% were not identified. This scheme was shown to be both reliable and practical for use in the diagnostic laboratory. S. avium and S. bovis isolates were characterized, and 18 S. bovis isolates from patients with bacterial endocarditis were compared physiologically with 151 isolates of this species from other sources.