Characterization of nonenterotoxigenic Escherichia coli strains producing F17 fimbriae isolated from diarrheic lambs and goat kids

Forty-five ovine and caprine nonenterotoxigenic Escherichia coli strains pr oducing F17-related fimbriae were characterized with respect to the fimbria l structural subunit and adhesin subtypes produced. In addition, several ch aracteristics related to the virulence of strains producing F17 fimbriae H- ere studied. Most of the strains (73%) possessed the f17cA structural subun it gene, whereas the f17aA and f17dA genes were detected only on three (6%) and two (4%) strains, respectively, The f17bA gene was not detected. All b ut one of these strains possessed the f17G genes of the adhesin subfamily I J. The only strain baring the f17G gene of subfamily I possessed the struct ural subunit gene f17dA. Sequencing of the f17A and f17G genes of four sele cted strains confirmed the association of f17cA and f17dA structural subuni t genes with the f17G genes of the adhesin subfamily II, These results indi cated that adhesins of the subfamily II are prominent among ovine and capri ne isolates and that thee are indistinctly associated with the F17 structur al subunit subtypes on these field strains. C31A- and CNF2-related genes we re not detected. Most of the strains adhered in vitro to ovine intestinal b rush borders (36 of 45) and agglutinated the erythrocytes of different spec ies in the presence of D-mannose (39 of 45), F17-positive strains produced colicin V (57%) and were resistant to the bactericidal effect of serum (91% ;) in significantly higher percentages than F17-negative strains (34% produ ced colicin V, and 66% were serum resistant). Thus, most of the studied ovi ne and caprine strains showed phenotypic characteristics of septicemic stra ins.