Comparison of Enterohemorrhagic <i>Escherichia coli</i> (EHEC) O157 and EHEC Non-O157 Isolates from Patients with Diarrhea in Korea

Abstract

Enterohemorrhagic Escherichia coli (EHEC) is recognized as an important foodborne pathogen that causes several gastrointestinal illnesses, such as bloody or nonbloody diarrhea, hemorrhagic colitis (HC), and hemolytic uremic syndrome (HUS) in humans (1). Although more than 70 different pathogenic serotypes of Shiga toxin-producing E. coli (STEC) have been described to date, studies of EHEC prevalence have focused primarily on E. coli O157:H7 (2). However, recent epidemiological studies have reported that several non-O157 STEC serogroups are linked to severe disease in humans (2-5). In the present study, we compared EHEC O157 and non-O157 isolates from Korean patients with diarrhea to further characterize the EHEC isolates in these patients by serotype.A total of 231 human clinical isolates (47 EHEC O157 strains and 184 EHEC non-O157 strains) were collected between 2003 and 2011 through a routine surveillance system, which involved laboratory testing of stool samples from patients with diarrhea, isolation of bacteria from clinical specimens, and identification of EHEC isolates. The EHEC strains were characterized for the presence of 10 virulence genes, namely the EHEC attachment-effacement gene (eaeA), hemolysin genes (hlyA, ehx, and clyA), adhesion genes (iha, saa, efa1, tir, and toxB) (6). The EHEC strains were examined for the presence of antibiotic resistance determinants using the VITEK2 system (BioMérieux, St. Louis, MO, USA). The Clinical and Laboratory Standards Institute breakpoints were used for interpretation of susceptibility to antimicrobial agents. E. coli ATCC 25922 was tested as a quality control strain. In this study, GraphPad Prism ver. 5 (La Jolla, CA, USA) was used for statistical analysis. P-values of ≤ 0.05 were considered to represent statistical significance.The results of characterization of EHEC O157 and EHEC non-O157 strains are shown in Table 1. The Shiga toxin (Stx) is essential for the development of bloody diarrhea and HC; Stx2 plays a more important role than Stx1 in the development of HUS (7). The 231 EHEC strains represented 3 different enterotoxin profiles: SUMMARY:We compared 47 enterohemorrhagic Escherichia coli (EHEC) O157 isolates with 184 EHEC non-O157 isolates from Korean patients with diarrhea. In the O157 group, the strains harboring both Shiga toxin genes (stx1 and stx2) were detected with highest frequency, whereas the strains harboring only stx1 gene were most frequently detected in the non-O157 group. Eight virulence genes (eaeA, hlyA, ehx, iha, efa1, tir, toxB, and espA) were found to show a higher frequency of occurrence in the O157 group than in the non-O157 group. In addition, the symptom of bloody diarrhea was exhibited at a higher rate in the O157 group (51.1%) than in the non-O157 group (16.8%). Our findings demonstrate that EHEC O157 strains are more frequently implicated in cases of bloody diarrhea in the Korean population than EHEC non-O157 strains.

Comparative genomic analysis of 127 Escherichia coli strains isolated from domestic animals with diarrhea in China

“…The stx subtype of all 12 swine isolates was stx 2e . No putative EHEC VFs, including eaeA , hlyA , cnf1 , and cnf2 [12, 13] were detected in STEC isolates in this study.…”

Epidemiology of Non-O157 Shiga Toxin-Producing Escherichia coli in the Province of Alberta, Canada, from 2018 to 2021

“…A study from Switzerland recorded that the top four serogroups in their country were O103, O26, O91 and O80 [18]. Data from Korea showed O103, O26, O91 and O8 [19] and Japan reported O26, O111, O103, O121 and O145 [20] as their predominant serogroups. British Columbia, Canada (located west of Alberta) found their top serogroups to be O121, O26, O103, O117 and O111 [21].…”

Enterohemorrhagic Escherichia coli Tir inhibits TAK1 activation and mediates immune evasion

“…EHEC generates attaching and effacing (AE) lesions to colonize the intestine, damage the epithelium, and promote diarrheal illnesses [21,22]. The translocated intimin receptor (Tir) from EHEC is an important virulence protein that is injected into the plasma membrane of host cells via a type III secretion system (T3SS) [23][24][25][26]. Proteases produced by EHEC and the prevalent human commensal Bacteroides thetaiotaomicron can modulate T3SS function by cleaving proteins in the EHEC T3SS translocon [27].…”