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→Pathogenesis
{{review}}
===''Eschericia coli'' (''E. coli'') overview===
===''Eschericia coli'' (''E. coli'') overview===
[[File:Ecoli.jpg|200px|right]]
*Member of ''Enterobacteriacae'' family of Gram-negative bacilli
*Member of ''Enterobacteriacae'' family of Gram-negative bacilli
*'''Facultative anaerobe'''
*'''Facultative anaerobe'''
*Capsular polysaccharides produced by some strains prevent phagocytosis and interfere with complement
*Capsular polysaccharides produced by some strains prevent phagocytosis and interfere with complement
*Endotoxin is a lipolysaccharide component of the cell wall of Gram-negative bacteria, composed of lipid A, a core polysaccharide and various side chains
*Endotoxin is a lipolysaccharide component of the cell wall of Gram-negative bacteria, composed of lipid A, a core polysaccharide and various side chains
*'''Endotoxin''' is realeased when bacteria die, and causes endothelial damage leading to '''disseminated intravascular coagulation''' and e'''ndotoxic shock'''; it is also a '''pyrogen'''
*'''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'''
*Enterotoxins, verotoxins and cytotoxic necrotising factors produced by many pathogenic ''E. coli''; these produce cell damage at their site of action
*Enterotoxins, verotoxins and cytotoxic necrotising factors produced by many pathogenic ''E. coli''; these produce cell damage at their site of action
*'''Alpha-haemolysin''' may increase iron availability for invading organisms
*'''Alpha-haemolysin''' may increase iron availability for invading organisms
*'''Siderophores''' are made by certain pathogenic strains, and are responsible for iron aquisition; they include aerobactin and enterobactin
*'''Siderophores''' are made by certain pathogenic strains, and are responsible for iron aquisition; they include aerobactin and enterobactin
==Extra-intestinal infection==
==Extra-intestinal infection==
***Most common organism infecting urinary tract
***Most common organism infecting urinary tract
***Ascending infections of urinary tract
***Ascending infections of urinary tract
***Causes pyometra in the dog and cat and [[Kidney - Tubulointerstitial disease#Pyelonephritis|pyelonephritis]]
***Causes pyometra in the dog and cat and [[Pyelonephritis|pyelonephritis]]
***Cystitis in the bitch
***Cystitis in the bitch
***Prostatitis in dogs via opportunistic infection
***Prostatitis in dogs via opportunistic infection
***Death within 24-48 hours during peracute disease
***Death within 24-48 hours during peracute disease
***Animals depressed with sunken eyes
***Animals depressed with sunken eyes
**[[Intestines - Catarrhal Enteritis#Colibacillosis|'''Colibacillosis''']]:
**[[Colibacillosis|'''Colibacillosis''']]:
***Avian:
***Avian:
****Septicaemia in newly-hatched chickens
****Septicaemia in newly-hatched chickens
****Occurs in older birds via inhalation of ''E. coli'' in dust; respiratory infection spreads to the blood to cause acute colisepticaemia
****Occurs in older birds via inhalation of ''E. coli'' in dust; respiratory infection spreads to the blood to cause acute colisepticaemia
****Airsacculitis, pericarditis and perihepatitis during acute phase
****Airsacculitis, pericarditis and perihepatitis during acute phase
****Often secondary to virus or [[Mycoplasmas|''mycoplasma'']] infection or environmental stress
****Often secondary to virus or [[:Category:Mycoplasmas|''mycoplasma'']] infection or environmental stress
**'''Colisepticaemia''':
**'''Colisepticaemia''':
***Systemic disease in young calves, piglets, foals, lambs
***Systemic disease in young calves, piglets, foals, lambs
***Virulence related to adhesive properties, complement resistance and ability for iron aquisition
***Virulence related to adhesive properties, complement resistance and ability for iron aquisition
***Ammonia, dust, viral infections and temperature changes enhance likelihood of disease
***Ammonia, dust, viral infections and temperature changes enhance likelihood of disease
**[[Stomach and Abomasum - Inflammation#Oedema Disease In The Pig|'''Oedema disease of pigs''']]:
**[[Oedema Disease|'''Oedema disease of pigs''']]:
**'''Watery mouth of lambs''':
**'''Watery mouth of lambs''':
***Affects lambs under three days old
***Affects lambs under three days old
***Severe depression, anorexia, salivation and abdominal distension
***Severe depression, anorexia, salivation and abdominal distension
***Morbidity and mortality high
***Morbidity and mortality high
** [[Intestines - Inflammatory Bowel Disease And Related Conditions#Histiocytic Ulcerative Colitis|Histiocytic ulcerative colitis]] in the dog and cat.
