TLR9 and infection: In the kidney, a significant upregulation of most TLR genes (nearly all TLRs, including TLR1, TLR2, TLR4, TLR5, TLR8, TLR9, TLR13, TLR18 and TLR22) were observed (Figure 7A), particularly at 6 and 12 h post-infection, suggesting a rapid and sustained immune response in A. hydrophila.