In vitro susceptibility of nematophagous fungi to antiparasitic drugs: interactions and implications for biological control

Abstract

The fast anthelmintic resistance development has shown a limited efficiency in the control of animal's endoparasitosis and has promoted research using alternative control methods. The use of chemicals in animal anthelmintic treatment, in association with nematophagous fungi used for biological control, is a strategy that has proven to be effective in reducing the nematode population density in farm animals. This study aims to verify the in vitro susceptibility of the nematophagous fungi Arthrobotrys oligospora, Duddingtonia flagrans and Paecilomyces lilacinus against the antiparasitic drugs albendazole, thiabendazole, ivermectin, levamisole and closantel by using the Minimum Inhibitory Concentration (MIC). MICs ranged between 4.0 and 0.031 µg/mL for albendazole, thiabendazole and ivermectin, between 0.937 and 0.117 µg/mL for levamisole, and between 0.625 and 0.034 µg/mL for closantel. The results showed that all antiparasitic drugs had an in vitro inhibitory effect on nematophagous fungi, which could compromise their action as agents of biological control. D. flagrans was the most susceptible species to all drugs.Keywords: nematophagous fungi, benzimidazoles, ivermectin, levamisole, closantel. Suscetibilidade in vitro de fungos nematófagos à antiparasitários: interações e implicações para o controle biológicoResumo O desenvolvimento rápido da resistência anti-helmíntica demonstrou a eficiência limitada no controle de endoparasitoses em animais, e promoveu a investigação em métodos de controles alternativos. O uso de produtos químicos no tratamento anti-helmíntico animal, em associação com fungos nematófagos utilizados para o controlo biológico, é uma estratégia que tem provado ser eficaz na redução da densidade da população de nematódeos em animais agrícolas. Este estudo teve como objetivo verificar a suscetibilidade in vitro dos fungos nematófagos Arthrobotrys oligospora, Duddingtonia flagrans e Paecilomyces lilacinus frente aos antiparasitários albendazol, tiabendazol, ivermectina, levamisol e closantel, usando a concentração inibitória mínima (MIC). Os MICs variaram entre 4,0 e 0,031 μg/mL para albendazol, tiabendazol e ivermectina, entre 0,937 e 0,117 μg/mL para o levamisol, e entre 0,625 e 0,034 μg/mL para closantel. Os resultados mostraram que todos os antiparasitários tiveram um efeito inibidor in vitro sobre os fungos nematófagos, o que poderia comprometer suas atividades como agentes de controle biológico. D. flagrans foi a espécie mais sensível a todas as drogas.Palavras-chave: fungos nematófagos, benzimidazóis, ivermectina, levamisol, closantel.

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

“…In vivo assays performed in sheep and buffaloes showed that the activity of D. flagrans chlamydospores is inhibited when used in combination with albendazole, and the fungus is rarely recovered from fecal culture after 48 h following a single dose of albendazole (Sanyal et al 2004). Vieira et al (2017) demonstrated that the minimal inhibitory concentration (MIC) of albendazole against the hyphal growth of D. flagrans is 0Á03 μg ml −1 , which is lower than the EC 50 value of fenbendazole against the spore germination of D. flagrans in this study. In vitro growth assays performed by Singh et al (2010) revealed that albendazole exerts inhibitory effects on two egg-parasitic fungi, Verticillian chlamydosporium and Paecilomyces lilacinus, but V. chlamydosporium is more sensitive to albendazole than P. lilacinus.…”

“…Triclabendazole is a widely used benzimidazole fungicide, and it exclusively prevents and cures the diseases caused by Fasciola gigantica and Fasciola hepatica. Regarding an in vitro growth experiment performed by using the microdilution technique, the MIC of triclabendazole against D. flagrans was reported to be 0Á062 μg ml −1 (Vieira et al 2017). This study indicated that EC 50 of triclabendazole against the chlamydospore germination of D. flagrans is 1Á2 μg ml −1 .…”

“…Ivermectin is widely used in the control of nematode and ectoparasitic diseases in livestock because of its high efficiency and broad spectrum. Vieira et al (2017) reported that the MIC of ivermectin against D. flagrans in vitro is 0Á117 μg ml −1 . Differences were noted between this study and the above research results.…”

“…The compatibility of nematophagous fungi with albendazole was analyzed in the biological control of animal parasites (Sanyal et al 2004;Singh et al 2010). Another study reported the in vitro susceptibility of nematophagous fungi A. oligospora, D. flagrans and P. lilacinus to albendazole, thiabendazole and closantel (Vieira et al 2017).…”

Combined use of chemical and biological compounds to control hookworm

“…Vieira et al . (2017) mentioned that antiparasitic compounds have an in vitro inhibitory effect on nematophagous fungi, compromising their activity as biological control agents – something that can be observed in group G7.…”