Diagnosis of Shiga Toxin-Producing Escherichia coli Infections/Die Diagnostik von Shiga Toxin-produzierenden Escherichia coli-Infektionen

Abstract

Shiga toxin-producing E. coli (STEC) cause a spectrum of diseases ranging from watery diarrhea through hemorrhagic colitis to hemolytic uremic syndrome (HUS). Most STEC strains cannot be identified using conventional culture procedures. The exception is STEC O157:H7, which grows in colonies of typical morphology on certain selective culture media due to its inability to ferment sorbitol and to produce b-Dglucuronidase. Sorbitol-fermenting E. coli O157:H ± and STEC of the major non-O157 serotypes, of which most ferment sorbitol, cannot be distinguished on such media. Among various virulence factors, the ability to produce Shiga toxins is a common characteristic of all STEC. The E. coli Shiga toxin family includes two major types, Stx1 and Stx2, and several toxin variants termed Stx1c, Stx2c, Stx2d, Stx2e and Stx2 f. The aim of the STEC laboratory diagnosis is the detection of Shiga toxins, which is achieved at three levels. At the first level, STEC screening is performed using culture on comercially available selective media and commercial enzyme immunoassays with enriched stool cultures. The detection of the toxin by an enzyme immunoassay must be followed by the isolation and characterization of the STEC isolate at the second level with the aim to confirm Shiga toxin production. The Shiga toxin colony immunoblot assay represents an effective, serotype independent, commercially available method for the isolation of STEC. In this method, Shiga toxin-positive colonies are identified using monoclonal antibodies. At the third step, subtyping of the STEC isolates is performed for epidemiological purposes, especially for STEC surveillance. This subtyping is usually done by National Reference Centers. In patients with HUS, the bacteriological detection of STEC may fail because the number of STEC in stool may be extremely low. In such cases, selective enrichment using immunomagnetic separation is recommended. In case of negative stool culture, the detection of specific serum antibodies against lipopolysaccharides of the major HUS-associated STEC serogroups, e. g. O157, is recommended.

Prevalence and Antimicrobial Resistance Profile of Diarrheagenic Escherichia coli from Fomites in Rural Households in South Africa

“…Sequences of Stx1 and Eagg gene fragments identified in this study were related to reference strains associated with infections such as hemolytic uremic syndrome (HUS) and diarrhea in patients from Egypt, South Africa, China, Japan, USA, and the UK [ 66 , 67 , 68 , 69 , 70 , 71 , 72 ], suggesting that Stx1 and Eagg strains found in this study may pose a threat to human health. The first outbreak of human Stx1 disease in South Africa occurred in 1992, a decade after the first outbreak in the United States of America [ 73 ].…”

“…Enterotoxigenic E. coli and EAEC are significantly associated with hemolytic uremic syndrome (HUS), urinary tract infection, and diarrhea worldwide [ 66 , 67 ]. E. coli strains have been classified based on genetic and evolutionary relationships into four main phylogroups (A, B1, B2, and D).…”