Group identification of streptococci. Evaluation of three rapid agglutination methods.

The clinical need to rapidly and correctly differentiate beta-hemolytic streptococci into Lancefield groups has prompted the commercialization of rapid agglutination methods. Three serogrouping kits, Phadebact, Sero STAT, and Streptex, were compared with the classic precipitin technic. One hundred and fifty beta-hemolytic streptococci and 75 alpha-hemolytic streptococci isolated from clinical specimens were used. Phadebact grouped all beta-hemolytic strains correctly while Sero STAT and Streptex were 96.7% and 99.3% accurate, respectively. Phadebact and Streptex correctly identified all group D streptococci. Commercial agglutination reagents represent a simple and reliable method for grouping streptococci.