Comparison of putative virulence and fitness genes of stx-negative and stx-positive E. coli strains of serotypes O26:H11/NM, O103:H2/NM, O121:H19, O145:H28/NM, and O157:H7/NM.

aThe genes were detected by PCR as described in Materials and Methods. GenBank accession numbers: EHEC-hlyA (NC007414); cdt-V (AJ508930); iha (AF126104; AE005174); lpfAO26 (AB161111), lpfAO157/OI 141 (AE005174), lpfAO157/OI 154 (AE005174), sfpA (NC009602), efa1 (AE005174; AJ459584), sen (AE005174), pagC (AE005174), ter cluster (AE005174), irp2, fyuA (NC003143), eae (AE005174).bEHEC, enterohemorrhagic E. coli; CDT-V, cytolethal distending toxin V; Iha, iron-regulated gene A homologue adhesin; LpfAO26 and LpfAO157, major fimbrial subunits of long polar fimbriae of EHEC O26 and EHEC O157, respectively; LpfAO157 (OI 141) and LpfAO157 (OI 154), LpfA encoded on O island (OI) 141 and OI 154, respectively, of E. coli O157:H7 strain EDL933; Sfp, sorbitol-fermenting EHEC O157, plasmid-encoded; Efa1, EHEC factor for adherence; ShET2, Shigella flexneri enterotoxin 2; PagC, protein encoded by the phoP-activated gene C (pagC) of Salmonella enterica serovar Typhimurium.cNM, nonmotile; NSF, non-sorbitol-fermenting; SF, sorbitol-fermenting; stx−, stx-negative; stx+, stx-positive; n, number of strains tested; +, all strains tested (n) were positive for the gene; −, all strains tested (n) were negative for the gene; if a subset of the strains contained the gene, the percentage is given in parenthesis.dA complete efa1 gene (ca. 10 kb) was present as determined by PCR targeting the 3′, internal, and 5′ region, respectively [28].eOnly the 5′ region of efa1 was present. Strains O145:H28/NM contained either complete efa1 (two stx− and three stx+ strains) or only the 5′ efa1 region (three stx− and seven stx+ strains).fThe ter-positive strains contained all genes of the ter gene cluster present in EHEC O157:H7 [25] (terZ, terA, terB, terC, terD, terE, and terF).gBoth genes were always present or absent together.hThe indicated fliC genotype was present in all strains of each respective serotype including strains that expressed the H antigen and nonmotile strains; n.p., not performed (because all strains expressed the H19 antigen).