E. coli

Question 1

True or False:

Of the genus Escherichia, there are a number of species known to be clinically relevant.

Answer 1

False. Of the genus Escherichia, there are a number of species, but Escherichia coli is the only clinically relevant species known.

Question 2

Define serotype.

Answer 2

Serotype: complete antigenic formula of an organism

Question 3

What are the four antigenic variables used in serotyping and what do they describe?

Answer 3

The four antigenic variables used in serotyping are:
O - O antigen
H - Flagella
F - Fimbriae
K - Capsule

Question 4

Which of the four antigenic variables is involved in bacterial adhesion?

Answer 4

Fimbriae (F) are involved in adhesion. Non-fimbrial adhesins also play a role in adhesion, but they are used in serotyping.

Question 5

True or False:

All E. coli present in an animal are pathogenic.

Answer 5

False. E. coli are a very diverse species with many different serotypes, most of which are commensal.

Question 6

True or False:

Domestic animals do not develop shigellosis.

Answer 6

True. Shigella spp. are only present in humans, so domestic animals do not develop shigellosis.

Question 7

What does it mean if a strain of E. coli is an obligate pathogen?

Answer 7

The pathogenicity of E. coli is strain-dependent. If the strain is an obligate pathogen then it is also age-dependent.

Question 8

How do we identify pathogenic types of avian E. coli?

Answer 8

Avian pathogenic E. coli (APEC) are identified by their O antigens, where O: 1, 2, 78 indicate pathogenic strains.

Question 9

What type(s) of pathogenic E. coli utilize serotyping and biotyping for identification?

Answer 9

Rabbit pathogenic E. coli (RPEC) are identified using serotyping and biotyping.

Question 10

What is bacterial lipopolysaccharide associated with on the cell?

Answer 10

Lipopolysaccharide (LPS) is associated with the bacterial cell wall.

Question 11

What are the two categories of virulence factors?

Answer 11

Virulence factors are categorized as either cell-associated or extracellular.

Question 12

True or False:

Extracellular virulence factors of E. coli are secreted from the bacteria.

Answer 12

True.

Question 13

What are siderophores?

Answer 13

Siderophores are iron-sequestering molecules that deliver iron to the bacteria to enhance growth.

Question 14

What are the five enteric pathotypes of E. coli that occur in domestic species?

Answer 14

The five enteric pathotypes of E. coli that occur in domestic species include:

1. Enterotoxigenic (ETEC)
2. Enterohemorrhagic (EHEC)
3. Verotoxigenic (VTEC)/Shiga-like toxic (STEC)
4. Enteropathogenic (EPEC)
5. Rabbit pathogenic (RPEC)

Question 15

True or False:

E. coli does not cause diarrhea in adult pigs.

Answer 15

True. E. coli is an obligate pathogen in pigs, meaning it is age-dependent. E. coli cause diarrhea in piglets and does not cause diarrhea in adult pigs.

Question 16

ETEC causes diarrhea in piglets of what age groups?

Answer 16

Enterotoxigenic E. coli (ETEC) causes watery diarrhea in neonates, piglets between 2 and 4 weeks of age, and weanlings.

Question 17

What factors cause disease in a piglet with an ETEC infection? Why are they important?

Answer 17

The adhesion factors and the enterotoxins are the factors causing disease. They are important because you can vaccinate for them.

Question 18

What are the adhesion factors found in serotypes of ETEC infecting pigs?

Answer 18

The adhesion factors found in ETEC infecting pigs are F4 (F4a,b; F4a,c; F4a,d), F5, F6, F18, and F41.

Question 19

What is the most important adhesion factor found in serotypes of ETEC infecting pigs?

Answer 19

F4 is the most important adhesion factor found in serotypes of ETEC infecting pigs because it occurs most often and it affects neonatal pigs all the way up to post-weaning age pigs. This means that if watery diarrhea is occurring in an older pig it has to be a F4 serotype.

Question 20

What two ETEC adhesion factors are located on the plasmid? Why is this important?

Answer 20

ETEC adhesion factors F4 and F5 are located on the plasmid. This is important because co-infection of other E. coli strains can lead to transmission of plasmid virulence factors.

Question 21

True or False:

One way to prevent ETEC infection is to breed for pigs lacking the F4 receptor.

