Citrobacter braakii (C. braakii) is an anaerobic, gram-negative bacterium that has been isolated from the environment, food, and humans. Infection by C. braakii has been associated with acute mucosal inflammation in the intestine, respiratory tract, and urinary tract. However, the pathogenesis of C. braakii in the gastric mucosa has not yet been clarified. In this study, the bacterium was detected in 35.5% (61/172) of patients with chronic gastritis (CG) and was closely associated with the severity of mucosal inflammation. Citrobacter braakii P1 isolated from a patient with CG exhibited urease activity and acid resistance. It contained multiple secretion systems, including a complete type I secretion system (T1SS), T5aSS and T6SS. We then predicted the potential pilus-related adhesins. Citrobacter braakii P1 diffusely adhered to AGS cells and significantly increased lactate dehydrogenase (LDH) release; the adhesion rate and LDH release were much lower in HEp-2 cells. Strain P1 also induced markedly increased mRNA and protein expression of IL-8 and TNF-α in AGS cells, and the fold increase was much higher than that in HEp-2 cells. Our results demonstrate proinflammatory and cytotoxic role of C. braakii in gastric epithelial cells, indicating the bacterium is potentially involved in inducing gastric mucosa inflammation.

中文翻译：

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从人胃中分离出的细胞毒性布氏柠檬酸杆菌的表征

布氏柠檬酸杆菌( C. braakii ) 是一种厌氧革兰氏阴性细菌，已从环境、食物和人类中分离出来。布氏梭菌感染与肠道、呼吸道和泌尿道的急性粘膜炎症有关。然而，布氏衣原体在胃粘膜中的发病机制尚未阐明。在这项研究中，35.5%（61/172）的慢性胃炎（CG）患者中检测到该细菌，并且与粘膜炎症的严重程度密切相关。从 CG 患者中分离出的布氏柠檬酸杆菌P1 表现出脲酶活性和耐酸性。它包含多个分泌系统，包括完整的I型分泌系统（T1SS）、T5aSS和T6SS。然后我们预测了潜在的菌毛相关粘附素。布氏柠檬酸杆菌P1 广泛粘附于 AGS 细胞并显着增加乳酸脱氢酶 (LDH) 的释放；HEp-2 细胞中的粘附率和 LDH 释放要低得多。P1菌株还诱导AGS细胞中IL-8和TNF-α的mRNA和蛋白表达显着增加，且增加倍数远高于HEp-2细胞。我们的结果证明了布氏梭菌在胃上皮细胞中的促炎和细胞毒作用，表明该细菌可能参与诱导胃粘膜炎症。