Isosorbide and Chytridiomycosis in Panamanian Golden Frogs

Abstract

Global amphibian decline is an established problem, first noted over 40 years ago. Without an obvious cause beyond the natural factors, such as habitat loss, disease has risen as a reasonable explanation. Chytridiomycosis is an infectious disease targeting amphibians, namely frogs, in Central and South America. The fungus, Batrachochytrium dendrobatidis, has been shown to be inhibited by natural mixes of antimicrobial peptides (AMPs) found on the backs of susceptible and resistant frogs. A unique case, Atelopus zeteki, does not show the same use of AMPs. Rather, a heterocyclic diol, isosorbide, seems to be involved in their immunological response to B. dendrobatidis infection. Using liquid chromatography mass spectrometry, gas chromatography mass spectrometry, flame ionization detection, and chytrid bioassays, isosorbide was determined and suggested to function in an antimicrobial manner in A. zeteki. The lowest concentration exhibiting antimicrobial properties was 250 mM isosorbide against chytrid zoospores. The case study of A. zeteki is illustrative of how future infectious diseases’ activity could be quenched before such drastic losses occur. Additional research is needed to identify the antimicrobial properties of isosorbide in a quantitative manner and for determining whether the frog or the topical bacteria on the frog are synthesizing this compound.