Development of a monoclonal antibody-based co-agglutination test to detect enterotoxigenic Escherichia coli isolated from diarrheic neonatal calves

Escherichia coli (E. coli) strains were collected from young diarrheic calves in farms and field. Strains that expressed the K99 (F5) antigen were identified by agglutination tests using reference antibodies to K99 antigen and electron microscopy. The K99 antigen from a selected field strain (SAR-14) was heat-extracted and fractionated on a Sepharose CL-4B column. Further purification was carried out by sodium deoxycholate treatment and/or ion-exchange chromatography. Monoclonal antibodies to purified K99 antigen were produced by the hybridoma technique, and a specific clone, NEK99-5.6.12, was selected for propagation in tissue culture. The antibodies, thus obtained, were affinity-purified, characterized and coated onto Giemsa-stained Cowan-I strain of Staphylococcus aureus (S. aureus). The antibody-coated S. aureus were used in a co-agglutination test to detect K99+ E. coli isolated from feces of diarrheic calves. The specificity of the test was validated against reference monoclonal antibodies used in co-agglutination tests, as well as in ELISA. Specificity of the monoclonal antibodies was also tested against various Gram negative bacteria. The developed antibodies specifically detected purified K99 antigen in immunoblots, as well as K99+ E. coli in ELISA and co-agglutination tests. The co-agglutination test was specific and convenient for large-scale screening of K99+ E. coli isolates.     

几种免疫标记检测法对炭疽菌诊断的比较研究

本文采用免疫荧光标记技术、免疫酶标技术和葡萄球菌蛋白A(Staphylococcal Protein A.SPA)协同凝集反应对炭疽杆菌进行了快速诊断比较试验,结果均收到比较满意的效果,但以用SPA协同凝集反应,更表现出快速、简便、敏感、特异等优点。     

Comparative grouping of mastitis Streptococci by means of co-agglutination and precipitation

Two hundred bovine mastitis streptococcal strains belonging to groups B, C, E, G and L were tested comparatively by means of the co-agglutination and precipitation technique. Identical results were obtained with the two tests in 191, or 95.5 %, of the strains. Six strains, which could not be grouped by co-agglutination, proved to belong to group B when grouped by precipitation. On the other hand, one strain which proved to belong to group G and two strains to group L when grouped by co-agglutination, could not be grouped by precipitation. Some cross-reactivity was observed between groups A and C, B and G, B and L. Only a few L strains showed marked cross-reactivity which was not easily distinguished from specific reactions. However, the cross-reactivity ought to be eliminated by dilution or adsorption. Using the precipitation test as a supplementary method, the easy and rapid co-agglutination test was found to be a suitable procedure for routine grouping of mastitis streptococci.     

利用间接免疫荧光染色和协同凝集技术检测梨火疫病菌

提取梨火疫病菌 (0 0 5 6菌株 )的脂多糖免疫家兔 ,获得抗血清 ,建立了检测梨火疫病菌的间接免疫荧光染色和协同凝集检测技术 ,对梨火疫病菌的不同菌株和人工接种发病样品实施了检测。结果表明 ,这 2种方法可以准确、灵敏地检测梨火疫病菌及样品 ,方法简单、快速、实用 ,可以在中国口岸推广使用 ,减少梨火疫病进入中国的风险。