Escherichia coli bacteria

Escherichia coli

Escherichia coli picture gram negative rods drawing

Four different strains of Escherichia coli on Endo agar with biochemical slope (see here). Glucose fermentation with gas production, urea and H2S negative, lactose positive (with exception of strain D - "late lactose fermenter"; on Endo agar it looks like lactose negative). All four strains are mannitol positive (best seen in fig. D), cellobiose negative (strains A, B). Approximately 50% of E.coli strains are sucrose negative (fig.A, D). Colonies of some strains have typical greenish metallic sheen (fig.E) but many of them grow without it (fig.F).

Escherichia coli (commonly abbreviated E. coli) is a Gram-negative, rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms (endotherms). Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in humans. The harmless strains are part of the normal flora of the gut, and can benefit their hosts by producing vitamin K2, and by preventing the establishment of pathogenic bacteria within the intestine. E. coli and related bacteria constitute about 0.1% of gut flora, and fecal-oral transmission is the major route through which pathogenic strains of the bacterium cause disease.

Gastrointestinal infection
Certain strains of E. coli, such as O157:H7, O104:H4, O121, O26, O103, O111, O145,and O104:H21, produce potentially lethal toxins. Food poisoning caused by E. coli can result from eating unwashed vegetables or undercooked meat. O157:H7 is also notorious for causing serious and even life-threatening complications such as hemolytic-uremic syndrome. The O104:H4 strain is equally virulent. It is the strain behind the deadly June 2011 E. coli outbreak in Europe.

Enteric E. coli (EC) are classified on the basis of serological characteristics and virulence properties:

  • Enterotoxigenic E. coli (ETEC)
  • Enteropathogenic E. coli (EPEC)
  • Enteroinvasive E. coli (EIEC)
  • Enterohemorrhagic E. coli (EHEC)
  • Enteroaggregative E. coli (EAEC)

Abbreviated from Wikipedia.

Urinary tract infection
Uropathogenic E. coli (UPEC) is responsible for approximately 90% of urinary tract infections (UTI) seen in individuals with ordinary anatomy. In ascending infections, fecal bacteria colonize the urethra and spread up the urinary tract to the bladder as well as to the kidneys (causing pyelonephritis), or the prostate in males. Because women have a shorter urethra than men, they are 14 times more likely to suffer from an ascending UTI. Uropathogenic E. coli use P fimbriae (pyelonephritis-associated pili) to bind urinary tract endothelial cells and colonize the bladder. Uropathogenic E. coli produce alpha- and beta-hemolysins, which cause lysis of urinary tract cells.

Neonatal meningitis
It is produced by a serotype of Escherichia coli that contains a capsular antigen called K1. The colonisation of the newborn's intestines with these strains, that are present in the mother's vagina, lead to bacteraemia, which leads to meningitis. And because of the absence of the IgM antibodies from the mother (these do not cross the placenta because FcRn only mediates the transfer of IgG), plus the fact that the body recognises as self the K1 antigen, as it resembles the cerebral glicopeptides, this leads to a severe meningitis in the neonates.

Wikipedia.

Escherichia coli basic characteristics

  • GRAM-NEGATIVE RODS
  • MOTILE
  • NON-SPORE-FORMING
  • CATALASE: POSITIVE
  • OXIDASE: NEGATIVE
  • FACULTATIVELY ANAEROBIC

Escherichia coli biochemical identification

MacConkey
growth
Indole
production
Methyl
red
Voges-
Proskauer
Citrate
(Simmons)
Hydrogen
sulfide(TSI)
Urea
hydrol.
Lysine
decarb.
Arginine
dihydrol.
Ornithine
decarb.
POS. POS. POS. NEG. NEG. NEG. NEG. POS. d D
Motility
(36 °C)
D-glucose
acid/gas
D-mannitol
ferm.
Sucrose
ferm.
Lactose
ferm.
D-sorbitol
ferm.
Cellobiose Esculin
hydrol.
Acetate
utiliz.
ONPG test
POS. POS./POS. POS. D POS. POS. NEG. NEG. D POS.