Zhang W, Mellmann A, Sonntag AK, Wieler LH, Bielaszewska M, Tschäpe H, Karch H, Friedrich AW (2007): Structural and functional differences between disease-associated genes of enterohaemorrhagic Escherichia coli O111
Int. J. Med. Mikrobiol. 297 (1): 17-26.

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 11 and designated fliC_H8, fliC_H10 and fliC_H11. The IS629 insertion element was present, identically located, in six epidemiologically unrelated isolates with fliC_H8. The prevalence of the fliC genotypes in the 72 EHEC O111 strains were fliC_H8 (89%), fliC_H10 (7%) and fliC_H11 (4%). Within these fliC genotypes, a high degree of homogeneity for the presence of disease-associated genes was found. The adhesins-encoding genes eae and efa-1 were present in all strains with fliC_H8 and fliC_H11, but absent from strains with fliC_H10. The latter strains have not been reported previously. Strains with fliC_H10 and fliC_H11, but not those with fliC_H8, retained intact cadA and cadC loci and decarboxylated lysine. Three different stx genotypes including stx₁, stx₂ and stx₁/stx₂ were determined among the 72 EHEC O111. We observed a significant increase over time in the frequency of strains harbouring both stx₁ and stx₂. The presence of stx₂ both alone and in combination with stx₁ was significantly (χ²=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.