In vitro and in vivo susceptibility of two-drug and three-drug combinations of terbinafine, itraconazole, caspofungin, ibuprofen and fluvastatin against Pythium insidiosum.

The present study investigated the in vitro inhibitory activity of terbinafine, itraconazole, caspofungin, fluvastatin and ibuprofen against 15 isolates of Pythium insidiosum in double and triple combinations and determined in vivo correlations using rabbits with experimental pythiosis. The minimal inhibitory concentration (MIC) was determined in accordance with the Clinical and Laboratory Standards Institute M 38-A2 protocol (2008), and the in vitro interactions were evaluated using a checkerboard microdilution method. For the in vivo study, 20 rabbits inoculated with P. insidiosum zoospores were divided into four groups: group 1 was treated with terbinafine and itraconazole; group 2 was treated with terbinafine, itraconazole and fluvastatin; group 3 was treated with terbinafine and caspofungin; and group 4 was the control group. Combinations of terbinafine with caspofungin or ibuprofen were synergistic for 47% of the isolates, and antagonism was not observed in any of the double combinations. The triple combinations were mostly indifferent, but synergism and antagonism were also observed. In the in vivo study, the histological aspect of the lesions was similar among the groups, but group 2 showed the lowest amount of hyphae and differed significantly from the other groups.