Flavobacterium psychrophilum produces biofilms under laboratory conditions, and it has been inconclusively suggested that F. psychrophilum biofilms can be a potential reservoir for transmission of the pathogen to a fish population under fish farming conditions. Therefore, there is a need for anti-biofilm compounds. The main aim of this study was to determine the anti-biofilm properties of certain compounds and bacteriophages on F. psychrophilum biofilms under static conditions using a standard 96-well microtiter plate biofilm assay in vitro. Eight compounds (A-type proanthocyanidins, D-leucine, EDTA, emodin, fucoidan, L-alliin, parthenolide, and 2-aminoimidazole) at three sub-minimum inhibitory concentrations (sub-MICs), four bacteriophages (Fpv-3, Fpv-9, Fpv-10, and Fpv-21), and a phage combination (Fpv-9 + Fpv-10) were tested for inhibition of biofilm formation and reduction of the biomass of mature biofilms formed by two smooth isolates (P7-9/10 and P1-10B/10) and two rough isolates (P7-9/2R/10 and P1-10B/2R/10) of F. psychrophilum. The crystal violet staining method was used to stain the biofilms. Most of the compounds at sub-MICs inhibited the biofilm formation of mainly smooth isolates, attaining up to 80% inhibition. Additionally, the same reduction trend was also observed for 2-aminoimidazole, emodin, parthenolide, and D-leucine on the biomass of mature biofilms in a concentration-dependent manner. The anti-biofilm properties of the compounds are believed to lie in their ability to disturb the cellular interactions during biofilm formation and probably to cause cell dispersal in already formed biofilms. Lytic bacteriophages efficiently inhibited biofilm formation of F. psychrophilum, while they partially reduced the biomass of mature biofilms. However, the phage combination (Fpv-9 + Fpv-10) showed a successful reduction in the biomass of F. psychrophilum mature biofilms. We conclude that inhibiting compounds together with bacteriophages may supplement the use of disinfectants against bacterial biofilms (e.g., F. psychrophilum biofilms), leading to a reduced occurrence of bacterial coldwater disease outbreaks at fish farms.

中文翻译：

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化合物和噬菌体对体外嗜冷黄杆菌生物膜的抑制活性

Flavobacterium psychrophilum 在实验室条件下产生生物膜，并且已经不确定地表明 F. psychrophilum 生物膜可能是在鱼类养殖条件下将病原体传播到鱼类种群的潜在储存库。因此，需要抗生物膜化合物。本研究的主要目的是在静态条件下使用标准的 96 孔微量滴定板生物膜测定法确定某些化合物和噬菌体对 F. psychrophilum 生物膜的抗生物膜特性。八种化合物（A 型原花青素、D-亮氨酸、EDTA、大黄素、岩藻多糖、L-蒜氨酸、小白菊内酯和 2-氨基咪唑），三种亚最低抑制浓度（亚 MIC），四种噬菌体（Fpv-3、Fpv -9、Fpv-10 和 Fpv-21)、和噬菌体组合 (Fpv-9 + Fpv-10) 被测试抑制生物膜形成和减少由两个平滑分离物 (P7-9/10 和 P1-10B/10) 和两个粗糙分离物形成的成熟生物膜的生物量(P7-9/2R/10 和 P1-10B/2R/10) F. psychrophilum。结晶紫染色法用于染色生物膜。大多数亚 MIC 的化合物抑制主要是光滑分离株的生物膜形成，抑制率高达 80%。此外，还观察到 2-氨基咪唑、大黄素、小白菊内酯和 D-亮氨酸对成熟生物膜生物量的浓度依赖性降低趋势。据信，这些化合物的抗生物膜特性在于它们能够在生物膜形成过程中干扰细胞相互作用，并可能导致细胞扩散到已形成的生物膜中。溶菌噬菌体有效地抑制了嗜冷嗜热菌的生物膜形成，同时它们部分地减少了成熟生物膜的生物量。然而，噬菌体组合 (Fpv-9 + Fpv-10) 显示成功减少 F. psychrophilum 成熟生物膜的生物量。我们得出结论，抑制化合物和噬菌体可以补充使用消毒剂对抗细菌生物膜（例如嗜冷嗜热菌生物膜），从而减少养鱼场细菌性冷水病爆发的发生率。