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Antiparasitic efficacy of natamycin isolated from Streptomyces gilvosporeu AXY-25 against Ichthyophthirius multifiliis

Yao, Jia-Yun, Guo, Jian-Lin, Zang, Cheng-Sai, Mi, Guo-Qiang, Jia, Yong-Yi, Yin, Wen-Lin, Cao, Zheng, Xia, Yan-Chun, Pan, Xiao-Yi, Ling, Ling-Yun, Wang, Chun-Feng, Gu, Zhi-Min, Shen, Jin-Yu
Aquaculture 2019 v.506 pp. 465-469
Ichthyophthirius multifiliis, Streptomyces, active ingredients, acute toxicity, antiparasitic agents, bioactive compounds, carbon, chemical structure, hybrids, lethal concentration 50, median effective concentration, natamycin, nuclear magnetic resonance spectroscopy, reproduction, secondary metabolites, spectral analysis, stable isotopes, survival rate
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.