In vitro assays on the susceptibility of four species of nematophagous fungi to anthelmintics and chemical fungicides/antifungal drug.

Wang, Bobo; Zhang, Nan; Gong, Pengtao; Li, Jianhua; Wang, Xiaocen; Li, Xin; Wang, Fenghui; Cai, Kuizheng; Zhang, Xichen

Using nematophagous fungi for the biological control of animal parasitic nematodes will become one of the most promising strategies in the search for alternative chemical drugs. The purpose of this study was to check the in vitro activity of four anthelmintics, four chemical fungicides, and two antifungal drugs on the spore germination of nematophagous fungi: Duddingtonia flagrans (SF170), Arthrobotrys oligospora (447), Arthrobotrys superba (435), and Arthrobotrys sp. (PS011). A modified 24-well cell culture plate assay was conducted to evaluate the susceptibility of nematophagous fungi against drugs tested by calculating the effective middle concentrations (EC50 ) of each tested drug to inhibit the germination of fungal spores. EC50 ranged between 0.7 and 47.2 μg/mL for fenbendazole, thiabendazole, and ivermectin, except levamisole (546.5-4057.8 μg/mL). EC50 of tested fungicides was 0.6-2.3 μg/mL for carbendazim, 55.9-247.4 μg/mL for metalaxyl, 24.4-45.2 μg/mL for difenoconazole, and 555.9-1438.3 μg/mL for pentachloronitrobenzene. EC50 of two antifungal drugs was 0.03-3.4μg/mL for amphotericin B and 0.3-10.9 μg/mL for ketoconazole. The results showed that ten tested drugs, except for levamisole and pentachloronitrobenzene, had in vitro inhibitory effects on nematophagous fungi. The chlamydospores of D. flagrans had the highest sensitivity to nine tested drugs, except for ketoconazole.