E. coli Enteric Diseases Lawrence Flashcards
ETEC
- primarily a disease of calves and pigs
- Fimbriae are essential for colonization of small intestine
ETEC Fimbrial types
i. F4 – expressed on swine ETEC
ii. F5 – found on cattle, sheep, and swine ETEC
iii. F6 – almost always associated with swine ETEC, sometimes cattle
iv. F18 – common fibrial adhesion; associated with swine ETEC
v. F41 – usually on cattle ETEC, sometimes swine
ETEC
Intestinal epithelial receptors for fimbriae
(F4, 5, 6, 18, 41)
ETEC
Diarrhea results from action of enterotoxins
i. Heat-labile (LT) produced by human and porcine strains
ii. It causes dysregulation of adenylate cyclase, which causes overproduction of cAMP
iii. Two types of LT:
1. LT1 – neutralized by anti-cholera toxin antibodies
2. LT2 – not neutralized
ETEC Pathogenesis
i. ETEC adhere to enterocytes in small intestine, multiply, and secrete enterotoxin
ii. Diarrhea is watery with no blood
ETEC
Host factors affecting disease include age (presence of fimbrial receptors), gastric pH, and specific antibodies
ETEC cause diarrhea in young cats, dogs, horses, and rabbits
ETEC Diagnosis
i. Culture and serotype or demonstrate fimbriae by ELISA or agglutination
ii. Large numbers of E. coli in jejunum
iii. Adhered to intestinal epithelium
ETEC Treatment and Prevention
i. Fluid therapy, oral antibiotics
ii. Prevention: good husbandry
iii. Vaccines administered parenterally to sows and cows
iv. Anti-fimbrial antibodies administered orally to piglets
EAEC Pathogenesis
i. Adhere to intestine in an aggregative, stacked-brick pattern
1. Aggregative adherence fimbriae (AAF)
ii. Some express EAST1 toxin
EAEC Diagnosis
i. “Gold standard” aggregative adherence to tissue culture cells
EAEC Disease
i. Persistent diarrhea in children and adults
ii. Strains with EAST1 or AAF can be isolated from weaned pigs and calves with diarrhea
1. Causation not established?
EPEC Pathogenesis
i. Bundle forming pili (BFP) are important for initial binding to intestinal cells
ii. Only a small fraction causing infection in pigs, calves, dogs, and cats produce BFP
iii. Intimate adherence is by intimin
iv. Type III secretion system
1. Tir
v. Pedestal structures are formed that bacteria attach to
vi. Some injected proteins dysregulate chloride transport (and sodium)
EPEC Disease
i. Watery diarrhea and disruption of electrolyte balance
ii. EPEC cause diarrhea in all animal species, including humans
iii. Major cause of diarrhea in young rabbits
EPEC Diagnosis
i. Biopsy and detection of attached and effacing lesions
EHEC/STEC (Shiga toxin E. coli)
pathogenesis
i. Similar to EPEC; AE lesions – target large intestine cells
ii. Produce Shiga toxin (Stx) unlike EPEC
1. Type of AB toxin
2. Inhibition of protein synthesis leading to cell death
3. Two types: Stx1 and Stx2
4. Carried by lysogenic bacteriophages
iii. Diarrhea is caused by the same mechanism as EPEC, as well as damage to endothelial cells
EHEC/STEC (Shiga toxin E. coli)
disease in cattle
i. Neonatal and infant calves (peak at 4-5 weeks)
ii. Low mortality rate; decreased growth rate
iii. Localized and diffuse hemorrhages in the large intestine
iv. Carrier state in adults and calves; risk to human health
AIEC
a. Significantly associated with Crohn’s disease in humans
b. Good evidence for etiologic role in dogs with histiocytic ulcerative colitis
c. Adhere to and invade enterocytes
d. Invade macrophages under the epithelial layer and multiply in vacuoles
Other E. coli diseases: Edema disease- weaned pigs (STEC)
i. Caused by Stx2e
ii. F18ab fimbriae
iii. Disease is characterized by neurological signs and edema
iv. Sudden death can occur
v. Diagnosis
1. Detection of Stx genes
Other E. coli diseases: Extraintestinal pathogenic E. coli (ExPEC)
i. Can occur in cattle, swine, and horses
ii. Primarily as a result of failure of passive transfer
iii. Invasion can occur through digestion, improperly treated umbilicus, or conjunctivae
iv. Pathogenesis
1. Fimbrial adhesin F17c
2. Endotoxemia can result in death
v. Virulence factors
1. ExPEC often have Vir plasmid
2. Capsule (K1 type) and outer membrane proteins
3. Often produce alpha-hemolysin
4. Clinical signs: fever, depression, sometimes polyarthritis, meningitis, and bronchopneumonia
Other E. coli diseases: Uropathogenic E. coli (UPEC)
i. UPEC can cause urethritis, cystitis, ureteritis, prostatitis, and pyelonephritis
ii. E. coliis the most frequent cause of UTI in dogs, cats, and people
iii. Often transient members of the normal intestinal flora
iv. P fimbriae that bind receptors in the bladder epithelium
Other E. coli diseases: Avian pathogenic E. coli (APEC) – colibacillosis of fowl
i. Pathogenesis
1. APEC cause aerosacculitis, polyserositis, and septicemia in chickens, turkeys, and other avian species
2. APEC are found in the intestinal microflora of healthy birds
3. Disease often secondary to environmental factors
4. Eggs can be infected; can cause embryonic death
5. Genetic similarities between APEC strains and human ExPEC strains cause concern that poultry serve as a reservoir for zoonotic infections
ii. Virulence factors
1. F1 (respiratory tract) and P (internal organs) fimbriae
2. Iron sequestering system
3. K1 capsule
4. Hemin uptake system
iii. Disease
1. Air-exchange regions of the lung and the airsacs are important sites of entry into the bloodstream during infection
2. Cause septicemia, resulting in massive lesions
3. Sudden death
4. Can also cause chronic disease with debilitation, diarrhea, and respiratory distress
Other E. coli diseases: Pyometra
i. E. coli is the most common cause of pyometra in dogs and cats
ii. Adherence to endometrium – F1 fimbriae
Other E. coli diseases: Mastitis
i. Along with Klebsiella and Enterobacter, E.coli causes coliform mastitis
1. Highly fatal peracute form of mastitis septicemia
2. Can cause gangrenous mastitis in cows and agalactia in sows (quickly if not treated)
3. Good husbandry and management important for control and prevention
Other E. coli diseases: Lab diagnosis
i. Routine culture and identification for septicemia, mastitis, pyometra, and UTI
