Managing bacterial infections is of great importance in livestock production, particularly those caused by Salmonella enterica serovars Typhimurium or Dublin, which can impact both animal health and performance, as well as human food safety. Direct-fed microbials (DFM) can support gastrointestinal function and alleviate the potential negative effects of bacterial infections. In the present study, the capacity of a multispecies bacterial-based DFM containing Ligilactobacillus (formerly Lactobacillus) animalis 506, Propionibacterium freudenreichii 507, Bacillus licheniformis 809, and B. subtilis 597 to reduce S. Typhimurium ATCC14028 invasion was investigated using a co-incubation model with the HT29-MTX-E12 cell line (Exp. 1). Next, a possible antagonistic effect of the DFM against S. Dublin ATCC 41286 was evaluated using an in vitro agar well diffusion method following a co-incubation of 48 h (Exp. 2). At last, a series of experiments were performed to evaluate how different doses (6.25 × 106, 2.50 × 107, or 1.00 × 108 CFU/well) of the DFM would support the integrity of intestinal epithelial cells challenged or not with S. Typhimurium ATCC14028 or hydrogen peroxide under a transepithelial electrical resistance (TEER) assay with Caco-2 cells (Exp. 3 and 4). In Exp. 1, BDP significantly (P < 0.001) reduced by 90.8% the invasion of S. Typhimurium into HT29-MTX-E12 cells, whereas viability of the potentially harmful bacteria was reduced by 21.0% (P < 0.0001). In Exp. 2, the antagonistic properties of BDP towards S. Dublin were confirmed by the detection of a clear inhibition zone (size = 8.6 mm). Lastly, without challenge, the lowest dose of the DFM (6.25 × 106 CFU) provided the greatest support on the cells (treatment × hour; P < 0.0001). However, when the cells were challenged with S. Typhimurium, all doses alleviated the loss of integrity caused by the pathogen (treatment × hour; P < 0.0001). In cells challenged with hydrogen peroxide, the greater dose (1.00 × 108 CFU) supported the cells for a longer period of time (treatment × hour; P < 0.0001). These in vitro findings set the stage for exploring the potential benefits of using a novel DFM as a promising tool and strategy to mitigate Salmonella enterica infections in ruminants and improve animal health, food safety, and public health. Further in vivo confirmation needs to be developed to validate these preliminary in vitro results.

中文翻译：

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简短的交流：一种基于多物种的细菌直接喂养微生物可减轻沙门氏菌的侵袭并支持体外上皮完整性


管理细菌感染在畜牧生产中非常重要，尤其是那些由鼠伤寒沙门氏菌血清型或都柏林沙门氏菌引起的细菌感染，这会影响动物的健康和生产性能，以及人类的食品安全。直接喂养的微生物 （DFM） 可以支持胃肠道功能并减轻细菌感染的潜在负面影响。在本研究中，含有 Ligilactobacillus（以前称为 Lactobacillus）animalis 506、Propionibacterium freudenreichii 507、Bacillus licheniformis 809 和 B. subtilis 597 的多物种基于细菌的 DFM 减少鼠伤寒沙门氏菌ATCC14028侵袭的能力是使用与 HT29-MTX-E12 细胞系 （Exp. 1） 的共孵育模型研究的。接下来，在共孵育 48 小时 （Exp. 2） 后，使用体外琼脂孔扩散法评估 DFM 对都柏林链球菌 ATCC 41286 的可能拮抗作用。最后，进行了一系列实验，以评估不同剂量 （6.25 × 106、2.50 × 107 或 1.00 × 108 CFU/孔）的 DFM 如何支持肠上皮ATCC14028细胞的完整性在跨上皮电阻 （TEER） 测定下用 Caco-2 细胞 （实验 3 和 4）。在实验 1 中，BDP （P < 0.001） 显着减少了鼠伤寒沙门氏菌对 HT29-MTX-E12 细胞的侵袭 90.8%，而潜在有害细菌的活力降低了 21.0% （P < 0.0001）。在 Exp. 2 中，通过检测明确的抑制区 （尺寸 = 8.6 mm） 来证实 BDP 对 S. Dublin 的拮抗特性。最后，在没有挑战的情况下，最低剂量的 DFM （6.25 × 106 CFU） 为细胞提供了最大的支持（治疗 × 小时;P < 0.0001）. 然而，当细胞受到鼠伤寒沙门氏菌的攻击时，所有剂量都减轻了病原体引起的完整性丧失（治疗 × 小时;P < 0.0001）.在用过氧化氢攻击的细胞中，较大剂量 （1.00 × 108 CFU） 支持细胞更长的时间 （处理 × 小时;P < 0.0001）.这些体外发现为探索使用新型 DFM 作为减轻反刍动物肠道沙门氏菌感染并改善动物健康、食品安全和公共卫生的有前途的工具和策略的潜在好处奠定了基础。需要进一步进行体内确认以验证这些初步体外结果。