Phenotype and genotype of Escherichia coli isolated from pigs with postweaning diarrhea in Hungary.

A total of 205 Escherichia coli isolates from 88 diarrheal weanling (4- to 10-week-old) pigs from 59 farms were tested by slide agglutination for K88, K99, F41, and 987P antigens. K88 antigen was detected in 61% of the isolates representing 60% of the pigs and 56% of the farms. K88 antigen was associated with serogroup O149 and 91% of the K88+ isolates. K99, F41, and 987P were not detected. Of the K88- isolates, 70 were additionally tested by colony hybridization with DNA probes for adherence factors K88, K99, 987P, and F41 and for enterotoxin genes STaP, STaH, STb, and LT and by Vero cell assay for verotoxins (VT). The 70 K88- isolates could be divided into three categories: LT-, VT-, STaP+, and/or STb+ (34 isolates); LT-, STaP+, STb+, and/or VT+ (17 isolates); and nontoxigenic (19 isolates). Only one of the K88- isolates carried a known adherence factor (987P) detectable with DNA probes. Most of the STaP+ and STb+ isolates belonged to O groups O141, O147, and O157. All but 1 of the 17 VT+ isolates belonged to O groups O138, O139, O141, and O149. Only three of the VT+ strains were isolated from pigs with edema disease. We concluded that 73% of the K88- isolates had the capability to produce enterotoxins or VT that could have contributed to weanling pig diarrhea.