Probiotics when applied in complex evolving (micro-)ecosystems, might be selectively beneficial or detrimental to pathogens when their prophylactic efficacies are prone to ambient interactions. Here, we document a counter-intuitive phenomenon that probiotic-treated zebrafish (Danio rerio) were respectively healthy at higher but succumbed at lower level of challenge with a pathogenic Vibrio isolate. This was confirmed by prominent dissimilarities in fish survival and histology. Based upon the profiling of the zebrafish microbiome, and the probiotic and the pathogen shared gene orthogroups (genetic niche overlaps in genomes), this consequently might have modified the probiotic metabolome as well as the virulence of the pathogen. Although it did not reshuffle the architecture of the commensal microbiome of the vertebrate host, it might have altered the probiotic-pathogen inter-genus and intra-species communications. Such in-depth analyses are needed to avoid counteractive phenomena of probiotics and to optimise their efficacies to magnify human and animal well-being. Moreover, such studies will be valuable to improve the relevant guidelines published by organisations such as FAO, OIE and WHO.

当益生菌应用于复杂的进化（微）生态系统时，当它们的预防功效易于与环境相互作用时，它们可能对病原体有选择性地有益或有害。在这里，我们记录了一个违反直觉的现象，即益生菌处理的斑马鱼（Danio rerio）分别在较高水平时健康，但在较低水平的致病性弧菌攻击下死亡隔离。鱼类存活率和组织学的显着差异证实了这一点。根据斑马鱼微生物组的分析，以及益生菌和病原体共享基因组（基因组中的遗传生态位重叠），这因此可能改变了益生菌代谢组以及病原体的毒力。虽然它没有重新调整脊椎动物宿主共生微生物组的结构，但它可能已经改变了益生菌-病原体的属间和种内通讯。需要进行这种深入的分析，以避免益生菌的反作用现象，并优化其功效以扩大人类和动物的福祉。此外，此类研究对于改进粮农组织、世界动物卫生组织和世卫组织等组织发布的相关准则也很有价值。