Abstract
Summary
A flocculation test for detection and measurement of type-specific antibody to Group A streptococci has been evaluated. A single strain of each of 3 serological types of streptococcus was employed. When a suspension of bentonite particles between 1.0 and 1.5 μ in size was exposed to an unad-sorbed homologous rabbit antiserum after being coated with partially purified M protein antigen, flocculation was obtained. The highest homologous flocculation titer encountered was 1-32. A weak non-reciprocal cross-reaction between types 36 and 14 M antigens was found: while M antigen of strain S-94 (type 36) did not react with anti-S-23 (type 14) antisera, M protein of strain S-23 exhibited some cross-reactivity with anti-S-94 antisera. The test antigen could be stored at 4°C for at least 6 weeks without loss of potency. No group-specific or type-specific flocculation occurred when the test antigen was prepared by exposing the bentonite particles to a crude antigen mixture, obtained by hot HCl extraction of streptococcal cells, which was shown by precipitin tests to contain large amounts of both group-specific and type-specific antigens. Partially purified M protein obtained from such a mixture, however, could be used to sensitize particles, which were then reactive with antisera. No flocculation was observed when bentonite particles treated with group-specific polysaccharide solution were exposed to homologous group-specific antiserum.
Get full access to this article
View all access options for this article.