Arcanobacterium hemolyticum is a Gram positive bacillus that invades the pharynx and the skin.
Growth occurs best on agars enriched with human or rabbit blood.
Growth is slow and hemolytic colonies may not be visible until 48-72 hours after inoculation. Serologic tests for antibodies are available in research facilities but are not available commercially. The laboratory should be advised that the organism is suspected in order to process the sample correctly. Beta hemolysis on sheep blood agar is less intense than with GAS and may be overlooked in cultures with heavy growth of normal bacterial flora. The rash may be scarlitinaform but circumoral pallor is absent.