In vitro combination with doxycycline plus antifungals against clinical Mucorales pathogens

Purpose Since systematic antifungals for mucormycosis showed variable MICs depending on strains, effective and safe antifungal therapy was still needed. This study is aimed to evaluate the in vitro activity of doxycycline combined with antifungal therapy against dominant Mucorales pathogens. Methods Multidrug susceptibility testing was performed with doxycycline and antifungals, including itraconazole, posaconazole, and amphotericin, in 21 isolates of 8 dominant Mucorales pathogens. Results The fractional inhibitory concentration index according to M38 showed one Rhizopus arrhizus isolate synergic ( ∑ FICI = 0.375) and other isolates in addition (0.5 <  ∑ FICI < 4). Conclusions Doxycycline was found to have in vitro advantages in combined antifungal treatment over antifungals alone.