Serologically reactive dextrans were synthesized from sucrose by 22 of 48 strains of streptococci isolated from the blood of patients with subacute bacterial endocarditis. One strain formed an appreciable amount of levan as well as dextran. Nine strains of group H streptococci from throats formed dextran serologically similar to that formed by the described endocarditis streptococci. Six strains of S. salivarius from throats and feces, which were included for comparison, formed levan which agreed in serological properties with the purified levan previously described for one strain of that species.
The experimental method comprised a series of serological tests that were controlled and supplemented by physical and chemical tests, and furnished a relatively simple but entirely adequate way of recognizing and distinguishing dextrans and levans in bacterial cultures without isolation of the purified polysaccharides. The possible use of dextran and levan formation in the differential description of non-hemolytic streptococci is suggested.