Answer 21

True. If piglets do not have the F4 receptor, the F4 ETEC cannot adhere.

Question 22

What age group of piglets will develop watery diarrhea from an infection of a F5 serotype of ETEC?

Answer 22

The receptor for the F5 serotype of ETEC is only present in the piglet for its first 5 days of life, so this serotype of ETEC can only cause disease in neonates less than 5 days-old.

Question 23

Where do ETEC adhere in pigs?

Answer 23

ETEC adheres to adhesion receptors in the small intestine of the pig host.

Question 24

What non-fimbrial adhesin factor(s) of ETEC is/are currently used in vaccines?

Answer 24

AIDA-I (adhesin involved in diffuse adherence) is the only non-fimbrial adhesin included in vaccines for pig ETEC.

Question 25

Which adhesion factor of ETEC will not be able to infect a piglet less than 10 days-old?

Answer 25

F18 ETEC can only adhere to the small intestine of piglet from 10 days on.

Question 26

What ETEC enterotoxins are located on the plasmid? Why is this important?

Answer 26

All ETEC enterotoxins (LT, STa, STb, and EAST1) are located on the plasmid. This is important because co-infection of other E. coli strains can lead to transmission of plasmid virulence factors.

Question 27

True or False: | Generally, the higher the molecular weight the more antigenic a molecule is.

Answer 27

True.

Question 28

Which enterotoxin(s) of ETEC is/are used in vaccines?

Answer 28

The heat labile (LT) enterotoxin of pig ETEC has a high molecular weight, making it a strong antigen, causing an increased antibody response, which is why it is used in vaccines.

Question 29

How does LT enterotoxin of ETEC influence the adenylate cyclase system? Why is this important?

Answer 29

LT enterotoxin of ETEC activates the adenylate cyclase system, increasing cAMP, decreasing sodium (Na+) absorption, increasing chloride (Cl-) secretion, and increasing bicarbonate (HCO3+) secretion. This electrolyte imbalance produces the watery diarrhea seen in ETEC infections.

Question 30

Which is of ETEC's enterotoxins are more pathogenic, heat labile or heat stable? Why?

Answer 30

LT enterotoxin of ETEC activates the adenylate cyclase system, whereas the heat stable enterotoxin STa activates the guanylate cyclase system. Activation of the guanylate cyclase system causes a more severe electrolyte imbalance, resulting in a more severe watery diarrhea. Therefore STa (heat stable) is more pathogenic than LT.

Question 31

What factor(s) is/are targeted when vaccinating for heat stable ETEC?

Answer 31

Fimbriae (F) antigens are targeted when vaccinating for heat stable enterotoxin serotypes of ETEC. This is because the heat stable enterotoxins of ETEC have a low molecular weight and therefore are not very antigenic.

Question 32

ETEC infections that only cause disease in neonatal pigs typically possess what virulence factors?

Answer 32

ETEC infections that only cause disease in neonatal pigs typically possess: - F5, F6, and/or F41 fimbriae - STa and/or STb enterotoxins - Non-hemolytic

Question 33

ETEC infections that cause disease in neonatal pigs all the way to 4 weeks of age typically possess what virulence factors?

Answer 33

ETEC infections that cause disease in neonatal pigs all the way to 4 weeks of age typically possess: - F4 fimbriae - LT, STa, STb, and/or EAST1 enterotoxins - Hemolytic

Question 34

ETEC infections that cause disease in weanling pigs typically possess what virulence factors?

Answer 34

ETEC infections that cause disease in weanling pigs typically possess: - F4 and/or F18 fimbriae - LT, STa, STb, and/or EAST1 enterotoxins - Hemolytic

Question 35

You find that a number of piglets have an ETEC infection. Where did the bacteria originate from?

Answer 35

ETEC is normally found in the intestine of healthy sows, so if there is an ETEC infection on the farm it is in the sows.

Question 36

A farmer tells you that a young sow has given birth to a very large litter of piglets. Describe how the age of the sow and litter size can increase the risk of E. coli infection.

Answer 36

Younger sows typically do not provide/generate high quality colostrum, decreasing the maternal antibodies passed on to the neonates. An increase in the litter size can result in decreased colostrum available per piglet, which can result in an immunodeficient litter.