Caerin 1.1 and 1.9 peptides from Australian tree frog inhibit antibiotic-resistant bacteria growth in a murine skin infection model

Host-defence caerin 1.9 peptide was originally isolated from skin secretion of Australian tree frog, and inhibits the growth of a wide range of bacteria in vitro. In this study, we demonstrated that caerin 1.9 shows high bioactivity against several bacteria strains, such as Staphylococcus aureus, Acinetobacter Baumannii, methicillin-resistant Staphylococcus aureus (MRSA), and Streptococcus hemolyiicus in vitro. Importantly, unlike antibiotic Tazocin, caerin 1.9 does not induce bacterial resistance after 30 rounds of in vitro culture. Moreover, caerin 1.1, another peptide of caerin family, has additive antibacterial effect when used together with caerin 1.9. Furthermore, caerin 1.1 and 1.9 prepared in the form of a temperature sensitive gel inhibit MRSA growth in skin bacterial infection model of two murine strains. These results indicate that caerin 1.1 and 1.9 may have the advantage than conventional antibiotics against bacterial infection of skin.