Authors: Ujszegi, János; Boros, Zsófia;Fodor, András;Hettyey, Attila;

Chytridiomycosis, caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd) has caused extreme losses in amphibian biodiversity. Finding bacteria for probiotic therapy with the purpose of disease mitigation which produce metabolites with antifungal properties may turn out to be invaluable in the fight against chytridiomycosis. The entomopathogenic bacterium, Xenorhabdus szentirmaii produces secondary metabolites that are effective against a wide range of fungal plant pathogens. To assess whether it may also be effective against Bd, we extracted cell-free culture media (CFCM) from liquid cultures of X. szentirmaii and tested their disinfecting efficacy at dilutions of 10 and 2 %, while also measuring possible malign effects on juvenile common toads (Bufo bufo) experimentally infected with Bd or sham infection. We detected no negative treatment consequences on the survival and body mass of uninfected toads. However, among infected individuals, survival was higher and infection intensity was lower due to the 10 % CFCM treatment, compared to toads treated with no, or 2 % CFCM solution. Efficacy is likely due to the fabclavines but this needs to be verified. Nonetheless, these results support the potential of using X. szentirmaii metabolites in the development of a new, non-invasive, chemical-free, and cheap method for Bd disinfection.