Structural and functional differences between disease-associated genes of enterohaemorrhagic Escherichia coli O111

We analysed 72 clinical isolates of enterohaemorrhagic Escherichia coli (EHEC) O111 from patients with diarrhoea or haemolytic uraemic syndrome (HUS) isolated during the period from 1955 to 2005 and identified six motile strains (flagellar antigens 8, 10 and 11); the remaining 66 (92%) were nonmotile (NM) and could not be typed by conventional H serotyping. To improve subtyping methodologies, we determined genotypes of the flagellin-encoding fliC. Three fliC genotypes were found which were identical to those of motile EHEC O111 with H antigens 8, 10 and I I and designated fliC(H8), fliC(H10) and fliC(H11). The IS629 insertion element was present, identically located, in six epidemiologically unrelated isolates withfliC(H8). The prevalence of the fliC genotypes in the 72 EHEC O111 strains werefliC(H8) (89%), fliC(H10) (7%) andfliCH(11) (4%). Within these fliC genotypes, a high degree of homogeneity for the presence of diseaseassociated genes was found. The adhesins-encoding genes eae and efa-1 were present in all strains with fliCH8 and fliC(H11), but absent from strains with fliC(H10). The latter strains have not been reported previously. Strains with fliC(H10) and fliCH(11), but not those withfliCH8, retained intact cadA and cadC loci and decarboxylated lysine. Three different stx genotypes including stx(1), stx(2) and stx(1)/stx(2) were determined among the 72 EHEC O111. We observed a significant increase over time in the frequency of strains harbouring both stx(1) and stx(2). The presence Of stx(2) both alone and in combination with stx(1) was significantly (chi(2) = 23.16, P < 0.00001, CI95 [2.29; 9.76]) associated with HUS. Therefore, the emergence of EHEC O111 should be monitored carefully. We conclude that EHEC O111 strains can be differentiated using specific loci required for motility, adherence, Stx production, and lysine decarboxylation. The divergence within EHEC O111 makes it possible to subtype these emerging pathogens in the laboratory thereby providing a basis for further investigations into their ecological niches and survival capabilities. (c) 2006 Elsevier GmbH. All rights reserved.