对FC株猪源性肠毒素型大肠杆菌致病因子的研究

FC菌株是一株从腹泻仔猪粪便中分离的肠毒素型大肠杆菌(Enterotoxigenic E.coli,ETEC)。在MRHA反应中,本菌能凝集人O型、豚鼠、马、绵羊、牛、鸡和兔的红细胞,对人O型和豚鼠红细胞有很高的血凝性,血抗K88和K99血清不能抑制其对豚鼠和绵羊红细胞的血凝。在体外小肠上皮细胞吸附试验中,本菌对仔猪小肠上皮细胞具有强烈的吸附作用;透射电镜和扫描电镜观察证实了FC株菌除表面具有一种纤毛样结构外,还能定居在仔猪小肠段。血清学试验结果表明,本菌的O抗原属于O101。K88和987P两种抗血清均不能凝集本菌,而K99和F41抗血清均可凝集。对纯化的FC株菌粘着素抗原作等电聚焦和聚丙烯酰胺凝胶电泳分析,结果表明,该菌的粘着素是由等电点分别为4.61和9.78,分子量分别为29500和17500的两种蛋白质抗原所组成。此外,用乳鼠胃内投服试验和兔肠结扎试验证明,该菌只产生热稳定肠毒素。总之,本菌是一株能产生ST的K99,F41的肠毒素型大肠杆菌。

A STUDY ON PATHOGENIC FACTORS OF STRAIN FC OF ENTEROTOXIGENIC E. COLI ISOLATED FROM NEWBORN PIGLETS WITH DIARRHEA

Investigations on two pathogenic factors of a ETEC strain ( designated FC ) isolated from piglets with diarrhea were carried out in this paper. The strain FC was able to hemagglutinate erythrocytes of human group O, guinea pig, horse, sheep, calf, chicken and rabbit, in the mannose-resistant hemagglutination test. among hemagglutinating cryth-rocytes, the hemagglutination activity with human group 0 and guinea pig erythrocytes was the strongest. Moreover, the hemagglutination activity with sheep and guinea pig erythrocytes by this strain was not inhibited by antiserum to K99 and K88 respectively. The strain FC with enteropathogenic characteristics could strongly attach to the epithelial cells derived from small intestine of piglets, in the brush-border adhesion test in vitro.Newborn piglets that were orally infected with the strain FC showed severe diarrhea or died within 24 hours. By using transmission and scanning electron microscopic observations, it was clearly demostrated that the bacteria not only had the ability to colonize in small intestine but also possessed the pilus-like structure on their surface. Through serological comparisons, it was also indicated that the strain FC did not react with antiserum specific for K88 and 987P, but it did react with antiserum specific for K99 and F41. The purified adhesive antigen of strain FC was analyzed dy isoelectric focusing and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) , and two different proteins with isoelectric point of 4.61 and 9.78 and molecular weight of 29500 and 17500 were found.Finally. the strain FC was able to produce the heat-stable enterotoxin as revealed in the suckling mouse test. The fact suggested that strain FC be an ETEC strain of pig-origined, bearing both K99 and F41 fimbral ad-hesins.