Serogrouping single colonies of beta-hemolytic streptococci from primary throat culture plates with nitrous acid extraction and Phadebact streptococcal reagents.

The serogrouping of isolated beta-hemolytic streptococcal colonies from throat cultures by a micronitrous acid extraction method employing Phadebact Streptotoccus Test reagents was compared with results obtained with the direct-plate Phadebact procedure and the autoclave and Streptomyces albus enzyme-lysozyme extraction methods. These data were compared with those from the Lancefield grouping obtained with a capillary precipitin test. The micronitrous acid extraction method was modified to yield an uncomplicated method that provides specific coagglutination responses from one beta-hemolytic streptococcal colony that may be collected from a primary blood agar plate either on the end of an applicator stick or from a sweep of an inoculating loop from mixed growth.