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Phylum	Class	Order	Family	Genus	Species/Subspecies

Species/Subspecies:

Escherichia coli

Categories:

Zoonotic; causes hemolysis; motile; notifiable diseases and bacteria

Etymology:

Genus name: named after the German pediatrician Theodor Escherich, who first isolated the type species of the genus.
Species epithet: from the large intestine (colon).

Significance:

[Very important]

Taxonomy:

Phylum
Pseudomonadota

Class
Gammaproteobacteria

Order
Enterobacterales

Family
Enterobacteriaceae

Genus
Escherichia

Type Strain:

ATCC 11775 = CCUG 29300 = NCTC 9001.

Macromorphology (smell):

Medium sized (2-3 mm in diameter), opaque, sticky and greyish white colonies. Some strains give a narrow clear hemolysis zone on blood agar. Characteristic odor.

Micromorphology:

Short motile rods (0.5 x 1-3 µm). E. coli is peritrichous, i.e. has flagella over the whole surface.

Gram +/Gram -:

G-

Metabolism:

Facultatively anaerobic.

Catalase/Oxidase:

+/-

Other Enzymes:

DNase -, β-glucoronidase + (cf. Klebsiella spp.), esculinase V, ornithine decarboxylase V, tryptophanase + (= indol +), urease -.

Biochemical Tests:

Citrate -, hydrogen sulphide (H₂S) -, methyl red +, Voges-Proskauer -.

Fermentation of carbohydrates:

D-glucose
+

lactose
+

maltose
+

L-rhamnose
(+)

sucrose
v

L-arabinose
+

cellobiose
-

D-mannitol
+

salicin
v

trehalose
+

glycerol
(+)

inulin
?

raffinose
v

D-sorbitol
+

starch
?

Both gas and acid are formed by those carbohydrates that are fermentable. There are biochemically inactive strains, which do not ferment some of the above carbohydrates.

Microbiological tests:

Motility test is sometimes performed to confirm suspected findings of E. coli.

Spec. Char.:

Some strains of E. coli can form a polysaccharide capsule and around 80 different K antigen types have been identified, thus representing different variants of polysaccharides in the capsule.

Special Media:

BG medium is used to distinguish between E. coli and Salmonella spp. Chromogenic E. coli/coliform selective agar is used for enumeration of coliform bacteria. Dip slides (e.g. UriCult) is used to analyze urine from patients with suspected urinary tract infections.

SELMA- or SELMA Plus plates are used for cultivation of milk samples when mastitis is suspected.

Disease:

Different pathotypes cause various diseases (enteric, septicaemic and others).

Hosts	Pathotype	Disease	Clinical picture
All animal species including humans	UPEC, Uropathogenic E. coli	Urinary Tract infection (UTI),	Cystitis, Bacteriuria occurs with >100 000 CFU/ml urine and UVI if >100 000 CFU/ml and symptoms of disease. Most common bacterial cause of UTI regardless of animal species
Pigs	ETEC (Enterotoxic E. coli), VTEC, (Verotoxic E. coli)	ETEC Neonatal diarrhea Colisepticaemia Piglet meningitis Weanling diarrhea Mastitis Mastitis-metritis VTEC *Oedema disease	ETEC Piglets <1 week, profuse watery diarrhea, dehydration and high mortality Piglets, occasionallly septicaemia, death within 48h Acute meningitis and fibrinous polyserosit Pigs 2 weeks after weaning, diarrhea, anorexia and fever, mortality lower than neonatals Sows, one or more mammary gland affected Inflammation in the uterus and udder VTEC *Oedema in head, weaned pigs, sudden death,ataxia, convulsions and paralysis
Poultry	APEC (Avian pathogenic E. coli)	Colisepticaemia, omphalitis (young chicks), airsacculitis, pneumoni, pericarditis, perihepatitis,Yolk sac infection, salpingitis	Sporadic disease/death or as outbreaks with sudden high mortality. Septicaemia and infection in several different organs such as the air sacs, lungs, pericardium, salpingitis.
Cattle	VTEC, (Verotoxic E. coli)	Colibacillosis, "white scours" Joint ill Colisepticaemia Coliform mastitis	Young calves (<1 week), fluid faeces, white pasty faeces around rectum, dehydration, high mortality Young calves (<1 week) peracute, fever, anorexia, depression. Death due to endotoxic shock Calves, arthritis, calves surviving colisepticaemia Peracute, fever, anorexia, depression. Death due to endotoxic shock
Sheep	EPEC (Enteropathogenic E. coli) STEC	Haemorrhagic diarrhoea Watery mouth Mastitis	EPEC, lamb, haemorrhagic diarrhea possibly bloody in young animals Lamb, anorectic, saliva drools, abdominal tympany, splashing sound in abomasum, death within a day Ewes, mastitis
Dog	EPEC (Enteropathogenic E. coli)	Colisepticaemia (puppies) Pyometritis (bitches)	EPEC, neonatal pups, septicaemia, often fatal Uterine inflammation, discharge, fever, increased thirst
Horse (foals)	SEPEC, (Septicaemic E. coli)	Colisepticaemia	Septicaemia, fatal pneumonia
Humans	ETEC (Enterotoxic E. coli) EPEC (Enteropathogenic E. coli) EHEC(Enteroenterohemorrhagic E. coli)	Food poisoning	ETEC, tourist diarrhea, profuse watery diarrhea EPEC, mainly affects young children in low-income countries EHEC, diarrhea (bloody), HUS (Haemolytic Uremic Syndrome) affect mostly children

