title: Anti-parasitic activities of specific bacterial extracellular products  of Streptomyces griseus SDX-4 against Ichthyophthirius multifiliis.
abstract: The ciliate Ichthyophthirius multifiliis is one of the most pathogenic parasites of fish maintained in captivity. In this study, effects of bacterial extracellular products of Streptomyces griseus SDX-4 against I. multifiliis were determined. The fermentation liquor of S. griseus was extracted successively in a separating funnel with petroleum ether, ethyl acetate, and n-butanol. In vitro assays revealed that the n-butanol extracts (NBu-E) and ethyl acetate extracts (Eto-E) of S. griseus were observed to be more effective against theronts than the other extracts with median effective concentration (EC50) values of 0.86 and 12.5 mg L(-1), respectively, and significantly reduced the survival of the tomonts and the total number of theronts released by the tomonts (P<0.05). All encysted tomonts were killed when the concentration of NBu-E was 30.0 mg L(-1). Results of in vivo test demonstrated that the number of I. multifiliis trophonts on the grass carp treated with NBu-E was markedly lower compared to the control group at 11 days after exposed to theronts (P<0.05). In the control group, 100% mortality was observed owing to heavy I. multifiliis infection at 11 days after the exposure. On the other hand, only 9.5% mortality owing to parasite infection was recorded in the groups treated with the NBu-E (30 mg L(-1)). The median lethal dose (LD50) of NBu-E for grass carp was 152.4 mg L(-1). Our results indicate that n-butanol extract of S. griseus will be useful in aquaculture for controlling I. multifiliis infections.
authors.forename: Jia-Yun
authors.initials: JY
authors.lastname: Yao
authors.forename: Wen-Lin
authors.initials: WL
authors.lastname: Yin
authors.forename: Xin-Cang
authors.initials: XC
authors.lastname: Li
authors.forename: Gang
authors.initials: G
authors.lastname: Li
authors.forename: Yang
authors.initials: Y
authors.lastname: Xu
authors.forename: Wei-Ming
authors.initials: WM
authors.lastname: Ai
authors.forename: Jin-Yu
authors.initials: JY
authors.lastname: Shen
mesh_terms: D000818:Animals; D002347:Carps / Q000469:parasitology*; D016770:Ciliophora Infections / Q000188:drug therapy / Q000662:veterinary*; D005393:Fish Diseases / Q000188:drug therapy*; D016803:Hymenostomatida / Q000187:drug effects*; D007928:Lethal Dose 50; D013305:Streptomyces griseus / Q000737:chemistry* / Q000145:classification