beta (beta)-hemolytic streptococci

be·ta (β)-he·mo·lyt·ic strep·to·coc·ci

(bā'tă hē'mō-lit'ik strep-tŏ-kok'sī)
Those that produce active hemolysins (O and S) that cause a zone in the blood agar medium in the area of the colony; β-hemolytic streptococci are divided into groups (A to O) on the basis of cell wall C carbohydrate (see Lancefield classification); Group A includes strains that cause human infections such as streptococcal pharyngitis, impetigo, erysipelas, otitis media, and wound infections and can stimulate production of autoimmune globulins that cause acute rheumatic fever and acute glomerulonephritis. Induced are more than 20 extracellular substances elaborated by strains of beta-hemolytic streptococci including erythrogenic toxin (elaborated only by lysogenicstrains), deoxyribonuclease (streptodornase), hemolysins (streptolysins O and S), hyaluronidase, and streptokinase.