Development of coagglutination reagents for serological grouping of streptococci

Coagglutination reagents for the rapid serological grouping of groups A, B, C, F and G Streptococcus have been developed. Antisera to groups A, B, C, F and G Streptococcus were raised in rabbits. After absorption with cross-reacting antigens, the specific antibodies were coated on Staphylococcus protein-A and used as group-specific coagglutination reagents. The sensitivity of the reagents for groups A, C and G Streptococcus was 100 per cent and the specificity was 100, 100, and 98.77 per cent, respectively. The sensitivity and specificity of these reagents were consistent up to 12 months, although specificity declined with longer storage. The in-house coagglutination reagents for groups A, C and G streptococcus were also tested in comparison with the commercially available Streptococcus Phadebact test and yielded almost identical results. Sensitivity of the in-house of group B Streptococcus reagent was low, while the group F reagent gave a high incidence of false positive reaction.