The serological classification ofStreptococcus cremoris

Attempts to produce in rabbits group N sera for Streptococcus cremoris , using suspensions of living, disintegrated and heat-treated bacterial cells, yielded only non-specific products, cross-reactions occurring most commonly and intensively with HCl extracts of the streptococci of groups K and L. 2. The non-specific antibodies in these sera were completely removed by absorption with streptococci of group K or L, the group N reactions being only partially impaired. 3. In order to inactivate, before immunizing rabbits, that antigen in the ‘cremoris’ cells responsible for stimulating the production of non-specific antibodies, the organisms were ‘absorbed’ with an excess of group K or L antiserum. 4. With suspensions of organisms treated in this way, potent group N specific precipitating sera were obtained for both freshly isolated and freeze-dried strains of Str. cremoris. 5. The identity of Str. cremoris with serological group N is thus established.