Ohkusa T, Okayasu I, Ogihara T, Morita K, Ogawa M, Sato N
Department of Gastroenterology, Juntendo University, School of Medicine, Tokyo, Japan.
Gut. 2003 Jan;52(1):79-83. doi: 10.1136/gut.52.1.79.
Bacteria are implicated in certain forms of model chronic colitis but the identity and role of bacteria in human ulcerative colitis (UC) are uncertain.
To isolate pathogenic bacteria from inflamed mucosa of patients with UC, to examine whether the bacteria have a toxin to Vero cells, and to determine whether the toxin induces UC-like lesions in animals.
Bacteria were isolated from UC patients and supernatants from cultures were filtered and tested for cytotoxicity to Vero cells. Bacterial cells producing the cytotoxic supernatants were examined by polymerase chain reaction for verotoxin genes. Culture supernatants of cytotoxic strains were examined by high performance liquid chromatography for organic acid concentrations. Mice were given enemas containing organic acid at the mean concentration in the supernatants of cytotoxic strains to ascertain whether colonic lesions appear in UC.
Only supernatants from cultures of Fusobacterium varium killed Vero cells. Bacterial cells lacked verotoxin genes. Bacterial culture supernatants contained high concentrations of n-butyric acid and the mean concentration (32 mmol/l) was cytotoxic to Vero cells. Twenty four hours after mice were given enemas containing either butyric acid or F varium culture supernatants, colonic ulcers with crypt abscesses, inflammatory cell infiltration, and apoptotic changes were observed.
Butyric acid in culture supernatants from cultures of F varium caused UC-like lesions in mice. This study indicates that F varium may be one of the elusive pathogenic factors in UC.
细菌与某些形式的模型性慢性结肠炎有关，但细菌在人类溃疡性结肠炎（UC）中的身份和作用尚不确定。
从UC患者的炎症黏膜中分离致病细菌，检测这些细菌是否对Vero细胞有毒素，并确定该毒素是否能在动物体内诱导出UC样病变。
从UC患者中分离细菌，将培养物的上清液过滤并检测其对Vero细胞的细胞毒性。通过聚合酶链反应检测产生细胞毒性上清液的细菌细胞是否含有志贺毒素基因。采用高效液相色谱法检测细胞毒性菌株培养上清液中的有机酸浓度。给小鼠灌肠含有细胞毒性菌株上清液中平均浓度的有机酸，以确定UC中是否会出现结肠病变。
只有多变梭杆菌培养物的上清液能杀死Vero细胞。细菌细胞缺乏志贺毒素基因。细菌培养上清液中含有高浓度的正丁酸，其平均浓度（32 mmol/L）对Vero细胞具有细胞毒性。给小鼠灌肠含有丁酸或多变梭杆菌培养上清液24小时后，观察到有隐窝脓肿、炎性细胞浸润和凋亡改变的结肠溃疡。
多变梭杆菌培养上清液中的丁酸可在小鼠中引起UC样病变。本研究表明，多变梭杆菌可能是UC中难以捉摸的致病因素之一。
