The human-derived serotype Ⅴ ST1 GBS strains NNA038 and NNA048 was isolated from a amniotic fluid of full-term pregnant woman who suffered from premature rupture of membrane in China.Serotype Ia ST7 GBS strain YM001 is an attenuated strain ,its parent strain HN016 was isolated from an outbreak epidemical disease in tilapia from China.HN016_KO_D2 is a knockout strain from Serotype Ia ST7 GBS strain HN016.