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Lancefield classification

a serologic classification dividing haemolytic streptococci into groups (a to O) which bear a definite relationship to their sources, based upon precipitation tests depending upon group-specific substances that are carbohydrate in nature; e.g., group A contains strains pathogenic for man; B, strains from mastitis in cows and from normal milk, including a few strains from the human throat and vagina; c, strains from various lower animals, including a number from cattle; D, strains from cheese; E, strains from certified milk; f, strains mainly from the human throat, associated with tonsillitis; g, strains from man, a few from monkeys and dogs; and H, k, and O, nonpathogenic strains from normal human respiratory tracts.