<i>Xenopus laevis</i> as an infection model for human pathogenic bacteria

Animal infection models are essential for understanding bacterial pathogenicity and corresponding host immune responses. In this study, we investigated whether juvenile <i>Xenopus laevis</i> could be used as an infection model for human pathogenic bacteria. <i>Xenopus</i> frogs succumbed to intraperitoneal injection containing the human pathogenic bacteria <i>Staphylococcus aureus</i>, <i>Pseudomonas aeruginosa</i>, and <i>Listeria monocytogenes</i>. In contrast, non-pathogenic bacteria <i>Bacillus subtilis</i> and <i>Escherichia coli</i> did not induce mortality in <i>Xenopus</i> frogs. The administration of appropriate antibiotics suppressed mortality caused by <i>S. aureus</i> and <i>P. aeruginosa</i>. Strains lacking the <i>agr</i> locus, <i>cvfA</i> (<i>rny</i>) gene, or hemolysin genes in <i>S. aureus</i>, LIPI-1-deleted mutant of <i>L. monocytogenes</i>, which attenuate virulence within mammals, exhibited reduced virulence in <i>Xenopus</i> frogs compared with their respective wild-type counterparts. Bacterial distribution analysis revealed that <i>S. aureus</i> persisted in the blood, liver, heart, and muscles of <i>Xenopus</i> frogs until death. These results suggested that intraperitoneal injection of human pathogenic bacteria induces sepsis-like symptoms in <i>Xenopus</i> frogs, supporting their use as a valuable animal model for evaluating antimicrobial efficacy and identifying virulence genes in various human pathogenic bacteria.