Abstract： Some Escherichia coli strains were isolated from swine colibacillosis in China during 2000 to 2005. They reacted with K88 a specific monoclonal antibody while without K88 b, c and d specific monoclonal antibodies in the slide agglutination test, respectively. O149 was common O serogroup of E. coli and 100.0%(16/16) strains possessed the genes of estII in this study. These isolates were identified with K88ac variant by cross-absorbed rabbit antisera to K88ac fimbria. The apparent molecular weight of K88ac antigens purified from these isolates was about 26 kD in SDS-PAGE, and experienced a positive reaction with the rabbit antisera absorbed with K88ac reference strain by Western blot. The faeG gene was amplified from the genomic DNA of SEC464, SEC525, SEC586, SEC799 and SEC910 by PCR. Alignment analysis of major FaeG subunits of the K88ac fimbria of these isolates showed some differences in amino acid composition comparing with those of K88ac reference strains, implying that the antigenic differences between these isolates and reference strains were due to the mutation of major subunits of the fimbria. Comparison of the sequences of amino acids of the major units showed that the percent identity was 97.7% ~99.6% among those isolates in amino acid sequences of major subunit FaeG, and 90.0%~91.6% comparing with K88ab reference strains, 94.6%~96.6% with K88ac reference strains, 87.0%~88.9% with K88ad reference strains, respectively. These results revealed that K88ac fimbrial antigens experienced some variations comparing with those of K88ac reference strains.
