| A crude extract of the adhesin F18ac from tbe reference Escherichia coli (E.coli) strain 2134 (0157:H19) was purified as described by Wu Xiaodong with modifications. After extraction by thermoelution, precipitation with 60% ammonium sulfate and dialysis against water, the washed sediment was analyzed by SDS-PAGE and presented one band of 17 kD. Spleen-derived B cells from the BALB/c mouse injected with the purified fimbrial antigens were fused with SP2/0 myeloma cells and one hybridoma cell line, named 19B4, was established by slide agglutination. Slide agglutination and western-blot confirmed that the monoclonal antibody (McAb) secreted by 19B4 were against tbe common antigenic determinant designated "a". The titre of its culture .supernatant and its ascitic fluid were 1:8 and 1:1024 in slide agglutination with 2134 as well as 107/86, the F18ab reference Kcoli respectively. The McAb 19B4 reacted specifically with both 2134and 107/86, while not with reference E.coli strains bearing F4 F5 F6 F41 adhesins or other F18 negative Kcoli strains and Salmonella Western-blot analysis proved that the McAb 19B4 could react simultaneously with the 15 kD subunit of F18ab pili from strain 107/86 and the 17 kD subunit of F18ac fimbriae from strain 2134. We concluded that the McAb recognized specifically the 'a' epitope of Fl8 pili.The McAb had been potentially used in slide agglutination to detect F18 pili antigens of field isolates from pigs with postweaning diarrhea 13.4% (29/215) and 8.4% (18/215) of these isolates were positive when they were cultured in Trypticase Soy Broth (TSB) and on Trypticase Soy Agar (TSA) respectively, and their 0 serogroups included both the usual serogroupes 0139,0141 and the unusual serogroupes 0107, O131 and O9. The results suggested that F18 maybe the common surface antigens on K coli strains isolated from pigs whh postweaning diarrhea, and it was easier to be detected when these isolates were grown in TSB than on TSA... |
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