One limitation of this study is that we only focused on the gene expression of certain genes, which may omit other important molecules, especially lysozyme and complement component 3 which might partially contribute to survival; moreover, antimicrobial peptides, c-reactive protein, protease inhibitors, pentraxins, and transferrin (71), which are also known to participate in the defense of bacterial infection, should be further investigated. This evidence concerns the gene CRP and bacterial infectious disease.