Identification of group D streptococci by SeroSTAT.

Clinical isolates of group D streptococci presumptively identified by biochemical methods were grouped by latex agglutination using a commercially prepared reagent specifically sensitized with group D antiserum (SeroSTAT; Scott Laboratories, Inc., Fiskeville, R.I.). Streptococcus species tested included S. faecalis, S. faecium, S. durans, S. avium, S. bovis, and S. equinus. Colonies of the organism to be tested were picked from agar plates, emulsified in a drop of glycine-buffered saline on a slide, and mixed with a drop of the latex reagent. Macroscopic agglutination occurred within 60 s. A total of 115 isolates of group D streptococci were tested; 103 (89.6%) gave positive reactions with SeroSTAT. Twelve strains failed to react with the latex reagent; these 12 strains also gave negative results with group D antiserum when tested by the Lancefield method. Two of 14 group A streptococci also reacted with the SeroSTAT group D reagent; after trypsinization, the cross-reaction was eliminated. Group B streptococci, viridans group streptococci, anaerobic streptococci, and staphylococci all gave negative reactions with the SeroSTAT reagent. The SeroSTAT reagent is a useful diagnostic tool for the prompt identification of enterococcal and non-enterococcal group D streptococci.