Streptococci with dual antigen specificity for Lancefield groups D and G.

Streptococci have been isolated which may be identified in serological tests as belonging to Lancefield group G, but in fact belong to group D. Twenty-two cultures with this property were obtained from four countries; they included Streptococcus bovis and Streptococcus durans as well as Streptococcus faecalis. Selected strains were studied in serological tests and cross-absorption procedures, in which it was found that the group G reaction given by these isolates is due to an epitope with at least partial identity with reference group G antigen. Identification of an enterococcus as a group G streptococcus could lead to erroneous and ineffective chemotherapy. Antibiotic sensitivity testing of streptococcus group G isolates should be a routine procedure, and bile-aesculin and salt-tolerance testing of these isolates would be a wise precaution.