5.5 Gram negative aerobes 1

Question 1

Main characteristics Enterobacterales: type, habitat, motility, fermentation, agar

Answer 1

• Gram negative rods
• Aerobes or facultative anaerobes
• Mostly live in the intestines
• Most have motility (flagella)
• Lactose fermenters vs non-lactose fermenters
• Grow on MacConkey agar

Question 2

major opportunistic pathogens associated with multidrug resistance in the enterobacterales order

Answer 2

Klebsiella pneumoniae, Enterobacter

Question 3

How is E. coli classified?

Answer 3

Pathotypes: based on the ability to produce virulence factors and ability to cause disease
>Sub-sets of clones differentiated by their ability to cause disease
>EPEC, STEC, ETEC, ExPEC

Serotypes: classified based on antigenic composition

Question 4

why is it important to classify E. coli?

Answer 4

Differentiate commensal vs. pathogenic E. coli

Question 5

what is multidrug resistance?

Answer 5

resistance to 3 or more drugs

Question 6

E Coli serotypes/ virulence factors

Answer 6

classified based on antigenic composition
* Capsule (K)
* LPS (O)
* Fimbriae (F)
* Flagella (H)
*eg. O157: H7

Question 7

how is pathogenic E coli classified?

Answer 7

Intestinal Pathogenic:
EPEC - Enteropathogenic E. Coli
STEC/EHEC - Enterohaemorrhagic
ETEC - Enterotoxigenic

Extraintestinal Pathogenic:
APEC - Avian pathogenic
UPEC - uropathogenic

Question 8

ecology of the pathogenic E coliand most important route of transmission:

Answer 8

Most important route: Fecal – oral

-contamination of environment, wildlife, water, and agriculture
-Transmission between production animals
-Transmission animal to person (farms, abattoirs, markets, etc.)
-Transmission person to person and between person and domestic animals
-transmission food and water to person

Question 9

What is ETEC? what are its symptoms in various species?

Answer 9

EnteroToxigenic E. coli

• Neonatal diarrhea: piglets and calves (can also affect goats, sheep)
  >Neonatal diarrhea (scour) Calve 0-1 week
• Post-weaning diarrhea (4-8 weeks): pigs
• Dog : diarrhea in young animals
• Severe, may die within hours/days

Question 10

what are the virulence factors of ETEC? what are the enterotoxins?

Answer 10

ETEC: EnteroToxigenic E. coli

• Virulence factors
  -Fimbriae/pili (adherence)
• Enterotoxins:
  LT: Heat-Labile Toxin (pigs)
  STa: Heat-Stable Toxin (pigs, calves, dogs)
  STb: Heat-Stable Toxin (pigs)

Question 11

lesions caused by ETEC

Answer 11

No histological lesions: only action of toxins Macro: fluid in the small intestines

Question 12

pathegenesis of ETEC

Answer 12

EnteroToxigenic E. coli

1. ingestion of ETEC
2. Colonization of jejenum and ileum
   >electrolyte imbalance, “biochemical reaction”, irreversible
3. water and electrolytes exit cells
4. diarrhea and weight loss

Question 13

The action of heat-label and heat-stable toxins produced by ETEC cause destruction of the microvilli of intestinal epithelial cells and lead to diarrhea in calves.
a) Correct
b) Incorrect
Why?

Answer 13

Incorrect - they do not destroy microvilli. There is merely a biochemical reaction

Question 14

what does EPEC stand for? what symptoms does it cause is rabbits, dogs, pigs, cows?

Answer 14

• Rabbits: newborn and weaning diarrhea (sometimes with blood)
  – Where: +++ large intestine and +small intestines
• Dogs: diarrhea in young animals
  – Where: small and large intestines
• Pigs: postweaning diarrhea
  – Where: small intestines
• Cattle: hemorrhagic dysentery
• Where: colon

Question 15

EPEC invasion strategy? What are its virulence factors?

Answer 15

EnteroPathogenic

makes a pedestal and has a syringe-like apparatus

Virulence factors:
-Intimin (adhesin)
-Tir (Intimin-receptor)
-EspA, EspB, EspD, EspC (enterotoxins)

Question 16

How does EPEC cause disease?

Answer 16

1. ingestion
2. colonization of small and large intestine
3. Attachment to epithelial cells, and effacement of microvilli
4. diarrhea

Question 17

What is STEC? what is its toxin and what does it do? how is it related to EHEC?

Answer 17

STEC: Shiga Toxin producing E. coli

• What is Shiga-Toxin?
  Stx1 and Stx2 are major groups
  Ingestion cause diarrhea and damage in the vascular endothelium
  =verotoxin = shiga-like toxin = shiga toxin
• EHEC (Enterohemorrhagic E. coli): diarrhea and systemic disease, can lead to hemolytic uremic syndrome (HUS) in humans
  Serotype: O157:H7

Question 18

what does STEC cause in pigs

Answer 18

edema disease, in the small intestines

Question 19

what disease does it cause and how does STEC cause disease in pigs? what are the virulence factors and toxins?

Answer 19

causes edema disease in pigs

1. ingestion
2. colonization of jejenum and ileum
3. transport of toxin to circulation
   >It opens the tight junctions of endothelial cells=> leakage of plasma
4. Edema, ataxia, death

• Virulence factors: Fimbriae/pilli: F18
• Toxin: Stx2e (Shiga-toxin)

This STEC is highly transmissible!

Question 20

what is UPEC? what kind of disease does it cause, and what is the basic pathogenesis? what are its virulence factors?

Answer 20

UPEC: UroPathogenic E. coli
-Extraintestinal

• Most common UTI pathogen in small animals
• Origin: fecal, ascending infection

> neutrophils are recruited to kill UPEC but also damage epithelial cells
-cytotoxins produced by UPEC cause further tissue damage

Virulence factors:
- Fimbriae (pili/adhesins)
- LPS
- Siderophores (iron scavenging)
- Capsule (antiphagocytic)
* Recurrent infections: E. coli may invade uroepithelial cells (persistence, protection)

Question 21

Overall summary of pathogenic species of ExpEC and what they do

Answer 21

Extraintestinal E Coli

Uropathogenic E. coli: UTIs

Avian Pathogenic E. coli:
Systemic and localized Opportunitistic infections Mastitis, pyometra etc