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| − | {{review}}
| + | <big><center>[[Enterobacteriaceae|'''BACK TO ENTEROBACTERIACEAE''']]</center></big> |
| − | | + | <big><center>[[Bacteria|'''BACK TO BACTERIA''']]</center></big> |
| − | ===''Eschericia coli'' (''E. coli'') overview===
| + | <big><center>[[Infectious agents and parasites|'''BACK TO INFECTIOUS AGENTS AND PARASITES''']]</center></big> |
| − | [[File:Ecoli.jpg|200px|right]] | + | * Enterotoxigenic ''E.coli'' contributes to [[Intestines - Catarrhal Enteritis#Undifferentiated Neonatal Calf Diarrhoea|undifferentiated neonatal calf diarrhoea]], a mixed viral enteritis in calves. |
| − | *Member of ''Enterobacteriacae'' family of Gram-negative bacilli
| + | * [[Intestines - Catarrhal Enteritis#Colibacillosis|Colibacillosis]]. |
| − | *'''Facultative anaerobe'''
| + | * [[Intestines - Inflammatory Bowel Disease And Related Conditions#Histiocytic Ulcerative Colitis|Histiocytic ulcerative colitis]] in the dog and cat. |
| − | *One of predominant bacterial species in colonic flora
| + | * Causes [[Intestines - diarrhoea#Secretory Diarrhoeas|secretory diarrhoea]] |
| − | *Colonisation of intestinal tract from environmental sources shortly after birth
| + | * Causes [[Peritoneal cavity - inflammatory#In dogs|peritonitis in dogs]] and [[Peritoneal cavity - inflammatory#In pigs|peritonitis in pigs]] |
| − | *Abundant in the environment
| + | * In [[Bones - inflammatory#Osteomyelitis|osteomyelitis]] |
| − | *Most strains have low virulence
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| − | *Found in many non-specific, endogenous infections, eg. wound infections, upper respiratory tract infections, infections of the urinary tract, mammary glands and uterus and septicaemia
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| − | *An enteropathogen, causing neonatal diarrhoea in young animals and enteric colibacillosis
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| − | *Enterotoxigenic ''E. coli'' is the most common cause of diarrhoea in calves, lambs and pigs
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| − | *Pathogenic strains possess virulence factors allowing colonisation of mucosal surfaces
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| − | ===''E. coli'' characteristics===
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| − | | |
| − | *Usually motile with flagella and fimbriae
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| − | *'''Oxidase negative''' (do not possess cytochrome C oxidase)
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| − | *Grow on '''MacConkey agar''' (in presence of bile salts), producing pink colonies
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| − | *'''Haemolytic activity'' on blood agar characteristic of certain strains
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| − | *'''Lactose fermenter'''
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| − | *Reduce nitrates to nitrites and ferment glucose to produce acid and gas
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| − | *Possess a lipopolysaccharide ('''O''') antigen, a flagellate ('''H''') antigen, polysaccharide capsule ('''K''') antigens and fimbrial ('''F''') antigens
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| − | *Epidemiological typing of ''E. coli'' uses antigen combinations, eg. O125:K12:H42
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| − | ===Pathogenesis===
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| − | | |
| − | *<u>Virulence factors</u> include capsules, endotoxin, enterotoxins and colonisation factors
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| − | *Capsular polysaccharides produced by some strains prevent phagocytosis and interfere with complement
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| − | *Endotoxin is a lipolysaccharide component of the cell wall of Gram-negative bacteria, composed of lipid A, a core polysaccharide and various side chains
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| − | *'''Endotoxin''' is realeased when bacteria die, and causes endothelial damage leading to [[Disseminated Intravascular Coagulation|'''disseminated intravascular coagulation''']] and '''endotoxic shock'''; it is also a '''pyrogen'''
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| − | *Enterotoxins, verotoxins and cytotoxic necrotising factors produced by many pathogenic ''E. coli''; these produce cell damage at their site of action
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| − | *'''Alpha-haemolysin''' may increase iron availability for invading organisms
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| − | *'''Siderophores''' are made by certain pathogenic strains, and are responsible for iron aquisition; they include aerobactin and enterobactin
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| − | ==Extra-intestinal infection==
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| − | *Soft tissue infections in adult animals
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| − | *Pathogenesis:
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| − | **Produces an alpha-haemolysin which may be cytotoxic
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| − | **Iron aquisition system
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| − | **K antigens prevent phagocytosis or mimic host antigens and resist complement
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| − | **Fimbriae permit adhesion to mucosal surfaces
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| − | **May enter blood to cause septicaemia
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| − | *Clinical infections:
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| − | **'''Urogenital tract infections'''
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| − | ***Most common organism infecting urinary tract
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| − | ***Ascending infections of urinary tract
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| − | ***Causes pyometra in the dog and cat and [[Pyelonephritis|pyelonephritis]]
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| − | ***Cystitis in the bitch
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| − | ***Prostatitis in dogs via opportunistic infection
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| − | ***Colonisation of mucosa aided by fimbriae
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| − | **'''Mastitis'''
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| − | ***Opportunistic infection of mammary glands of sows and cows
