Infection by verocytotoxin-producing Escherichia coli

Abstract

Verocytotoxin (VT)-producing Escherichia coli (VTEC) are a newly recognized group of enteric pathogens which are increasingly being recognized as common causes of diarrhea in some geographic settings. Outbreak studies indicate that most patients with VTEC infection develop mild uncomplicated diarrhea. However, a significant risk of two serious and potentially life-threatening complications, hemorrhagic colitis and the hemolytic uremic syndrome, makes VTEC infection a public health problem of serious concern. The main reservoirs of VTEC appear to be the intestinal tracts of animals, and foods of animal (especially bovine) origin are probably the principal sources for human infection. The term VT refers to a family of subunit exotoxins with high biological activity. Individual VTEC strains elaborate one or both of at least two serologically distinct, bacteriophage-mediated VTs (VT1 and VT2) which are closely related to Shiga toxin and are thus also referred to as Shiga-like toxins. The holotoxins bind to cells, via their B subunits, to a specific receptor which is probably the glycolipid, globotriosyl ceramide (Gb3). Binding is followed by internalization of the A subunit, which, after it is proteolytically nicked and reduced to the A1 fragment, inhibits protein synthesis in mammalian cells by inactivating 60S ribosomal subunits through selective structural modification of 28S ribosomal ribonucleic acid. The mechanism of VTEC diarrhea is still controversial, and the relative roles of locally acting VT and "attaching and effacing adherence" of VTEC to the mucosa have yet to be resolved. There is increasing evidence that hemolytic uremic syndrome and possibly hemorrhagic colitis result from the systemic action of VT on vascular endothelial cells. The role of antitoxic immunity in preventing the systemic complications of VTEC infection is being explored. Antibiotics appear to be contraindicated in the treatment of VTEC infection. The most common VTEC serotype associated with human disease is O157:H7, but over 50 different VT-positive O:H serotypes have now been identified. The best strategies for diagnosing human VTEC infection include testing for the presence of free VT in fecal filtrates and examining fecal cultures for VTEC by means of deoxyribonucleic acid probes that specify genes encoding VT1 and VT2. Both methods are currently confined to specialized laboratories and await commercial development for wider use. In the meantime, most laboratories should continue to screen for the most common human VTEC serotype, O157:H7, using a sorbitol-containing MacConkey medium.

Distribution and characteristics of verocytotoxigenicEscherichia coliisolated from Ontario dairy cattle

“…They identified VT-positive isolates in samples from 21 Many serotypes of VTEC, other than 0 157. H7, have been isolated from humans with diarrhoeal disease or HUS, and the list is growing steadily [10].…”

“…Foods of animal origin may be contaminated with VTEC by contact with faeces of animals harbouring VTEC within their intestinal tracts. In particular, the frequent association between VTEC infection and the consumption of beef or dairy products suggests that dairy cattle, an important source of both meat and milk for human consumption, might be an important reservoir for human food-borne VTEC infection [4,5,10,11].…”

VerotoxinogenicCitrobacter freundiiassociated with severe gastroenteritis and cases of haemolytic uraemic syndrome in a nursery school: green butter as the infection source

“…was not available (see Table 2). Citrobacter freundii (5) Citrobacter freundii (2), E. coli (1) Citrobacter freundii (1), E. coli (1) Citrobacter freundii (4) Citrobacter freundii (7) Citrobacterfreundii (2), E. coli (1) Citrobacter freundii (3) Citrobacterfreundii (3) (see also [8,21]. t Number and size in Md, plasmid incompatibility groups in brackets.…”

“…Verotoxinogenic Escherichia coli (VTEC) strains of different serovars have been recognized as causative agents of severe gastrointestinal infections with lifethreatening post infectious syndromes such as haemolytic uraemic syndrome (HUS), thrombotic thrombocytopenic purpura (TTP) or haemorrhagic colitis (HC) [1]. The broad range of serovars necessitates a diagnostic approach different to the conventional serological or biochemical tests used in routine medical microbiological investigations.…”

Immunization with a Chimera Consisting of the B Subunit of Shiga Toxin Type 2 and Brucella Lumazine Synthase Confers Total Protection against Shiga Toxins in Mice

“…The clinical manifestations of EHEC infections range from watery diarrhea, or hemorrhagic colitis, to the most severe outcome, the life-threatening hemolytic uremic syndrome (HUS) (2). The infection correlates with ingestion of contaminated meat or vegetables, but it is also transmitted by water or even person-to-person contact (3,4).…”