Streptococcus iniae is a major Gram-positive aquatic pathogen that is associated with invasive disease outbreaks in cultured fish worldwide, which can lead to severe symptoms with high mortality rates of up to 50％, thereby causing substantial economic losses for the global aquatic industry.The identification of potential virulence determinants of streptococcal infections will help to understand and control this disease, but only a few have been confirmed in S.iniae.