Analysis of main virulence factor in haemolytic Escherichia coli isolated from diarrheal specimens of growing and finishing pigs

Abstract

A total of 70 haemolytic Escherichia coli strains isolated from 310 growing and finishing pigs with diarrhea in 27 porcine farms were screened for the analysis of main virulence factor. Porcine enterotoxigenic E. coli strains typically express K88 or F18 fimbria and heat-labile (LT) and/or heat-stable (STa, STb) enterotoxins. We examined the virulence factors of haemolytic E. coli strains for K88, F18, F41, 987P and K99 fimbrial genes; LT, STa, STb and Stx2e toxic genes isolated by a multiplex polymerase chain reaction (PCR). The haemolytic E. coli strains were found in 18 (66.7%) farms and 14.5% (45 of 70 haemolytic isolates) of isolates in 12 (44.4%) farms possessed at least one of virulence genes detected. Of 70 haemolytic E. coli isolates, 28 (40.0%) strains harbored fimbrial genes: K88 (32.1%), F18 (67.9%), F41 (0), 987P (0), F41 (0); toxic genes: LT (39.3%), STb(39.3%/2.4%), STa (39.3%/2.4%), Stx2e (57.1%/38.1%) in fimbrial and non-fimbrial isolates respectively. A total of 42 (60.0%) isolates carried no fimbrial genes, including 25 (59.5%) isolates that did not have any of the virulence genes. Interestingly, E. coli harboring Stx2e gene were prominant (30 of 45 virulent E. coli) and among those, 46.7% (14 of 30 Stx2e+) of isolates possessed with F18 fimbrial gene, whereas 53.3% (16 of 30 Stx2e+) were not harboring any fimbrial genes tested. These results suggest a diverse range of virulence genes associated with diarrhea in growing and finishing pigs.