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| − | ***Endotoxaemia in the acute form often fatal
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| − | ***Death within 24-48 hours during peracute disease
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| − | ***Animals depressed with sunken eyes
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| − | **[[Colibacillosis|'''Colibacillosis''']]:
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| − | ***Avian: | |
| − | ****Septicaemia in newly-hatched chickens
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| − | ****Infection enters via faecal contamination of the egg surface or via the ovary of the hen
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| − | ****Infection enters via the respiratory tract
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| − | ****A bacteraemia develops
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| − | ****Acute colisepticaemia, subacute fibrinopurulent serositis or chronic granulomatous disease of the viscera
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| − | ****Occurs in older birds via inhalation of ''E. coli'' in dust; respiratory infection spreads to the blood to cause acute colisepticaemia
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| − | ****Airsacculitis, pericarditis and perihepatitis during acute phase
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| − | ****Often secondary to virus or [[:Category:Mycoplasmas|''mycoplasma'']] infection or environmental stress
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| − | **'''Colisepticaemia''':
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| − | ***Systemic disease in young calves, piglets, foals, lambs
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| − | ***Penetration of intestinal mucosa and entrance into the blood
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| − | ***Invasive strains survive the host defences
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| − | ***Virulence related to adhesive properties, complement resistance and ability for iron aquisition
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| − | ***Ammonia, dust, viral infections and temperature changes enhance likelihood of disease
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| − | **[[Oedema Disease|'''Oedema disease of pigs''']]:
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| − | **'''Watery mouth of lambs''':
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| − | ***Affects lambs under three days old
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| − | ***Lack of colostrum allows collonisation and overgrowth of ''E. coli'' in the small intestine
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| − | ***Systemic invasion by ''E. coli''
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| − | ***Absorption of endotoxin leads to death
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| − | ***Severe depression, anorexia, salivation and abdominal distension
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| − | ***Morbidity and mortality high
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| − | ** [[Inflammatory Bowel Disease#Histiocytic Ulcerative Colitis|Histiocytic ulcerative colitis]] in the dog and cat.
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| − | ** Causes [[Peritonitis - Cats and Dogs|peritonitis in dogs]] and [[Peritonitis#In pigs|peritonitis in pigs]]
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| − | **Found in [[Osteomyelitis|osteomyelitis]] | |
| − | **Associated with neonatal [[Infectious Arthritis#In Cattle|polyarthritis of calves]]
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| − | **In [[Deep Pyoderma|deep pyoderma]]
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| − | **Found in [[Infectious Arthritis#In Horses|arthritis of horses]]
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| − | ==Intestinal infection==
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| − | *''E. coli'' is part of the flora of the large intestine, but is not usually found in the small intestine
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| − | *Some strains possess fimbrae which attach the bacteria to the small intestinal epithelium of particular animal species
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| − | *''E. coli'' may cause diarrhoea via attaching and effacing lesions, where bacteria adhere intimately to the enterocyte, and cause localised effacement of the brush border microvilli; the epithelial erosion causes [[Haemorrhage#Dysentery|dysentery]]
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| − | *'''Enterotoxigenic ''E. coli'' (ETEC)''':
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| − | **General:
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| − | *** Contributes to [[Calf Diarrhoea, Undifferentiated Neonatal|undifferentiated neonatal calf diarrhoea]], a mixed viral enteritis in calves, also known as enteric colibacillosis
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| − | ***Causes scours in pigs, calves and lambs
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| − | ***'Traveller's diarrhoea' in humans
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| − | **Pathogenesis:
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| − | ***Oral infection, intestinal colonisation and toxin production
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| − | ***Fimbrial antigen or colonisation factor antigens (CFAs)determine species specificity
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| − | ***Fimbrial adhesins allow bacteria to attach to mucosal surfacesin the small intestine and lower urinary tract; this prevents expulsion by peristalsis and flushing of urine
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| − | ***K88 (F4) is associated with adhesion to the small intestinal mucosa of pigs
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| − | ***K99 (F5) associated with adhesion in pigs and cattle (these fimbrial adhesins were originally thought to be capsular (K) antigens)
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| − | ***The '''fimbriae are encoded by plasmids'''
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| − | ***These strains carry a plasmid which encodes an enterotoxin
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| − | ***Two types of '''enterotoxin: heat-labile (LT) and heat-stable (ST) toxins'''
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| − | ***The '''plasmids''' which produce these toxins are '''responsible for the pathogenicity''' of these strains
