Fish Streptococcosis is one of re-emerging infectious bacterial diseases of freshwater and marine fishes economically affecting the sustainability of aquaculture development worldwide (Fig 1) (Mishra et al., 2018). The bacterium has been isolated from water and from the gastrointestinal (GI) tracts of various vertebrate and invertebrate animals. Therefore, it’s an opportunistic bacterial disease that occur in stressed fishes. (Streptococcosis can occur in warm water, and mainly the causative agent is Strept. iniae, L. garvieae, Strept. agalactiae, and Strept. parauberis, meanwhile cold water streptococcosis (below 15°C) is caused mostly by V. salmoninarum and L. piscium (Domenech et al., 1996).

In Egypt, Strept. iniae was isolated from Nile tilapia (Younes et al., 2019), Strept. agalactiae and Strept. dysagalactiae subsp. dysgalactiae (Abu-Elala et al., 2020), L. garvieae (El-daim et al., 2023a), E. faecalis (Elgohary et al., 2021).