导读：日本研究人员在新一期英国《科学报道》杂志网络版上报告说，他们调查发现，感染一种可导致蛀牙的变形链球菌后，患上溃疡性大肠炎的风险将是正常情况的4倍以上。
溃疡性大肠炎是一种大肠炎症性疾病，会反复出现腹泻及便血。溃疡性大肠炎被认为与免疫功能异常有关，但是一直不清楚具体机制。
大阪大学等机构研究人员组成的一个研究小组介绍说，他们首先将一种特定类型的变形链球菌注射到患有轻度肠炎的小鼠体内。结果小鼠肠炎恶化，生存率从注射之前的70%骤降至20%。研究人员调查发现，小鼠的肝脏受到这种菌的影响，产生了与炎症有关的物质。研究小组认为这是导致免疫异常的导火索。
研究小组又调查了98名溃疡性大肠炎患者。结果发现，其中有56人感染了变形链球菌，其中约14%感染的是与实验鼠注射类型相同的变形链球菌。感染这种特定类型的变形链球菌后，溃疡性大肠炎的发病风险是健康人的4.55倍。这一发现可能有助于开发出治疗溃疡性大肠炎的新方法。
不过，如果向小鼠口腔内投放这种链球菌，并没有什么影响，但是即使少量进入血液中，肠炎也会恶化，生存率降低。因此研究小组提醒说，刷牙时应注意避免出血，而已患上溃疡性大肠炎的患者要注意保持口腔卫生，这样可能有助于改善症状。
Infection of specific strains of Streptococcus mutans, oral bacteria, confers a risk of ulcerative colitis
Ayuchi Kojima, Kazuhiko Nakano, Koichiro Wada, Hirokazu Takahashi, Kazufumi Katayama, Masato Yoneda, Takuma Higurashi, Ryota Nomura, Kazuya Hokamura, Yoshinori Muranaka, Nobuyuki Matsuhashi, Kazuo Umemura, Yoshinori Kamisaki, Atsushi Nakajima & Takashi Ooshima
Although oral bacteria-associated systemic diseases have been reported, association between Streptococcus mutans, pathogen of dental caries, and ulcerative colitis (UC) has not been reported. We investigated the effect of various S. mutans strains on dextran sodium sulfate (DSS)-induced mouse colitis. Administration of TW295, the specific strain of S. mutans, caused aggravation of colitis; the standard strain, MT8148 did not. Localization of TW295 in hepatocytes in liver was observed. Increased expression of interferon-γ in liver was also noted, indicating that the liver is target organ for the specific strain of S. mutans-mediated aggravation of colitis. The detection frequency of the specific strains in UC patients was significantly higher than in healthy subjects. Administration of the specific strains of S. mutans isolated from patients caused aggravation of colitis. Infection with highly-virulent specific types of S. mutans might be a potential risk factor in the aggravation of UC.
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