Injection of the pathogenic bacteria to grass carp, pre-exposed to PSNAP (80 nm diameter, 10–1,000 μg/L), showed enhancement in the enzymatic activities of CAT, SOD, and GST, and MPO and MDA contents were enhanced in the oxidative stress-related mechanisms in the grass carp gut after bacterial infection (Li Z. et al., 2024). Here, MPO is linked to bacterial infectious disease.