SOD1 and infection: At 48 h post-infection (Figure 7), CGMCC3.2055-treated larvae had the highest SOD activity, exceeding other strains and CK; CFCC81428 and CK had the lowest SOD activity (p < 0.05) with no intergroup difference; and Bb01 and bio-21738 had lower SOD activity than CGMCC3.2055 (p < 0.05).