Replicon typing of F18 fimbriae encoding plasmids of enterotoxigenic and verotoxigenic Escherichia coli strains from porcine postweaning diarrhoea and oedema disease

Abstract

The presence of ®mbrial adhesin F18 is frequently found in enterotoxigenic Escherichia coli (ETEC) and verotoxigenic E. coli (VTEC) strains responsible for diarrhoea and oedema disease of weaned pigs. The F18 adhesin occurs in two antigenic variants: F18ab is characteristic of VTEC while F18ac is more typical for ETEC. F18 encoding plasmids of 17 phenotypically characterized porcine E. coli isolates (10 ETEC, 6 VTEC and 1 ETEC/VTEC) were tested with a DNA probe for F18 ®mbrial adhesin and with replicon probes for the RepFIa, RepFIb and for the RepFIc family of basic replicons. In all the cases, the F18 probe hybridized to only one plasmid band of size higher than 42 MDa. All F18 plasmids were determined to be unireplicon plasmids belonging to the RepFIc replicon family of the F incompatibility complex. There was no difference between F18ac plasmids of ETEC and F18ab plasmids of VTEC strains in terms of replicon type or subtype. However, the size of F18ab plasmids of the VTEC strains varied between 42 and 98 MDa, in contrast to F18ac plasmids of ETEC strains (constantly approximately 98 MDa). #

Pathogenomics of the Virulence Plasmids ofEscherichia coli

“…Later analysis of pTC found that it contained a putative pathogenicity island (PAI) with a 10-kb fragment containing genes encoding the ST enterotoxins (52). Mainil (51). Those authors also observed that variants of the F18 adhesin exist: F18ab-encoding plasmids, which were highly variable in their sizes within a population examined, and F18ac-encoding plasmids, which were found to be of a more consistent size.…”

“…The work of Couturier et al resulted in the development of an invaluable set of DNA probes specific for each known incompatibility group of the Enterobacteriaceae that allowed screening for replicon-associated regions that were unique to each known plasmid type (34). Based on these probes, others have devised PCR-based replicon typing schemes (25,51,67,89,107,173), which identify the major Inc types occurring among the Enterobacteriaceae. Further refinements of replicon-based plasmid classification are likely, as the influx of genome sequencing data continues to increase and thus clarifies our understanding of plasmid structure and also because novel plasmid groups continue to be identified (186).…”

Genome Sequences and Phylogenetic Analysis of K88- and F18-Positive Porcine Enterotoxigenic Escherichia coli

“…This plasmid also contained truncated remnants of an F transfer region and a mosaic of mobile genetic elements, suggesting that it is transfer deficient and might be constantly in flux due to insertion sequence-driven genetic recombination. Previous reports have identified F18 and K88 porcine ETEC virulence plasmids on multiple IncF-type plasmid replicons, suggesting that this particular plasmid may represent only one variant of F18 plasmids circulating among swine ETEC isolates (13,28). UMNF18 contained a second IncFIIA-like plasmid, pUMNF18_IncFV, that was 103 kb (see Fig.…”

Prevalence of enterotoxigenic Escherichia coli virulence genes from scouring piglets in Zimbabwe

“…Interestingly, a few Stx-2e toxin genes were present among E. coli isolates from diarrheic piglets without any clinical signs of edema disease. However, since Stx-2e was associated with F18 fimbriae genes, these are variants of F18ac, which are more typical of ETEC responsible for diarrhea in piglets (Fekete et al 2002). In addition, occurrence of Stx-2e toxin genes in conjunction with F18 fimbriae genes indicates that these pathogens persist in porcine population in Zimbabwe despite comparatively low incidence of edema disease in the country (M. Mavenyengwa, University of Zimbabwe, personal communication).…”