Veterinary bacteriology: information about important bacteria
|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).
|Type Strain:||ATCC 11775 = CCUG 29300 = NCTC 9001.|
||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-|
|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:||
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.
||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.|
||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).
|Virulence Factors:||Strains of E. coli are divided into 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 (= 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.
|16S rRNA Seq.:|
||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|