E. coli Enteric Diseases Lawrence

Question 1

ETEC

Answer 1

• primarily a disease of calves and pigs

- Fimbriae are essential for colonization of small intestine

Question 2

ETEC Fimbrial types

Answer 2

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

Question 3

ETEC

Intestinal epithelial receptors for fimbriae

Answer 3

(F4, 5, 6, 18, 41)

Question 4

ETEC

Diarrhea results from action of enterotoxins

Answer 4

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

Question 5

ETEC Pathogenesis

Answer 5

i. ETEC adhere to enterocytes in small intestine, multiply, and secrete enterotoxin
ii. Diarrhea is watery with no blood

Question 6

ETEC

Host factors affecting disease include age (presence of fimbrial receptors), gastric pH, and specific antibodies

Answer 6

ETEC cause diarrhea in young cats, dogs, horses, and rabbits

Question 7

ETEC Diagnosis

Answer 7

i. Culture and serotype or demonstrate fimbriae by ELISA or agglutination
ii. Large numbers of E. coli in jejunum
iii. Adhered to intestinal epithelium

Question 8

ETEC Treatment and Prevention

Answer 8

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

Question 9

EAEC Pathogenesis

Answer 9

i. Adhere to intestine in an aggregative, stacked-brick pattern
1. Aggregative adherence fimbriae (AAF)
ii. Some express EAST1 toxin

Question 10

EAEC Diagnosis

Answer 10

i. “Gold standard” aggregative adherence to tissue culture cells

Question 11

EAEC Disease

Answer 11

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?

Question 12

EPEC Pathogenesis

Answer 12

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)

Question 13

EPEC Disease

Answer 13

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

Question 14

EPEC Diagnosis

Answer 14

i. Biopsy and detection of attached and effacing lesions

Question 15

EHEC/STEC (Shiga toxin E. coli)

pathogenesis

Answer 15

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

Question 16

EHEC/STEC (Shiga toxin E. coli)

disease in cattle

Answer 16

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

Question 17

AIEC

Answer 17

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

Question 18

Other E. coli diseases: Edema disease- weaned pigs (STEC)

Answer 18

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

Question 19

Other E. coli diseases: Extraintestinal pathogenic E. coli (ExPEC)

Answer 19

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

Question 20

Other E. coli diseases: Uropathogenic E. coli (UPEC)

Answer 20

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

Question 21

Other E. coli diseases: Avian pathogenic E. coli (APEC) – colibacillosis of fowl

Answer 21

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

Question 22

Other E. coli diseases: Pyometra

Answer 22

i. E. coli is the most common cause of pyometra in dogs and cats
ii. Adherence to endometrium – F1 fimbriae

Question 23

Other E. coli diseases: Mastitis

Answer 23

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

Question 24

Other E. coli diseases: Lab diagnosis

Answer 24

i. Routine culture and identification for septicemia, mastitis, pyometra, and UTI