Whole cell proteins (WCPs) and extracellular proteins (ECPs) were extracted and concentrated (Yin et al. 2018 (link)). Overnight cultures of E. piscicida were sub-cultured into 50-mL fresh DMEM and statically incubated for 24 h to 72 h at 28 °C; bacteria were then harvested by centrifugation at 5,000 × g for 10 min at 4 °C for WCPs. For ECPs, culture supernatants were filtered with 0.22-µm filters (Millipore, USA), and concentrated using 10 kDa cutoff centrifugal filter devices (Millipore, USA). Proteins were separated by 12% SDS-PAGE, followed by Coomassie blue staining. For western blots, separated proteins were wet transferred onto PVDF membranes (Millipore, USA) and incubated with a 1:1000 dilution of mouse anti-EseB (GL Biochem, China). HRP-conjugated anti-mouse IgG (Santa Cruz Biotechnology, CA) was used at a 1:2,000 dilution as a secondary antibody. Proteins were visualized with TMB substrate (Amresco, USA). Mouse anti-DnaK (Santa Cruz Biotechnology, USA) was used as a loading control.