Seroepidemiological studies on domestic animal and human diseases infected with enterohemorrhagic Escherichia coli.

为了解某种牛场产志贺毒素大肠埃希菌(STEC)感染犊牛的情况，采用聚合酶链式反应技术对S产志贺毒素基因进行检测。2月龄以下小牛、2~8月龄黄牛和1岁以上成年牛的患病率分别为39.4%、79%和40.8%。不同品种(荷斯坦牛、日本黑牛、F1：HxB)小牛粪便标本中STEC的检出频率无明显差异。用酶联免疫吸附试验(EL ISA)检测了奶牛和新生牛初乳和血清中的抗体效价。结果表明，奶牛分娩后即刻初乳中STEC抗体效价最高。…后4-9小时首次食用高抗体滴度初乳可提高初生犊牛血清抗体效价多产，这表明初乳(和奶牛血清)中的抗体效价与新生牛犊之间存在相关性。从这一结果可以看出，新生儿对STEC感染的被动免疫是通过初乳发生的。我们评估了促炎细胞因子如干扰素-γ或肿瘤坏死因子-α介导STX1或STX2致死的可能性。所有小鼠在注射400 ng STX1后3-4天内全部死亡，其致死剂量比STX1低40倍。给小鼠注射STX_1400 ng或StX_2 10 ng后1~6h，小鼠血清和脾组织中均未观察到干扰素-γ和肿瘤坏死因子-α的产生。然而，与C57BL/6小鼠相比，注射133 ng STX_1或3.3 ng STX_2后，干扰素-γ缺陷小鼠和肿瘤坏死因子-α缺陷小鼠显著存活，提示未检测到的干扰素-γ和肿瘤坏死因子-α都参与了STX的致死。本研究利用细胞因子基因敲除小鼠直接证明干扰素-γ和肿瘤坏死因子-α都参与了stx1和stx2的致死。较少

To investigate the frequency of Shiga toxin-producing Escherichia coli (STEC) infected calves at a breeding farm, the plymerase chain reaction (PCR) was used for detection of genes for Shiga toxin (s). The prevalence rates in calves less than 2 months of age, cattle 2-8 months age, and adults greater than 1 year of age were 39.4, 79, and 40.8%, respectively. Detection frequency of STEC in the fecal specimens from calves aged 0-8 months was not different among the breeds of cattle (Holstein, Japanese black cattle, F1 : HxB).Passive immunity against STEC from cows to newborn calves through colostrum was studied. Antibody titers in colostrum and sera from cows and newborn calves were determined by enzyme-linked immunosorbent assay (ELISA). The obtained results indicate that antibody titer to STEC in colostrum from cows soon after parturition was the highest one. The first consumption of colostrum with high antibody titer elevated serum antibody titer from newborn calves at 4-9 hours after … More birth, suggesting a correlation between antibody titer in colostrum (and sera of cows) and newborn calves. From this result, passive immunity to STEC infection is found to be occurred in newborn claves through colostrum. Suggests a new way to protect newborn calves against STEC infection.We assess that possibility of proinflammatory cytokines such as gamma interferon (IFN-γ) or tumor necrosis factor-alpha (TNF-α) mediate lethality of Stx1 or Stx2. All of mice died within 3 to 4 days after injection with 400 ng of Stx1, a lethal dose of Stx2 was lower 40-times than that of Stx1. When mice were given 400 ng of Stx1 or 10 ng of Stx2, IFN-γand TNF-α production in the sera and spleens was not observed 1 h to 6 h after injection. However, when mice were injected with 133 ng of Stx1 or 3.3 ng of Stx2, IFN-γ -deficient mice and TNF-α-deficient mice significantly survived, compared with C57BL/6 mice, suggesting that undetectable levels of both IFN-γ and TNF-α are involved in lethality of Stx. The present study using cytokine-gene knockout mice directly demonstrated that both IFN-γ and TNF-α are involved in lethality of Stx1 and Stx2. Less