Molecular analysis of Escherichia coli O157 strains isolated from cattle and pigs by the use of PCR and pulsed-field gel electrophoresis methods

Abstract

ABSTRACT:Fourteen Escherichia coli O157 strains isolated from cattle and pigs in Poland and in Germany were investigated, using PCR, for the genetic markers associated with Shiga toxin-producing E. coli (STEC). Only two strains, both of cattle origin, were positive for the fliC (H7) gene and could be classified as O157 : H7. Nine isolates had stx shiga toxin genes, either stx1 (1 strain), stx2 (4 isolates) or both (4 strains). e stx2-carrying samples were further subtyped by PCR for the stx2c, stx2d, and stx2e toxin variants. It was shown that all but one stx2-positive bacteria possessed the stx2c Shiga toxin gene type and one stx2 STEC isolate had the stx2d virulence factor subtype. e eaeA (intimin) gene was found in 9 strains (8 isolates from cattle and one strain from pigs); all of them harboured the genetic marker characteristic of the gamma intimin variant. e translocated intimin receptor (tir) gene was detected in 7 isolates tested and among them only one tir-positive strain was recovered from pigs. e ehly E. coli enterohemolysin gene was amplified in all but one strains obtained from cattle and only in one isolate of porcine origin. e genetic relatedness of the analysed E. coli O157 strains was examined by restriction fragment length polymorphism (RFLP) of chromosomal DNA digested with XbaI. Two distinct but related RFLP pattern clusters were observed: one with 9 strains (8 isolates of bovine origin and one strain obtained from pigs) and the other one comprises the remaining 5 E. coli isolates (4 of porcine origin and one strain recovered from cattle). e results suggest that pigs, besides cattle, may be a reservoir of E. coli O157 strains potentially pathogenic to humans. Moreover, epidemiologically unrelated isolates of the O157 serogroup, recovered from different animal species, showed a clonal relationship as demonstrated by the RFLP analysis.

Diverse Virulence Gene Content of Shiga Toxin-Producing Escherichia coli from Finishing Swine

“…The degrees of genetic relatedness of swine STEC strains to strains from other animal species differed in those studies, and most studies focused on STEC O157:H7 (60,(69)(70)(71). Here, we found that STEC O59:H21 strains, which predominated in this swine population, were closely related among pigs in the same cohort.…”

“…Our study is the first one to use PFGE to analyze STEC strains recovered from repeated samples collected from pigs, while most of the previous studies used PFGE to determine the genetic relatedness of STEC strains from swine and other species (60,(69)(70)(71)(72). The degrees of genetic relatedness of swine STEC strains to strains from other animal species differed in those studies, and most studies focused on STEC O157:H7 (60,(69)(70)(71).…”

Detection ofEscherichia coliO157 andEscherichia coliO157:H7 by the immunomagnetic separation technique andstx1andstx2genes by multiplex PCR in slaughtered cattle in Samsun Province, Turkey

“…E. coli O157 or E. coli O157: H7 isolates obtained from cattle carcasses or feces have also been found to contain at least one of the stx1 , stx2 , eaeA , hylA and fliC h7 genes [5,7,22,25,29,35,38,39,41]. In contrast to other countries, there has been only one study of carcasses reported in Turkey [21].…”

Shiga toxin-producingEscherichia coliin swine: the public health perspective

“…A Polish study reported that one swine STEC O157 strain clustered with STEC O157 strains from cattle at a similarity criterion of 80% based on PFGE patterns. The swine STEC O157 strain was from a weaned pig with diarrhea, and no other epidemiologic relationship was described between the swine and cattle STEC strains (Osek and Gallien, 2002).…”