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| − | ****'''LT'''
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| − | *****An oligometric toxin composed of an enzymatically-active A subunit (30KDa; 2 fragments - A1 and A2) and 5 identical B subunits (12KDa) forming the binding portion (B oligomer)
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| − | *****It attaches to the brush border of the epithelial cells of the small intestine
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| − | *****Causes ADP-ribosylation of the stimulatory subunit of guanine nucleotide binding proteins of the adenylate cyclase complex in eukaryotic cell membranes
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| − | *****This causes irreversible activation of adenylate cyclase in target cells
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| − | *****This raises the cAMP level and causes hypersecretion of water and chloride ions into the lumen of the small intestine and inhibits reabsorption of sodium
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| − | ****'''ST'''
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| − | *****Activates guanylate cyclase in enteric epithelial cells, stimulating fluid secretion
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| − | **Clinical signs:
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| − | ***The gut becomes distended with fluid and a [[Diarrhoea#Secretory Diarrhoeas|secretory diarrhoea]] which lasts several days results
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| − | ***Watery diarrhoea, dehydration, acidosis, death
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| − | **Immunity:
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| − | ***LT is antigenic
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| − | ***Immunity is developed via production of antibody to LT protein and fimbrial antigen
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| − | ***Parenteral vaccination of pigs and cattle protects offspring from scours via antibody production in the colostrum (passive immunity)
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| − | ***ST is not immunogenic; it is small, with only 19 amino acids
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| − | *'''Enteropathogenic ''E. coli'' (EPEC)''':
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| − | **Attaching and effacing strains of ''E. coli''
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| − | **Attach to small intestinal epithelial cells and cause necrosis of enterocytes and stunting and fusion of villi
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| − | **Possess ''E. coli'' adherence factor plasmid
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| − | **An adhesin, intimin is required for attachment to enterocytes
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| − | **Secrete signalling proteins that activate a tyrosine kinase, causing rearrangement of cytoskeletal proteins and effacement of microvilli
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| − | **Intracellular calcium levels increase and production of protein kinase C causes loss of chloride ions and water from the intestinal epithelial cells
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| − | **Diarrhoea results
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| − | *'''Enteroinvasive ''E. coli''''':
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| − | **Cause colisepticaemia in calves during their first week of life; occasionally in lambs, piglets and puppies
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| − | **Infection via ingestion or umbilicus; inadequate colostrum increases susceptibility
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| − | **Invade epithelial cells of small intestine by inducing endocytosis
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| − | **Traverse gut wall to lamina propria and enter lymphatics
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| − | **Resistant to complement-mediated killing
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| − | **Bacteraemia or septicaemia and endotoxaemia
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| − | **Widespread petechial haemorrhages of organs and serosa
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| − | **Abscesses, pneumonia in long term
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| − | **Death occurs in absense of treatment
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| − | *'''Enterohaemorrhagic ''E. coli''''':
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| − | **Possibly carried by cattle
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| − | **Produce shiga-like toxin, a vero toxin
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| − | **Plasmid-coded fimbriae important for virulence
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| − | **Intimin produced allowing intimate attachment to intestinal epithelial cells
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| − | **Strains do not product LT or ST and are not enteroinvasive
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| − | **Attaching and effacing lesions, unrelated to toxin production
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| − | **[[Disseminated Intravascular Coagulation|Disseminated intravascular coagulation]] and thrombus formation
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| − | **''E. coli'' O157:H7 causes haemorrhagic collitis-haemolytic uraemic syndrome in humans
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| − | *'''Cytotoxin necrotising factor-producing ''E. coli'''''
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| − | **Infrequently cause diarrhoea in calves, pigs and humans
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| − | **Important virulence factors include toxin and fimbriae
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| − | ==in cattle==
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| − | *Neonatal polyarthritis:
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| − | **[[Escherichia coli|'''''Coliforms''''']]
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| − | ***Localises in joints and meninges in severe non-fatal neonatal colibacillosis | |
| − | ***May remain as chronic arthritis in larger joints
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| − | [[Category:Enterobacteriaceae]] | |
| − | [[Category:To_Do_-_Bacteria]]
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