Molecular detection of sorbitol-fermenting Escherichia coli O157 in patients with hemolytic-uremic syndrome

Abstract

Shiga-like toxin-producing Escherichia coli strains of serogroup 0157 were identified in 26 of 104 patients with hemolytic-uremic syndrome and in 18 of 668 patients with diarrhea. All strains were identified by colony hybridization with DNA probes complementary to Shiga-like toxin I and Shiga-like toxin II gene sequences and characterized by biochemical tests and serotyping. Seventeen of these 44 patients had E. coli 0157 strains which were unusual because they fermented sorbitol within 24 h of incubation and were positive for 1-glucuronidase activity. Culture filtrates of these sorbitol-fermenting strains were highly toxic to Vero cells in culture. Serological tests and DNA analysis performed by restriction endonuclease digestion of B-subunit toxin genes revealed that all 17 isolates produced Shiga-like toxin II. Although by using molecular probes we established a high frequency of sorbitol-fermenting E. coli 0157 strains in the patients we examined, further studies on the prevalence of such isolates in other areas of endemic disease are clearly warranted. Shiga-like toxin (SLT)-producing Eschenchia coli 0157 is now well recognized to be associated with sporadic cases and outbreaks of diarrhea, hemorrhagic colitis, and hemolytic-uremic syndrome (HUS). Aside from E. coli 0157, SLT production has also been observed in other serogroups of E. coli (12, 13). Strains of serotype 0157:H7 share some phenotypic characteristics in that they do not ferment sorbitol within 24 h of incubation (7, 14, 15, 17, 20) and show a negative reaction for

Probing genomic diversity and evolution of Escherichia coli O157 by single nucleotide polymorphisms

“…Single nucleotide polymorphisms in E. coli O157 Genome Research 759 www.genome.org G5101, which distinguished pO157s of these two atypical strains. Absence of toxB in 493/89 apparently did not alter its infectivity because 493/89 had been implicated in several outbreaks of HUS in both Germany and central Europe (Gunzer et al 1992;Bitzan et al1993). However, deletion of the toxB gene combined with mutations in other virulence-associated genes (e.g., 12-bp deletion in the flagellar master control gene, flhC) probably led to an altered epithelial cell adherence capability of this nonmotile STEC O157 strain (Tatsuno et al 2001;Monday et al 2004).…”

Virulence factors of Escherichia coli O157 and other Shiga toxin-producing E. coli

“…Escherichia coli O157 isolates do not ferment sorbitol within 24 h and do not produce b-glucuronidase, characteristics exploited in di¡erential media for their isolation (Strockbine et al 1998). However, sorbitol-fermenting, b-glucuronidase-producing toxigenic E. coli O157 have been isolated, and such organisms may account for 50 % of E. coli O157 infections in Germany (Gunzer et al 1992); these organisms represent a distinct clone of E. coli O157 (Whittam 1998). Most isolates of E. coli O157 produce Shiga toxin 2 (Stx2) only; Shiga toxin 1 (Stx1) and Stx2 producers are occasionally found but isolates producing Stx1 only are rare (Gri¤n and Tauxe 1991).The majority of E. coli O157 isolates possess a large 60 -MDa plasmid designated pO157 (Schmidt et al 1994), a terminology used in this review.…”

Methods for the detection and isolation of Shiga toxin-producingEscherichia coli

“…It is important to note that when culture methods based on sorbitol-negative and GUO-negative characteristics are used, several STEC strains will be missed and the number of infections with these strains will probably be underestimated. Indeed, sorbitol-and GUO-positive E. coli 0157 have been isolated from patients in Germany (Gunzer et al 1992). Pathogenic sorbitol-fermenting strains of E. coli 0157:H-have also been isolated from patients with HUS in other parts of Europe (Feng 1995), and these strains would not be detected with SMAC agar.…”