Aim of study:Passive immunization using pathogen-specific antigen is a potential method for preparation of specific antibody,which is significant to diagnosis and prevention of diseases.The objective of this study is to prepare and identify egg yolk immunoglobulin (IgY) against β-hemolyticus streptococcus for diagnosis and prevention of diseases caused by β-hemolytic streptococcus.Material and methods:The β-hemolyticus streptococcus were obtained from Guangdong Institulte of Micribiology.Female chickens were maintained in the Liangsha hennery in Guangzhou.Freunds complete adjuvant and Freunds incomplete adjuvant (Sigma-Aldrich,America),bovine serum albumin (BSA,Weijia,China),anti-chicken IgY HRP conjugate (G135A,Promega,USA),3,3,5,5-Tetramethylbenzidine(TMB) were used in this study.All other chemicals of analytical reagent grade were from local companies.Specific IgY was prepared by hens immunized with p-hemolytic streptococcus and was extracted from the yolks of eggs by polyethylene glycol two-step precipitation.The purity and the content of IgY were tested by sodium dodecyl sulfate polyacrylamined gel electrophoresis (SDS-PAGE) and Bradford method,the activities of IgY were evaluated by Enzyme-Iinked immunosorbent assay (ELISA),bacteriostatic test and agar gel diffusion test.Results:The purity of IgY could reach 95% with a yield of 108 mg of IgY per egg in the study.And the titer was 1:5120,which could remain for 50 days.According to the agar diffusion test and bacteriostatic test,IgY could combine with p-hemolytic streptococcus specifically and inhibit the growth of p-hemolyticus streptococcus in vitro.Conclusions:The current work suggested that this specific IgY was potential as a therapeutic treatment for diagnosis and prevention of diseases caused by β-hemolytic streptococcus.