Association of Genomic O Island 122 of <i>Escherichia coli</i> EDL 933 with Verocytotoxin-Producing <i>Escherichia coli</i> Seropathotypes That Are Linked to Epidemic and/or Serious Disease

TLDR

VTEC strains are grouped into five seropathotypes (A–E) according to their association with human disease, outbreaks, and hemolytic‑uremic syndrome. The authors examined 70 VTEC strains for the presence of four OI‑122 virulence genes (Z4321, Z4326, Z4332, Z4333) using PCR and Southern hybridization. Complete OI‑122 was present in 40% of strains, with 100%, 60%, and 36% of seropathotypes A, B, and C (all HUS‑associated) versus 15% of D and 0% of E, a distribution that differed significantly between HUS‑associated and non‑HUS seropathotypes (P < 0.0001).

Abstract

ABSTRACT The distribution of EDL 933 O island 122 (OI-122) was investigated in 70 strains of Verocytotoxin-producing Escherichia coli (VTEC) of multiple serotypes that were classified into five “seropathotypes” (A through E) based on the reported occurrence of serotypes in human disease, in outbreaks, and/or in the hemolytic-uremic syndrome (HUS). Seropathotype A comprised 10 serotype O157:H7 and 3 serotype O157:NM strains. Seropathotype B (associated with outbreaks and HUS but less commonly than serotype O157:H7) comprised three strains each of serotypes O26:H11, O103:H2, O111:NM, O121:H19, and O145:NM. Seropathotype C comprised four strains each of serotypes O91:H21 and O113:H21 and eight strains of other serotypes that have been associated with sporadic HUS but not typically with outbreaks. Seropathotype D comprised 14 strains of serotypes that have been associated with diarrhea but not with outbreaks or HUS, and seropathotype E comprised animal VTEC strains of serotypes not implicated in human disease. All strains were tested for four EDL 933 OI-122 virulence genes (Z4321, Z4326, Z4332, and Z4333) by PCR. Negative PCRs were confirmed by Southern hybridization. Overall, 28 (40%) strains contained OI-122 (positive for all four virulence genes), 27 (38.6%) contained an “incomplete” OI-122 (positive for one to three genes), and 15 (21.4%) strains did not contain OI-122. The seropathotype distribution of complete OI-122 was as follows: 100% for seropathotype A, 60% for B, 36% for C, 15% for D, and 0% for E. The differences in the frequency of OI-122 between seropathotypes A, B, and C (associated with HUS) and seropathotypes D and E (not associated with HUS) and between seropathotypes A and B (associated with epidemic disease) and seropathotypes C, D, and E (not associated with epidemic disease) were highly significant ( P &lt; 0.0001).