陰道鞭毛蟲（Trichomonas vaginalis, T. vaginalis）是一種具有四條鞭毛與一條波動膜的真核生物，是最常見的非病毒性性傳播感染，每年感染人數約為 2.76 億。T. vaginalis 寄生於陰道內，而陰道環境中包含多種細菌，以乳酸桿菌（Lactobacillus）為優勢菌種，次為比菲德氏菌（Bifidobacterium）。先前研究指出，與 T. vaginalis 共感染的病患中，短雙歧桿菌（Bifidobacterium breve）的數量會下降。然而，T. vaginalis 與 B. breve 間的關係仍尚未明朗。因此，我們旨在探討 T. vaginalis 與益生菌 B. breve 之間的交互作用。在共培養 4 小時後，我們觀察到 T. vaginalis 的數量顯著增加，而 B. breve 則相較對照組明顯減少。此外，我們也觀察到 B. breve 圍繞在 T. vaginalis 的表面，顯示雙方之間確實存在實體交互作用。接著，我們利用次世代定序（NGS）技術進行轉錄體分析，以探討 T. vaginalis 與 B. breve 共培養後的基因表現變化。結果顯示，與脂肪酸代謝與DNA 複製相關的基因顯著上調。進一步的代謝體分析也證實，B. breve 改變了 T. vaginalis 中長鏈脂肪酸的含量。此外，我們確認了 T. vaginalis 的致病因子表現，尤其是黏附素蛋白（adhesin）表現有上升的趨勢。接著，我們將經 B. breve 共培養後的 T. vaginalis 移轉至 HeLa 細胞中，並測試其誘導的發炎細胞激素產生情形。結果顯示，B. breve 並未改變 T. vaginalis 所誘導的 IL-6 與 IL-8 的表現。此外，我們也發現，B. breve 的預處理無法顯著減少 HeLa 細胞受到 T. vaginalis 感染後的細胞病變效應，亦即 B. breve 並不會改變 T. vaginalis 與 HeLa 細胞之間的交互作用。綜合而言，我們觀察到 B. breve 能促進 T. vaginalis 的生長並改變其基因表現，特別是在脂肪酸代謝方面。此外，我們的研究結果也暗示，作為益生菌的 B. breve 在 T. vaginalis 感染期間，可能扮演的是社區保護(community-protecting)角色，而非直接的保護宿主角色。然而，此一假說仍有待進一步研究驗證。

Trichomonas vaginalis is a eukaryotic organism with four flagella and one undulating membrane. It is the most common non-viral sexually transmitted infection, with 276 million cases annually. T. vaginalis parasitizes the vagina, where the environment consists of various bacteria, with Lactobacillus as the dominant species, followed by Bifidobacterium. Previous studies have shown that Bifidobacterium breve decreased in patients co-infected with T. vaginalis. However, the relationship between T. vaginalis and B. breve remains poorly understood. Therefore, we aimed to uncover the interaction between T. vaginalis and the probiotic B. breve. After 4 hours of co-culture, the number of T. vaginalis significantly increased, while B. breve decreased compared to the control. Additionally, we observed that B. breve surrounded the surface of T. vaginalis during co-culture, emphasizing the actual interaction of the two characters. Next-generation sequencing (NGS)-based transcriptomics analysis was performed to profile the gene expression changes in T. vaginalis after co-culturing with B. breve. The NGS results showed that genes associated with fatty acid metabolism and DNA replication were significantly upregulated. Based on the metabolomics analysis, we confirmed that B. breve altered the contents of long-chain fatty acids in T. vaginalis. Additionally, we confirmed the expression of virulence factors in T. vaginalis; the adhesin protein showed an upregulated trend. Next, we transferred T. vaginalis, which had been co-cultured with B. breve, to HeLa cells and tested the production of inflammatory cytokines. The results showed that B. breve did not change the levels of T. vaginalis-induced IL-6 and IL-8. Conversely, we found that the pre-treatment of B. breve did not significantly reduce cytopathic effects in HeLa cells subsequently infected with T. vaginalis. We also found that B. breve does not alter the interaction between T. vaginalis and HeLa cells. In conclusion, we observed that B. breve enhanced the growth and altered the gene expression in T. vaginalis, especially fatty acid metabolism. In addition, our findings implied that, as a probiotic, B. breve might play a community-protecting role rather a protective role during T. vaginalis infection, although this hypothesis needs further investigation.

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