Reading and Interpretation
A beta-hemolytic reaction is interpreted as complete clearing around the colony. An alpha-hemolyic reaction is interpreted as greening around the colony and gamma hemolysis is interpreted as no change in the media surrounding the colony. The hemolytic reaction on blood agar is complex and subject to many variables. For the complete explanation and interpretation of the reactions the reader is referred to the 1977 publication, CDC Laboratory Update, Isolation and Identification of Streptococci. Part I. Collection, Transport, and Determination Hemolysis, Annex 1. Application of the interpretations of the hemolytic reactions for streptococci described in the Update to the other genera should not be a problem.