Stevens P, Chu C L, Young L S
Infect Immun. 1980 Sep;29(3):1055-61. doi: 10.1128/iai.29.3.1055-1061.1980.
Eighty percent of blood culture isolates of Escherichia coli K-1 are resistant to in vitro opsonophagocytosis by normal human granulocytes and fresh serum. To determine the basis for susceptibility to phagocytosis in 20% of bacteremic K-1 E. coli, we investigated possible quantitative and qualitative immunochemical differences in the K-1 antigen content among resistant and sensitive isolates. We prepared extracts of blood culture K-1 E. coli by sonication and determined the K-1 polysaccharide content per dry weight of bacteria by rocket immunoelectrophoresis using cross-reactive equine anti-group B meningococcal sera. We assessed qualitative differences in the antigen content by crossed immunoelectrophoresis, using an immune globulin fraction and isolated immunoglobulin G (IgG) and IgM from the group B antisera. Three different resistant K-1 isolates contained a mean K-1 content of 48.5 +/- 7.6 mug/mg +/- standard deviation of dry bacteria, and three sensitive isolates contained 23.2 +/- 5.6 mug/mg (P < 0.005). Crossed immunoelectrophoresis of extracts from both sensitive and resistant strains revealed a secondary sialic acid-containing antigen that was electrophoretically different from both the major K-1 antigen and a reference group B meningococcal antigen. This negatively charged secondary antigen was susceptible to Clostridium perfringens neuraminidase degradation and reacted only with IgG whereas the major K-1 antigen reacted only with IgM. This antigen was detected in the extracts of resistant isolates only at 10(10) but not at 10(9) colony-forming units per milliliter. This study demonstrates that (i) the degree of phagocytosis of bacteremic E. coli K-1 isolates is inversely associated with K-1 content, and (ii) more easily phagocytosed (sensitive) K-1 isolates have greater amounts of an additional sialic acid-containing antigen that appears to be unrelated to the previously described O acetyl K-1 antigen.
大肠杆菌K-1的血培养分离株中有80%对正常人粒细胞和新鲜血清的体外调理吞噬作用具有抗性。为了确定20%的菌血症K-1大肠杆菌对吞噬作用敏感的基础，我们研究了抗性和敏感分离株之间K-1抗原含量在定量和定性免疫化学方面可能存在的差异。我们通过超声处理制备了血培养K-1大肠杆菌的提取物，并使用交叉反应的马抗B群脑膜炎球菌血清，通过火箭免疫电泳法测定每毫克细菌干重中的K-1多糖含量。我们使用免疫球蛋白组分以及从B群抗血清中分离出的免疫球蛋白G（IgG）和IgM，通过交叉免疫电泳评估抗原含量的定性差异。三种不同的抗性K-1分离株的平均K-1含量为48.5±7.6微克/毫克干细菌（±标准差），三种敏感分离株的含量为23.2±5.6微克/毫克（P<0.005）。敏感和抗性菌株提取物的交叉免疫电泳显示，存在一种含唾液酸的次要抗原，其电泳图谱与主要K-1抗原和参考B群脑膜炎球菌抗原均不同。这种带负电荷的次要抗原易被产气荚膜梭菌神经氨酸酶降解，且仅与IgG反应，而主要K-1抗原仅与IgM反应。该抗原仅在每毫升10^10而非10^9菌落形成单位的抗性分离株提取物中被检测到。本研究表明：（i）菌血症大肠杆菌K-1分离株的吞噬程度与K-1含量呈负相关；（ii）更易被吞噬（敏感）的K-1分离株含有更多的另一种含唾液酸抗原，该抗原似乎与先前描述的O-乙酰基K-1抗原无关。
