Screening vaccine candidate strains against Streptococcus agalactiae of tilapia based on PFGE genotype

► Streptococcus agalactiae strains with identical PFGE type showed similar immunogenicity. ► The immunogenicity differed among strains with different PFGE type. ► The immunogenicity was not only associated with strain serotype. ► Cannot obtain a single vaccine candidate strain that can protect all strains of serotype Ia.