Rapid solubilization and grouping of antigens from beta-hemolytic streptococci via a centrifugal analyzer

The precipitin reaction between antigens from groups A, B, C, and G betahemolytic streptococci and group-specific antisera was monitored quantitatively by a turbidimetric assay on a centrifugal analyzer. A grouping procedure is described in which antigens from standardized concentrations of bacteria taken directly from agar plates are extracted by Streptomyces albus enzyme at 52 C during a 20-min incubation and then multiple samples assayed in 4 min. Because all components of the system are quantitatively standardized via a spectrophotometer, subjectivity common to other grouping methods is reduced, and high levels of quality assessment can be ensured by establishing numerical control limits. One hundred isolates were assayed using group-specific antisera for A, B, C, and G (400 samples), and 100% correct positive identification with no false positive was obtained. The assay can also serve as a simple way for commercial sources to provide activity information for their products.