Probiotics such as various strains of Lactobacillaceae have been shown to have antimicrobial and immunomodulatory activity. In vitro studies have shown that Lactobacilli can decrease bacterial biofilm formation. Effects on immune cells have been unclear with most studies showing anti-inflammatory activity. The mechanism of effects has not been clearly elucidated. In these studies, we used different concentrations of live Lactobacillus acidophilus as well as cell free filtrate (CFF) derived from different concentrations of bacteria. Use of CFF is advantageous as a therapeutic because in vivo it can directly contact immune cells and its concentration is fixed. Both live cells and CFF inhibited Pseudomonas aeruginosa biofilm formation. Importantly, we show that high concentration CFF destroyed mature biofilm. This activity was not due to a lowered pH per se, as pH matched HCl did not remove mature biofilm. High concentration CFF totally inhibited P. aeruginosa growth and was bactericidal (>99.99%), but low concentration CFF was not bactericidal. To examine the immunomodulatory effects of L. acidophilus, we incubated THP-1 monocytes and derived macrophages with CFF and measured TNFα production. CFF did not significantly increase TNFα production in THP-1 monocytes. When cells were prestimulated with LPS, high concentration CFF increased TNFα production even further. In macrophages, high concentration CFF alone increased TNFα production but did not affect LPS prestimulated cells. In contrast, low concentration CFF decreased TNFα production in LPS prestimulated cells. To elucidate the possible mechanisms for these effects, we repeated the experiments using a NF-κB reporter THP-1 cell line. High concentration CFF increased NF-κB activity in monocytes and macrophages. In LPS prestimulated macrophages, only low concentration CFF reduced NF-κB activity. These results suggest that high concentration CFF alone induced NF-κB expression which could account partially for an increase in TNFα production. On the other hand, in macrophages, the lower non-bactericidal concentration of CFF reduced NF-κB expression and decreased TNFα production after LPS prestimulation. Taken together, the results provide evidence that different concentrations of L. acidophilus CFF possess varying bactericidal, anti-biofilm and immunomodulatory effects. This is important in vivo to evaluate the possible use of L. acidophilus CFF in different conditions.

益生菌，如各种菌株乳酸杆菌科已被证明具有抗微生物和免疫调节活性。体外研究表明，乳酸杆菌可以减少细菌生物膜的形成。大多数研究显示抗炎活性，对免疫细胞的影响尚不清楚。作用机制尚未清楚阐明。在这些研究中，我们使用不同浓度的活嗜酸乳杆菌以及来自不同浓度细菌的无细胞滤液 (CFF)。使用 CFF 作为治疗剂是有利的，因为体内可直接接触免疫细胞，浓度固定。活细胞和 CFF 均受到抑制铜绿假单胞菌生物膜的形成。重要的是，我们表明高浓度 CFF 破坏了成熟的生物膜。这种活动不是由于降低的 pH 值本身，因为与 pH 值匹配的 HCl 不会去除成熟的生物膜。高浓度 CFF 完全抑制铜绿假单胞菌生长和杀菌（>99.99%），但低浓度 CFF 不杀菌。检查免疫调节作用嗜酸乳杆菌，我们用 CFF 培养 THP-1 单核细胞和衍生的巨噬细胞并测量 TNFα 的产生。CFF 没有显着增加 THP-1 单核细胞中 TNFα 的产生。当用 LPS 预刺激细胞时，高浓度 CFF 会进一步增加 TNFα 的产生。在巨噬细胞中，单独的高浓度 CFF 会增加 TNFα 的产生，但不会影响 LPS 预刺激的细胞。相反，低浓度 CFF 降低了 LPS 预刺激细胞中 TNFα 的产生。为了阐明这些影响的可能机制，我们使用 NF-κB 报告基因 THP-1 细胞系重复了实验。高浓度 CFF 增加了单核细胞和巨噬细胞中的 NF-κB 活性。在 LPS 预刺激的巨噬细胞中，只有低浓度的 CFF 会降低 NF-κB 活性。这些结果表明，单独的高浓度 CFF 诱导 NF-κB 表达，这可能部分解释了 TNFα 产生的增加。另一方面，在巨噬细胞中，CFF 的较低非杀菌浓度降低了 NF-κB 的表达，并在 LPS 预刺激后降低了 TNFα 的产生。总之，这些结果提供了证据表明不同浓度的嗜酸乳杆菌CFF 具有不同的杀菌、抗生物膜和免疫调节作用。这个很重要体内评估可能的用途嗜酸乳杆菌不同条件下的 CFF。