Antiparasitic efficacy of natamycin isolated from Streptomyces gilvosporeu AXY-25 against Ichthyophthirius multifiliis
2019
Yao, Jia-Yun | Guo, Jian-Lin | Zang, Cheng-Sai | Mi, Guo-Qiang | Jia, Yong-Yi | Yin, Wenlin | Cao, Zheng | Xia, Yan-Chun | Pan, Xiao-Yi | Ling, Ling-Yun | Wang, Junfeng | Gu, Zhi-Min | Shen, Jin-Yu
The main purpose of the present study was undertaken to isolate bioactive substances from microbial secondary metabolites of Streptomyces gilvosporeu AXY-25 and to determine their antiparasitic effect against Ichthyophthirius multifiliis. A pure compound showing strong anti- I. multifiliis activity was isolated from a culture of S. gilvosporeu AXY-25 by using the method of bioassay-guided isolation. The chemical structure of the active compound was confirmed as natamycin (NAT) by spectral analysis (EI-MS, ¹H NMR and ¹³C NMR). An in vitro anti-parasitic assay demonstrated that 100% of theronts were killed with a concentration of 25.0 mg L⁻¹ NAT for 4 h with an effective concentration (EC₅₀) (95% CI) at 10.9 (10.7–11.1) mg L⁻¹. Similiary, all tomonts were killed by a dose of 25.0 mg L⁻¹. An in vivo anti-parasitic assay showed that the number of I. multifiliis trophonts on the surface of hybrid Erythroculter ilishaeformis in the NAT-treated group were markedly lower when compared to the control group (p < 0.05). Mortality in the 25.0 mg L⁻¹ NAT-treated group was 36.7% at day 10. Mortality in the control group due to the I. multifiliis infection was 83.3% by day 10. In addition, the survival rate and reproduction of tomonts in the 25.0 mg L⁻¹NAT treated group were markedly lower than those in the control group (p < 0.05). The results of the acute toxicity of NAT indicated that NAT was safe to use on hybrid E. ilishaeformis, the median lethal concentration (LC₅₀) was 508.6 mg L⁻¹.
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