Escherichia coli
is a member of the family Enterobacteriaceae, and is a Gram-negative, facultative
anaerobic, non-sporulating rod, which is typically motile through peritrichous flagella.
E. coli exists as a commensal in the gut, but certain types of E. coli are harmful pathogens that can cause intestinal or extraintestinal infections.
Clinical symptoms of intestinal E. coli infection, which are transmitted through the faecal-oral route, include diarrhoea (bloody or non-bloody), fever, vomiting and abdominal cramps. More severely, infections with verocytotoxin-producing E. coli (VTEC/STEC) can develop into Haemolytic Uraemic Syndrome (HUS). Extraintestinal infections cover urinary tract infections, neonatal meningitis as well as infection of other anatomical sites.
STEC is not considered to be pathogenic in domestic animals. It is however, a relatively common gut commensal, particularly in cattle less than 2 years old, and livestock can therefore act as reservoirs for human infection.
Known host species
Samples used for detection of E. coli
- Faeces, urine, blood etc.
- Environmental samples
- Food
Genome
The E. coli genome consists of double-stranded DNA, and genome size varies from approximately 4.5 Mbp to 5.5 Mbp among isolates.
Nomenclature
The diarrhoeagenic E. coli are divided into several pathotypes: enteropathogenic E. coli (EPEC),
enterotoxigenic E. coli (ETEC), verocytotoxin-producing E. coli (VTEC) [or Shiga toxin-producing E. coli (STEC)]*, enteroinvasive E. coli (EIEC), enteroaggreative E. coli (EAEC) and diffusely adherent E. coli (DAEC).
*A subgroups of VTEC has been referred to as enterohaemorrhagic E. coli (EHEC)
.
Determination of the different pathotypes does not provide a high level of discriminatory power between strains. For this purpose, a vast number of methods are available for subtyping of E. coli. Most importantly, (O:H) serotyping is the gold standard for E. coli sub-typing, and several thousands of serotypes of E. coli are known, represented by 188 existing O-groups, and 53 H-types. Certain E. coli serotypes are known to be closely associated with specific disease, for instance the human infections with VTEC/STEC are typically associated with the O-Groups:
O157 (36.2%), O26 (8.1%), O104 (6.1%), O103 (5.7%), O145 (3.5%), O91 (3.2%), O63
(2.8%), O146 (2.4%), O117 (2.3%), O128 (1.2%), Orough (1.2%), O111 (1.2%), O76 (1%),
O125 (0.7%), and O5 (0.7%) (% of cases in EU, 2010-2012, ECDC).
Compare reference set
The E. coli reference set consists of 10 publically available genomes, which represents genomes of the most important VTEC/STEC O-groups: O157 (two genomes) O26, O104, O103, O145, O91, O146, O111, and one genome representing the non-pathogenic strain, MG1655-K12. (Genomes from strains with O groups O63 and O117 were not publically available at the time of reference database construction).
Further subtyping of the serovars was based on the MLST scheme developed by Wirth et al., 2006. MLST consists of sequencing of seven housekeeping genes, which are phylogenetically stable loci.
Last update: July 2015