Lancefield’s classification recognizes 20 serogroups, designated by the letters A to H and K to V. It should be noted that Lancefield groups do not necessarily correspond to streptococcal species. Members of a single species may belong to more than one Lancefield group, and a single Lancefield group may include different species. Some streptococcal species lack Lancefield group antigens, and others have not yet been described. The ABIS database includes species from the genera Streptococcus, Enterococcus, Lactococcus, Melissococcus, and Vagococcus.