PRF1 and bacterial infectious disease: It has been reported that S. iniae was positive for a variety of virulence determinants, including enzyme phosphoglucomutase, capsular polysaccharide, polysaccharide deacetylase, and the cytolysin streptolysin S, which make significant contribution to overcome host immune system, avoid phagocytic uptake, promote cellular adherence and invasion, as well as induce cell death after bacterial infection (Deng et al., 2017).