Synergistic antifungal activity of KB425796-C in combination with micafungin against Aspergillus fumigatus and its efficacy in murine infection models

KB425796-C is a novel Antifungal metabolite produced by the newly isolated Bacterial strain Paenibacillus sp. No. 530603. This compound is a 40-membered macrocyclic lipopeptidolactone consisting of 12 Amino acids and a 3-hydroxy-15-methylpalmitoyl moiety. KB425796-C displayed Antifungal activity against micafungin-resistant fungi and was fungicidal to Trichosporon asahii in vitro. In a murine systemic Infection model of T. asahii, KB425796-C showed excellent efficacy upon i.p. administration at 32 mg kg(-1). In addition, KB425796-C induced morphological changes in the hyphae of Aspergillus fumigatus and had fungicidal effects in combination with micafungin. In a mouse model of septic A. fumigatus Infection, although non-treated mice survived for a maximum of only 6 days, the survival rate of micafungin-treated mice (0.1 mg kg(-1)) increased to 20%, while the survival rate of mice treated with a combination of micafungin (0.1 mg kg(-1)) and KB425796-C (32 mg kg(-1)) increased to 100% during the 31-day post-infection period. Our findings suggest that KB425796-C is a good candidate for the treatment of aspergillosis in combination with micafungin.