Evaluation of a modified nitrous acid extraction latex agglutination kit for grouping beta-hemolytic streptococci and enterococci.

The rapid and accurate identification of the Lancefield group of beta-hemolytic streptococci and enterococci is an important procedure in clinical laboratories. Latex agglutination techniques are more rapid and technically less demanding than traditional extraction-precipitation methods. Prolex (Pro-Lab Diagnostics, Richmond Hill, Ontario, Canada) is a latex agglutination kit which contains modified nitrous acid reagents to extract antigens and can be used to detect group D antigen in streptococci and enterococci, as well as group A, B, C, F, and G antigens. A total of 302 strains of streptococci and enterococci were tested with this kit. All streptococci of groups A (41 strains), B (39 strains), C (35 strains), D (3 strains), F (10 strains), and G (48 strains) were correctly grouped, as were 125 (97%) of 129 strains of enterococci. Prolex is a reliable method for grouping the beta-hemolytic streptococci and enterococci most frequently encountered in clinical laboratories.