** [[Inflammatory Bowel Disease#Histiocytic Ulcerative Colitis|Histiocytic ulcerative colitis]] in the dog and cat.
** Causes [[Peritoneal cavity - inflammatory#In dogs|peritonitis in dogs]] and [[Peritoneal cavity - inflammatory#In pigs|peritonitis in pigs]]
** Causes [[Peritonitis - Cats and Dogs|peritonitis in dogs]] and [[Peritonitis#In pigs|peritonitis in pigs]]
**Found in [[Bones - inflammatory#Osteomyelitis|osteomyelitis]]
**Found in [[Osteomyelitis|osteomyelitis]]
**Associated with neonatal [[Joints - inflammatory#In Cattle|polyarthritis of calves]]
**Associated with neonatal [[Infectious Arthritis#In Cattle|polyarthritis of calves]]
**Found in [[Joints - inflammatory#In Horses|arthritis of horses]]
**In [[Deep Pyoderma|deep pyoderma]]
**Found in [[Infectious Arthritis#In Horses|arthritis of horses]]
==Intestinal infection==
==Intestinal infection==
*''E. coli'' is part of the flora of the large intestine, but is not usually found in the small intestine
*''E. coli'' is part of the flora of the large intestine, but is not usually found in the small intestine
*Some strains possess fimbrae which attach the bacteria to the small intestinal epithelium of particular animal species
*Some strains possess fimbrae which attach the bacteria to the small intestinal epithelium of particular animal species
*''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 dysentery
*''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]]
*Enterotoxigenic ''E. coli'' (ETEC):
*'''Enterotoxigenic ''E. coli'' (ETEC)''':
**General:
**General:
*** Contributes to [[Intestines - Catarrhal Enteritis#Undifferentiated Neonatal Calf Diarrhoea|undifferentiated neonatal calf diarrhoea]], a mixed viral enteritis in calves, also known as enteric colibacillosis
*** Contributes to [[Calf Diarrhoea, Undifferentiated Neonatal|undifferentiated neonatal calf diarrhoea]], a mixed viral enteritis in calves, also known as enteric colibacillosis
***Causes scours in pigs, calves and lambs
***Causes scours in pigs, calves and lambs
***'Traveller's diarrhoea' in humans
***'Traveller's diarrhoea' in humans
***K88 (F4) is associated with adhesion to the small intestinal mucosa of pigs
***K88 (F4) is associated with adhesion to the small intestinal mucosa of pigs
***K99 (F5) associated with adhesion in pigs and cattle (these fimbrial adhesins were originally thought to be capsular (K) antigens)
***K99 (F5) associated with adhesion in pigs and cattle (these fimbrial adhesins were originally thought to be capsular (K) antigens)
***The fimbriae are encoded by plasmids
***The '''fimbriae are encoded by plasmids'''
***These strains carry a plasmid which encodes an enterotoxin
***These strains carry a plasmid which encodes an enterotoxin
***Two types of enterotoxin: heat-labile (LT) and heat-stable (ST) toxins
***Two types of '''enterotoxin: heat-labile (LT) and heat-stable (ST) toxins'''
***The plasmids which produce these toxins are responsible for the pathogenicity of these strains
***The '''plasmids''' which produce these toxins are '''responsible for the pathogenicity''' of these strains
***LT is 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)
****'''LT'''
***It attaches to the brush border of the epithelial cells of the small intestine
*****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)
***LT causes ADP-ribosylation of the stimulatory subunit of guanine nucleotide binding proteins of the adenylate cyclase complex in eukaryotic cell membranes
*****It attaches to the brush border of the epithelial cells of the small intestine
***This causes irreversible activation of adenylate cyclase in target cells
*****Causes ADP-ribosylation of the stimulatory subunit of guanine nucleotide binding proteins of the adenylate cyclase complex in eukaryotic cell membranes
***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
*****This causes irreversible activation of adenylate cyclase in target cells
***ST activates guanylate cyclase in enteric epithelial cells, stimulating fluid secretion
*****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
****'''ST'''
*****Activates guanylate cyclase in enteric epithelial cells, stimulating fluid secretion
