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

为了解某养殖场犊牛产滋贺毒素大肠杆菌（STEC）的感染情况，采用聚合酶链反应（PCR）技术检测滋贺毒素基因。小于2月龄的小牛、2-8月龄的牛和大于1岁的成年牛的患病率分别为39.4%、79%和40.8%。从0-8月龄犊牛粪便中检出STEC的频率在不同品种牛（荷斯坦牛、日本黑牛、F1：HxB）中无差异。用酶联免疫吸附试验（ELISA）测定了奶牛和新生小牛初乳和血清中的抗体效价。结果表明，母牛分娩后不久初乳中的STEC抗体效价最高。第一次食用高抗体效价的初乳可提高新生犊牛4-9小时后的血清抗体效价 关于我们 出生，表明初乳（和奶牛血清）和新生小牛的抗体滴度之间的相关性。从这个结果可以看出，新生儿通过初乳对STEC感染产生了被动免疫。我们评估了促炎细胞因子如γ干扰素（IFN-γ）或肿瘤坏死因子-α（TNF-α）介导Stx 1或Stx 2致死性的可能性。400 ng Stx 1注射后3 ~ 4 d内全部死亡，Stx 2的致死量比Stx 1低40倍。当给小鼠注射400 ng Stx 1或10 ng Stx 2时，在注射后1 h至6 h未观察到血清和脾脏中IFN-γ和TNF-α的产生。然而，当小鼠注射133 ng Stx 1或3.3 ng Stx 2时，与C57 BL/6小鼠相比，IFN-γ缺陷型小鼠和TNF-α缺陷型小鼠显著存活，表明检测不到的IFN-γ和TNF-α水平与Stx的致死有关。本研究使用干扰素基因敲除小鼠直接证明IFN-γ和TNF-α都参与了Stx 1和Stx 2的致死性。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