The reactions of streptococci and lactobacilli in blood agar

Abstract

The phenomena produced by colonies of streptococci on blood-agar plates have long been used by medical bacteriologists for classification purposes. An examination of the literature showed that only a few contradictory data were available for the corresponding phenomena induced by the saprophytic lactic acid bacteria. A systematic investigation into the types of “haemolysis” and discoloration phenomena produced by typed cultures of lactic acid bacteria was therefore carried out to ascertain whether the blood-agar plate was of any use in the routine classification of these bacteria. The monograph of Brown (1919), which has been generally accepted as the standard work on the subject, is regarded as a standard of reference in the present paper.