Variation in the Genomic islands of porcine enteropathogenic E. coli strains of serogroup O45 revealed by CGH and PCR.. Variation in the Genomic islands of porcine enteropathogenic E. coli strains of serogroup O45 revealed by CGH and PCR.

Background: Members of E. coli serogroup O45 are porcine enteropathogenic E. coli (PEPEC) strains which cause post-weaning diarrhea and produce characteristic attaching and effacing (A/E) lesions. Most of O45 PEPEC strains possess the locus of enterocyte effacement (LEE), encoding the virulence factors for A/E lesions, and often possess the paa gene, which is thought to contribute to the early stages of PEPEC virulence. Methodology: Nine O45 PEPEC strains and a rabbit enteropathogenic (REPEC) strain, known to produce A/E lesions, were characterized using an E. coli O157-E. coli K12 whole genome microarray and a virulence gene-specific microarray, and by PCR experiments. Results: Based on their virulence genes profiles, the 10 strains were characterized as atypical EPEC. The differences in their genomes pointed to two distinct evolutionary groups of O45 PEPEC, Group I and Group II, and to the contribution these genetic differences have on virulence in pigs. Group I contained the REPEC strain and four O45 PEPEC strains known to induce severe A/E lesions in challenged pigs whereas Group II was composed of five other O45 PEPEC strains which induced less severe or no A/E lesions in challenged pigs. Significant differences between Groups I and II were found in the presence or absence of 50 O-Islands (OIs) or S-loops and 13 K-islands (KIs) or K-loops, including the virulence-associated islands OI#1 (S-loop#1), OI#47 (S-loop#71), OI#57 (S-loop#85), OI#71 (S-loop#108), OI#115, OI#122, and OI#154 (S-loop#253). Overall design: 10 samples, with two microarrays per sample. Each microarray includes duplicates of every spot.