Koala cathelicidin PhciCath5 has antimicrobial activity, including against Chlamydia pecorum

Devastating fires in Australia over 2019–20 decimated native fauna and flora, including koalas. The resulting population bottleneck, combined with significant loss of habitat, increases the vulnerability remaining koala populations to threats which include disease. Chlamydia is one disease causes morbidity mortality predominant pathogenic species, pecorum , severe ocular, urogenital reproductive tract In marsupials, koala, gene expansions an antimicrobial peptide family known as cathelicidins have enabled protection immunologically naïve pouch young during early development. We propose that are active against other bacteria fungi. Here we describe ten cathelicidins, five contained full length coding sequences were widely expressed tissues throughout body. Focusing on these five, investigate their activity two C . isolates from distinct serovars; MarsBar IPTaLE, well One cathelicidin, PhciCath5, inactivated IPTaLE elementary bodies significantly reduced number inclusions compared control (p<0.0001). Despite evidence cathelicidin expression within be infected by natural PhciCath5 concentrations may inadequate vivo prevent or infections also displayed fungi Gram negative positive bacteria, methicillin-resistant Staphylococcus aureus (MRSA). Electrostatic interactions likely drive adherence pathogen cell membrane, followed membrane permeabilisation leading death. Activity E coli was presence 10% serum 20% whole blood. Future modification enhance activity, serum/blood, provide a novel solution infection koalas species.