Virulence Factors:

Strains of E. coli are divided intoÂ different pathotypes depending on their virulence factors. Some human patotypes and their virulence factors are listed below:

EPEC, enteropathogenic E. coli, type III secretion system (intimin, Tir, EspA, B, D och F) etc.
ETEC, enterotoxigenic E. coli, colonization factor antigens (CFAs), heat labile and heat stabile toxins (LT and STa, STB, respectively).
VTEC (= STEC), verotoxin producing E.coli, verotoxin.
EHEC, enterohemorragic E. coli, type III secretion system, Verotoxins (VT1 and VT2) etc.
EIEC, enteroinvasive E. coli, invasion plasmid (pINV).
EAggEC (=Â EAEC), enteroaggregativ E. coli, aggregativa adhesion fimbriae (AAFs), AEAC flagellin and toxins.
UPEC, uropathogenic E. coli, adhesion factors (F1C, S, M and Dr), P fimbriae, cytotoxic necrotizing factor (CNF-1), hemolysin (HlyA), autotransported protease (Sat) and type I secretion system.
NMEC, neonatal meningitis/sepsis-associated E. coli, outer membrane proteins (OmpA, IbA, IbeB, IbeC and AsIA), cytotoxic necrotizing factor (CNF-1) and capsule (K1).

Note that Shigatoxin is used synonymously with Verotoxin and the toxins are accordingly termed Stx1 and Stx2.

Genome Sequence:

Acc-no	Strain	Size (bp)	Genome
AC_000091	K12-W3110	4 646 332	1c + 0

Thirty-two strains have been sequenced including NC_002695, Stam O157:H7, 5 498 450 bp. These strains have up to 5 circular plasmids.

16S rRNA Seq.:

Acc-no	Strain	Number of NT	Operon
X80725	(T)	1450	7

Taxonomy/phylogeny:

Six species have been described within genus Escherichia. E. coli belongs to the family Enterobacteriaceae and is very closely related to members of the genus Shigella. In fact, E. coli and members of genus Shigella form a monophyletic cluster (see Fig. 68:14 to the left), which shows that phylogenetically, they belong to the same species. E. coli is also closely related to members of the genus Salmonella.

Legislation:

E. coli, stam O157:H7, belongs to category B as a potential bioterrorism agent according to NIAID.

Comment:

Type species for the genus. Most strains of E. coli are usually non-pathogenic intestinal bacteria, which belong to the normal flora, but some strains are pathogenic. Infections with verotoxin producing strains (VTEC) may be notifyable in Sweden.

Reference(s):

No. 17, 40, 99, 124

Updated:

2023-10-19

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