Virulence properties of enterotoxigenic Escherichia coli O8: KX105 strains isolated from diarrheic piglets

Abstract

Twenty-two enterotoxigenic Escherichia coli (ETEC) O8:KX105 strains isolated from 1- to 7-week-old diarrheic piglets were examined for virulence properties. Thirteen strains caused acute watery diarrhea in orally infected, colostrum-deprived newborn piglets, whereas the remaining nine did not. The enteropathogenic strains colonized the small intestine, albeit with lower intensity than classical porcine ETEC. They produced the heat-stable STb and heat-labile LT enterotoxins, whereas the nonenteropathogenic strains produced the STb enterotoxin alone. None of the E. coli O8:KX105 strains exhibited mannose-resistant hemagglutination with erythrocytes from 12 species. Ten of the enteropathogenic and two of the nonenteropathogenic strains were positive for mannose-sensitive hemagglutination. These strains produced rodlike fimbriae 3 to 5 nm in diameter, whereas no fimbriae were detected on the other strains. None of the 22 strains produced the fimbrial antigens F4, F5, F41, F2, F3, FY(Att 25), and F165. Of the 13 enteropathogenic strains, 10 expressed the F6 antigen in the intestines of infected piglets but not in cultures. The other three enteropathogenic strains apparently lacked all of the known fimbrial antigens from porcine ETEC.

Pathotypes and serogroups of enterotoxigenic Escherichia coli isolated from pre-weaning pigs in north Vietnam

“…Similar strains that lack recognized fimbriae belonging to O8 and additional serogroups, including O101, O139, O138, O141, O147, O149 and O157, have been noted in studies from other countries, including Japan (Nakazawa et al, 1987), Sweden (Soderlind et al, 1988) and Denmark (Ojeniyi et al, 1994). However, it is unusual to find the production of LT enterotoxin associated with strains other than F4-or F18-positive ETEC (Harel et al, 1991;Ojeniyi et al, 1994;Wilson & Francis, 1986), with a few notable exceptions (Broes et al, 1988;Lund et al, 1982). This makes the O8 strains identified in the present study even more unusual in that they possess LT in association with STa and STb enterotoxins.…”

Pathogenicity of an Escherichia coli O115:K"V165" mutant negative for F165(1) fimbriae in septicemia of gnotobiotic pigs

“…Transmission electron microscopy and scanning electron microscopy were performed on ileum, cecum, and colon segments fixed in 5% glutaraldehyde overnight at 4°C and washed at room temperature in 0.1 M cacodylate buffer (pH 7.0) containing 0.15% (wt/vol) ruthenium red. Segments were processed for electron microscopy as previously described (2,24).…”

Experimental infection of newborn pigs with an attaching and effacing Escherichia coli O45:K"E65" strain

“…Strain 4725 was tested for enterotoxigenicity by using the gut-loop technique in 5-to 6-week-old pigs (3). The strain was examined for production of the enterotoxins STa, STb, and the heat-labile enterotoxin by using the infant mouse test, the gut-loop test in 5to 6-week-old weaned pigs, and tissue culture assays with Y1, CHO, and Vero cells, respectively (3,11). Shigalike toxin and cytolethal distending toxin production were determined in Vero and CHO cells (11).…”