Double-Zone Beta-Hemolytic Streptococci

Abstract

Double-zone [beta]-hemolytic streptococci occur in the throats and vaginae of many normal persons. They are also a common cause of mastitis in cows. These streptococci fall into 3 fermentative groups: lactose [long dash], salicin + ; lactose +, salicin [plus or minus]; and lactose +, salicin [long dash]. All of the 188 strains examined belong to Lancefield''s serological group B by the precipitin test. In man, the lactose [long dash], salicin + and the lactose +, salicin + strains may assume the role of opportunist pathogens, producing infections in various parts of the body and rarely may cause fatal septicemia. The source of such infections may usually be traced to the throat or genitourinary tract. There is no evidence that these streptococci are of epidemic significance. In cows, the lactose +, salicin + and the lactose +, salicin[long dash]strains are common causes of mastitis. The lactose [long dash], salicin + strains have not been found in cows although they are capable of producing mastitis when inoculated into the udder. In attempts to eradicate mastitis from dairy herds the human carrier of these streptococci should be considered. The recognition of the double-zone hemolytic streptococci supplies additional reason why diagnostic laboratories should no longer report all hemolytic streptococci as Streptococcus hemo-lyticus, a term which is inadequately informative and of doubtful validity as a specific name.