Genetic diversity among Escherichia coli isolates carrying f18 genes from pigs with porcine postweaning diarrhea and edema disease.

Multilocus enzyme electrophoresis was applied to detect allelic variation and multilocus genotypes (electrophoretic types [ETs]) among 43 Escherichia coli isolates from weaned pigs suffering from edema disease or from diarrhea. ETs were analyzed in relation to O serogroups and virulence genes (sta, stb, lt, stx2, and f18) by DNA hybridization. Genomic diversity was the lowest in serogroup O138, while virulence genes (stx2 and f18) were the most uniform in serogroup O139. In general, the serogroups or toxin and F18 fimbria types were not related to selected ETs, suggesting that the toxin and f18 fimbria genes in E. coli isolates from pigs with postweaning diarrhea or edema disease occur in a variety of chromosomal backgrounds.