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

TLDR

High‑frequency sorbitol‑fermenting E. coli O157 strains were detected in the examined patients, indicating a need for further prevalence studies in other endemic regions. All strains were identified by colony hybridization with DNA probes targeting Shiga‑like toxin I and II gene sequences, followed by biochemical testing and serotyping.

Abstract

Shiga-like toxin-producing Escherichia coli strains of serogroup O157 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 O157 strains which were unusual because they fermented sorbitol within 24 h of incubation and were positive for beta-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 O157 strains in the patients we examined, further studies on the prevalence of such isolates in other areas of endemic disease are clearly warranted.