Comprehensive Characterization of a Streptococcus agalactiae Phage Isolated from a Tilapia Farm in Selangor, Malaysia, and Its Potential for Phage Therapy

The outbreak in tilapia has caused huge losses in the aquaculture industry worldwide. In Malaysia, several studies have reported the isolation of , but no study has reported the isolation of phages from tilapia or from the culture pond. Here, the isolation of the phage from infected tilapia is reported and it is named as vB_Sags-UPM1. Transmission electron micrograph (TEM) revealed that this phage showed characteristics of a and it was able to kill two local isolates, which were smyh01 and smyh02. Whole genome sequencing (WGS) of the phage DNA showed that it contained 42,999 base pairs with 36.80% GC content. Bioinformatics analysis predicted that this phage shared an identity with the S73 chromosome as well as several other strains of , presumably due to prophages carried by these hosts, and it encodes integrase, which suggests that it was a temperate phage. The endolysin of vB_Sags-UPM1 termed Lys60 showed killing activity on both strains with varying efficacy. The discovery of the temperate phage and its antimicrobial genes could open a new window for the development of antimicrobials to treat infection.