Rapid Test for Detecting Lactic Streptococcal Agglutinins in Cheese Milk

Abstract

A Rose bengal-stained antigen plate testing procedure was developed for detecting lactic streptococcal agglutinins in milk. Colostrum samples were used as sources for immunoglobulins G and M. Results were positive from 2% packed cell volumes of heat-killed Rose bengal-stained cells suspended in .5 molar Tris maleate buffer (pH 7.0). Lactic streptococcal antigens were susceptible to immunoglobulins G and M. Streptococcus lactis strain C2 was not an agglutination resistant organism but among 15 strains tested was the least susceptible when exposed to low concentrations of agglutinins.Stained antigens reacted with equal effectiveness when tested against colostrum whey (pH 7.0) or whey samples prepared from cheese milk to detect agglutinins. The indirect immunoassay revealed the specificity of immunoglobulin G to clump starter cells in contrast to immunoglobulin M. For example, Streptococcus lactis C2 was agglutinated by G but did not conjugate well with M. The immunoassay testing also revealed a potential procedure for detecting lactic streptococcal agglutinins. Autoclaving milk prior to adding agglutinin-containing whey dramatically reduced agglutination of starter strains.