鸽源产肠毒素大肠杆菌O55分离株的鉴定及其致病性研究

IDENTIFICATION AND PATHOGENICITY OF ENTEROTOXIGENIC ESCHERICHIA COLI O55 ISOLATED FROM INFECTED PIGEONS

本研究旨在了解鸽源致病性大肠杆菌O55分离株的分类及其致病性。首先,采用PCR方法对前期研究得到的6株分离菌毒力基因携带率进行检测;然后,选取毒力基因携带种类较多且与人类腹泻相关的O55分离株,经凝集试验、兔回肠结扎试验、乳鼠灌胃试验测定O55分离株黏附素、肠毒素基因是否表达;最后,以昆明鼠为试验动物,通过口服途径感染O55分离株进行致病性观察。结果显示:分离菌携带毒力基因fimH与papA均为100%(6/6),fyuA为66.7%(4/6),eaeA与iss均为50%(3/6),irp-2、fimC与tsh均为33.3%(2/6);O55分离株黏附素及肠毒素基因均表达;O55分离株对试验鼠多个脏器造成持续性损伤,以肝脏、肺脏、肾脏、空肠、回肠较为严重,抗原主要位于感染部位细胞质或细胞间质。该研究结果有助于了解鸽源产肠毒素大肠杆菌的致病特点,具有值得关注的公共卫生学价值。

To investigate the pathogenicity and classification of six O55 isolates from infected pigeons,their virulence genes of fyuA,irp-2,fimC,papA,tsh,eaeA,fimH and iss were detected with PCR.In this study,serum agglutination test was applied to detect the adhesin F5,rabbit intestinal-loop test and neonatal mouse intragastric test were employed to detect the enterotoxin.Using gavage method,mice were fed on O55 cultures of these isolates that were highly virulent and caused diarrhea in human beings.The results showed that fimH and papA genes were detected in all 6 strains,fyuA gene in 4 strains,eaeA and iss genes in 3 strains,and irp-2,fimC and tsh genes in 2 strains.These O55 isolates agglutinated F5 positive serum.Different degrees of damages were observed in mouse tissues,especially hearts,kidneys,lungs,jejunums and ileums.The O55 antigen was detected in all tissues and mainly located in cytoplasms and interstitial cell fluids.These results indicated that O55 isolates from the livers of diseased pigeons were enterotoxigenic E.coli and were strong virulent to mice.The data obtained from this study were helpful to understand the pathogenic characteristics of enterotoxigenic E.coli from pigeons and played public health significance.