| Pathogenic Escherichia coli {E.coli) are important intestinal pathogens in both humans and animals, including mainly enterotoxigenic E. coli (ETEC) and verotoxigenic E.: coli (VTEC). By adhering to the specific receptors, ETEC and VTEC colonize the small intestine for secreting enterotoxins and verotoxin and inducing post-weaning diarrhoea and oedema disease, respectively. Both diseases have economic significance due to mortality and decreased growth rates.To investigate the molecular epidemiology of virulent factors of pathogenic El coli, a total of 240 E. coli isolates were obtained from weaned piglets with diarrhea (140 isolates), edema (76 isolates) and diarrhea/edema (24 isolates). Among the 164 isolates searally typed, 116 isolates belonged to 20 different serogroups with 0139 as the dominant serogroup (40.24%). Different pairs of primers corresponding to the specific regions of genes coding for LT-I, ST-I, ST-II, Stx 1, Stx2, Stx2e, K88, F41, K99, 987P and F18 were designed for identifying toxin-producing and/or fimbria-expressing E. coli by multiplex- or duplex-PCR. Among 240 isolates tested, 108 isolates; (45%) were toxin gene-positive, including 60 VTEC, 24 VTEC/ETEC and 24 ETEC. No Stxl+ or Stx2+ E.coli were found. In addition, 78.95% of isolates from edematous piglets were VTEC, 100% of isolates from edematous and diarrheic piglets were VTEC/ETEC, while only 17.14% of those from edematous and diarrheic piglets were ETEC. These indicate that VTEC or VTEC/ETEC were mpre frequently (84%) associated with edema, while ETEC or VTEC/ETEC were relatively frequently! (29.27%) associated with diarrhea. Finally, the association pattern between O serogroup and enterot&xin showed that the stx2e gene was more prevalent in 0139, 0138, 0135, 0141, 05, O80, 073 and 0161 E. coli, while the st-I gene was more prevalent in 0139. 0141 and 0161 E. coli. Stx2e+ E. coli belonged mainly to 0139 serogroup.Among 216 isolates identified by PCR, 72 isolates (30%) were fimbriaei-positive, including 9 K88 + K99+F41-positive isolates from diarrheic piglets, 53 F18ab-positive isolates mainly from VTEC and VTEC/ETEC, and 10 F18ac-positive isolates mainly from VTEC/ETEC. In addition, F18ab gene was more frequently detected in VTEC (61.67%) or VTEC/ETEC 02.50%) than in ETEC (4.17%), while F18ac gene was more frequently detected in VTEC/ETEC (33.33%) than in ETEC (8.33%) or VTEC (0%). Furthermore, F18ab was more frequently associated with enterotoxin Stx2e-producing isolates, whereas F18ac was more frequently with enterotoxin ST-I-producing isolates. These results suggest that the PCR established in this experiment is a more reliable method for identification of fimbrial adhesin-producing E.coli and that F18 is a moire important virulence factor of VTEC and VTEC/ETEC.To investigate the distribution of LEE pathogenicity island and high pathogenicity island (HPI) of Yersinia enterocolitica in E.coli from weaned piglets, intimin gene {eaeA) and high molecular weight protein 2 (HMWP2) gene (irp2) of PAI and the pesticin receptor (FyiiA) gene (fyuA) and the boundary genes {tRNA-Asn-intB) of HPI were submitted to PCR amplification. Among 240 isolates tested, 12.08% were LEE- and HPI-positive, 16.25% were LEE-positive and only 4.58% wereHPI-positive. 20.71% of isolates from diarrheic piglets were LEE and HPI double positive, which was not detected in isolates from edematous or edematous/diarrheic animals. LEE gene was more frequently detected in isolates from edematous/diarrheic piglets (50%) than in those from edematous swine (6.58%) or diarrheic swines (15.71%). Further more, LEE or HPI or LEE+HPI was more frequently detected in non-enterotoxin-producing isolates from diarrheic animals. Finally, 27.5% of isolates were demonstrated by PCR to have fyuA gene deletion and asn-tRNA gene linkage to HPI, suggesting 75.2% of HPI+isolates were fyuA positive with gene linkage to asn-tRNA. Sequence analysis of randomly selected PCR products showed that eaeA gene of 5 isolates was 100%, irp2 gene of 7 isolates was 98.2%, fyuA gene of 5 isolates was 98.3% and A...
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