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Appl Environ Microbiol. 1971 August; 22(2): 171-176
Copyright © 1971 American Society for Microbiology. All Rights Reserved.

Production of Double Zones of Hemolysis by Certain Strains of Hemolytic Streptococci of Groups A, B, C, and G on Heart Infusion Agar

Division of Infectious Diseases, Department of Medicine, Stanford Medical Center, Stanford, California 94305

ABSTRACT

This report describes the appearance of a double zone of hemolysis around surface colonies of certain strains of streptococci of groups A, B, C, and G incubated aerobically on sheep blood-Heart Infusion Agar. The occurrence of the altered hemolytic pattern was related to peroxide production by the organism. Anaerobic conditions and the incorporation of catalase into the agar abolished the double-zone pattern and caused reversion of the organisms to a beta-hemolytic pattern. The double-zone pattern can be confused with alpha hemolysis on surface growth.