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