**Clinical signs:
**Clinical signs:
***The gut becomes distended with fluid and a [[Intestines - diarrhoea#Secretory Diarrhoeas|secretory diarrhoea]] which lasts several days results
***The gut becomes distended with fluid and a [[Diarrhoea#Secretory Diarrhoeas|secretory diarrhoea]] which lasts several days results
***Watery diarrhoea, dehydration, acidosis, death
***Watery diarrhoea, dehydration, acidosis, death
**Immunuty:
**Immunity:
***LT is antigenic
***LT is antigenic
***Immunity is developed via production of antibody to LT protein and fimbrial antigen
***Immunity is developed via production of antibody to LT protein and fimbrial antigen
***Parenteral vaccination of pigs and cattle protects offspring from scours via antibody production in the colostrum (passive immunity)
***Parenteral vaccination of pigs and cattle protects offspring from scours via antibody production in the colostrum (passive immunity)
***ST is not immunogenic; it is small, with only 19 amino acids
***ST is not immunogenic; it is small, with only 19 amino acids
*Enteropathogenic ''E. coli'' (EPEC):
**Attching and effacing strains of ''E. coli''
*'''Enteropathogenic ''E. coli'' (EPEC)''':
**Attaching and effacing strains of ''E. coli''
**Attach to small intestinal epithelial cells and cause necrosis of enterocytes and stunting and fusion of villi
**Attach to small intestinal epithelial cells and cause necrosis of enterocytes and stunting and fusion of villi
**Possess ''E. coli'' adherence factor plasmid
**Possess ''E. coli'' adherence factor plasmid
**Intracellular calcium levels increase and production of protein kinase C causes loss of chloride ions and water from the intestinal epithelial cells
**Intracellular calcium levels increase and production of protein kinase C causes loss of chloride ions and water from the intestinal epithelial cells
**Diarrhoea results
**Diarrhoea results
*Enteroinvasive ''E. coli'':
*'''Enteroinvasive ''E. coli''''':
**Cause colisepticaemia in calves during their first week of life; occasionally in lambs, piglets and puppies
**Cause colisepticaemia in calves during their first week of life; occasionally in lambs, piglets and puppies
**Infection via ingestion or umbilicus; inadequate colostrum increases susceptibility
**Infection via ingestion or umbilicus; inadequate colostrum increases susceptibility
**Abscesses, pneumonia in long term
**Abscesses, pneumonia in long term
**Death occurs in absense of treatment
**Death occurs in absense of treatment
*Enterohaemorrhagic ''E. coli'':
*'''Enterohaemorrhagic ''E. coli''''':
**Possibly carried by cattle
**Possibly carried by cattle
**Produce shiga-like toxin, a vero toxin
**Produce shiga-like toxin, a vero toxin
**Plasmid-coded fimbriae important for virulence
**Plasmid-coded fimbriae important for virulence
**Intimin produced allowing intimate attchment to intestinal epithelial cells
**Intimin produced allowing intimate attachment to intestinal epithelial cells
**Strains do not product LT or ST and are not enteroinvasive
**Strains do not product LT or ST and are not enteroinvasive
**Attaching and effacing lesions, unrelated to toxin production
**Attaching and effacing lesions, unrelated to toxin production
**Disseminated intravascular coagulation and thrombus formation
**[[Disseminated Intravascular Coagulation|Disseminated intravascular coagulation]] and thrombus formation
**''E. coli'' O157:H7 causes haemorrhagic collitis-haemolytic uraemic syndrome in humans
**''E. coli'' O157:H7 causes haemorrhagic collitis-haemolytic uraemic syndrome in humans
*Cytotoxin necrotising factor-producing ''E. coli''
*'''Cytotoxin necrotising factor-producing ''E. coli'''''
**Infrequently cause diarrhoea in calves, pigs and humans
**Infrequently cause diarrhoea in calves, pigs and humans
**Important virulence factors include toxin and fimbriae
**Important virulence factors include toxin and fimbriae
==in cattle==
*Neonatal polyarthritis:
**[[Escherichia coli|'''''Coliforms''''']]
***Localises in joints and meninges in severe non-fatal neonatal colibacillosis
***May remain as chronic arthritis in larger joints
[[Category:Enterobacteriaceae]]
[[Category:To_Do_-_Bacteria]]