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The increasing serotypic diversity and multidrug resistance of Riemerella anatipestifer pose a serious threat to the poultry industry, necessitating novel antimicrobial agents. Although phage-derived endolysins offer rapid and specific bactericidal activity with low resistance potential, their efficacy against this Gram-negative pathogen is severely constrained by the outer membrane barrier, driving the need for strategies to enhance endolysin penetration. In this study, the native endolysin NA of phages vBRanSCRP2 was verified to lack antibacterial activity. To overcome this barrier, we constructed three chimeric proteins—ALC001, ALC005, and ALC007—by fusing a receptor-binding protein, a cell-penetrating peptide, or a polycationic nonapeptide, respectively. All three chimeras exhibited dose-dependent antibacterial activity, with ALC005 demonstrating the best performance. ALC005 achieved a lytic rate of 72. 2% against the tested Riemerella anatipestifer strains, remained stable at 0–40 °C and pH 6–9, and was shown by transmission electron microscopy to exert its bactericidal effect by disrupting the bacterial cell envelope and inducing cell lysis. Collectively, cell-penetrating peptide fusion is a reliable and effective strategy to potentiate endolysin activity against Riemerella anatipestifer.
Chen et al. (Fri,) studied this question.