Ghomrassi Hamdi, ben Braiek Olfa, Choiset Yvan, Haertlé Thomas, Hani Khaled, Chobert Jean-Marc, Ghrairi Taoufik
UR12-ES03, University of Sousse, Tunisia.
Dis Aquat Organ. 2016 Feb 11;118(1):31-43. doi: 10.3354/dao02953.
Use of lactic acid bacteria (LAB) as probiotics may provide an alternative to the use of antibiotics in aquaculture. LAB strains isolated from wild fish viscera and skin were evaluated for bacteriocin production and safety aspects (lack of antibiotic resistance, production of virulence factors). 16S rRNA gene sequences revealed the presence of Enterococcus faecium (13 isolates) and Lactococcus lactis (3 isolates) from fish samples. Pulsed-field gel electrophoresis analyses of the 13 enterococci isolates showed that they were all clustered, with greater than 95% similarity. However, RAPD analysis revealed significant molecular diversity between enterococci strains. Six enterococci strains were chosen and evaluated for their antibacterial activities. These strains produced a bacteriocin-like substance and exhibited a broad spectrum of inhibition against pathogenic bacteria isolated from diseased fish, including Streptococcus parauberis, Vagococcus spp., and Carnobacterium maltaromaticum, and in particular against the Gram-negative bacteria Flavobacterium frigidarium, Vibrio pectenicida, V. penaeicida, and Photobacterium damselae. The inhibition activity towards bacterial indicator strains was at a maximum when bacteria were grown at 37°C. However, bacteriocin production was observed at 15°C after 12 h of incubation. Only structural genes of enterocins A and B were detected by PCR in the 6 enterococci strains, suggesting the production of these enterocins. In addition, these strains did not harbor any virulence factors or any significant antibiotic resistance, and they tolerated bile. Our results suggest that enterococci are an important part of the bacterial flora of fish and that some strains have the potential to be used as probiotics.
使用乳酸菌（LAB）作为益生菌可能为水产养殖中抗生素的使用提供一种替代方案。对从野生鱼类内脏和皮肤中分离出的LAB菌株进行了细菌素生产和安全性方面（缺乏抗生素抗性、毒力因子的产生）的评估。16S rRNA基因序列显示，从鱼类样本中分离出了粪肠球菌（13株分离株）和乳酸乳球菌（3株分离株）。对13株肠球菌分离株进行的脉冲场凝胶电泳分析表明，它们都聚集在一起，相似度大于95%。然而，RAPD分析显示肠球菌菌株之间存在显著的分子多样性。选择了6株肠球菌菌株并评估其抗菌活性。这些菌株产生了一种类细菌素物质，对从患病鱼类中分离出的病原菌表现出广泛的抑制作用，包括副乳房链球菌、漫游球菌属和麦芽香肉杆菌，尤其对革兰氏阴性菌弗氏黄杆菌、栉孔扇贝弧菌、对虾弧菌和美人鱼发光杆菌有抑制作用。当细菌在37°C下生长时，对指示菌株的抑制活性最大。然而，在15°C下培养12小时后观察到细菌素的产生。通过PCR在6株肠球菌菌株中仅检测到肠球菌素A和B的结构基因，表明产生了这些肠球菌素。此外，这些菌株不携带任何毒力因子或任何显著的抗生素抗性，并且它们能耐受胆汁。我们的结果表明，肠球菌是鱼类细菌群落的重要组成部分，并且一些菌株有潜力用作益生菌。
