E. coli Flashcards
True or False:
Of the genus Escherichia, there are a number of species known to be clinically relevant.
False. Of the genus Escherichia, there are a number of species, but Escherichia coli is the only clinically relevant species known.
Define serotype.
Serotype: complete antigenic formula of an organism
What are the four antigenic variables used in serotyping and what do they describe?
The four antigenic variables used in serotyping are: O - O antigen H - Flagella F - Fimbriae K - Capsule
Which of the four antigenic variables is involved in bacterial adhesion?
Fimbriae (F) are involved in adhesion. Non-fimbrial adhesins also play a role in adhesion, but they are used in serotyping.
True or False:
All E. coli present in an animal are pathogenic.
False. E. coli are a very diverse species with many different serotypes, most of which are commensal.
True or False:
Domestic animals do not develop shigellosis.
True. Shigella spp. are only present in humans, so domestic animals do not develop shigellosis.
What does it mean if a strain of E. coli is an obligate pathogen?
The pathogenicity of E. coli is strain-dependent. If the strain is an obligate pathogen then it is also age-dependent.
How do we identify pathogenic types of avian E. coli?
Avian pathogenic E. coli (APEC) are identified by their O antigens, where O: 1, 2, 78 indicate pathogenic strains.
What type(s) of pathogenic E. coli utilize serotyping and biotyping for identification?
Rabbit pathogenic E. coli (RPEC) are identified using serotyping and biotyping.
What is bacterial lipopolysaccharide associated with on the cell?
Lipopolysaccharide (LPS) is associated with the bacterial cell wall.
What are the two categories of virulence factors?
Virulence factors are categorized as either cell-associated or extracellular.
True or False:
Extracellular virulence factors of E. coli are secreted from the bacteria.
True.
What are siderophores?
Siderophores are iron-sequestering molecules that deliver iron to the bacteria to enhance growth.
What are the five enteric pathotypes of E. coli that occur in domestic species?
The five enteric pathotypes of E. coli that occur in domestic species include:
- Enterotoxigenic (ETEC)
- Enterohemorrhagic (EHEC)
- Verotoxigenic (VTEC)/Shiga-like toxic (STEC)
- Enteropathogenic (EPEC)
- Rabbit pathogenic (RPEC)
True or False:
E. coli does not cause diarrhea in adult pigs.
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.
ETEC causes diarrhea in piglets of what age groups?
Enterotoxigenic E. coli (ETEC) causes watery diarrhea in neonates, piglets between 2 and 4 weeks of age, and weanlings.
What factors cause disease in a piglet with an ETEC infection? Why are they important?
The adhesion factors and the enterotoxins are the factors causing disease. They are important because you can vaccinate for them.
What are the adhesion factors found in serotypes of ETEC infecting pigs?
The adhesion factors found in ETEC infecting pigs are F4 (F4a,b; F4a,c; F4a,d), F5, F6, F18, and F41.
What is the most important adhesion factor found in serotypes of ETEC infecting pigs?
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.
What two ETEC adhesion factors are located on the plasmid? Why is this important?
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.
True or False:
One way to prevent ETEC infection is to breed for pigs lacking the F4 receptor.
True. If piglets do not have the F4 receptor, the F4 ETEC cannot adhere.
What age group of piglets will develop watery diarrhea from an infection of a F5 serotype of ETEC?
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.
Where do ETEC adhere in pigs?
ETEC adheres to adhesion receptors in the small intestine of the pig host.
What non-fimbrial adhesin factor(s) of ETEC is/are currently used in vaccines?
AIDA-I (adhesin involved in diffuse adherence) is the only non-fimbrial adhesin included in vaccines for pig ETEC.
Which adhesion factor of ETEC will not be able to infect a piglet less than 10 days-old?
F18 ETEC can only adhere to the small intestine of piglet from 10 days on.
What ETEC enterotoxins are located on the plasmid? Why is this important?
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.
True or False:
Generally, the higher the molecular weight the more antigenic a molecule is.
True.
Which enterotoxin(s) of ETEC is/are used in vaccines?
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.
How does LT enterotoxin of ETEC influence the adenylate cyclase system? Why is this important?
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.
Which is of ETEC’s enterotoxins are more pathogenic, heat labile or heat stable? Why?
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.
What factor(s) is/are targeted when vaccinating for heat stable ETEC?
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.
ETEC infections that only cause disease in neonatal pigs typically possess what virulence factors?
ETEC infections that only cause disease in neonatal pigs typically possess:
- F5, F6, and/or F41 fimbriae
- STa and/or STb enterotoxins
- Non-hemolytic
ETEC infections that cause disease in neonatal pigs all the way to 4 weeks of age typically possess what virulence factors?
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
ETEC infections that cause disease in weanling pigs typically possess what virulence factors?
ETEC infections that cause disease in weanling pigs typically possess:
- F4 and/or F18 fimbriae
- LT, STa, STb, and/or EAST1 enterotoxins
- Hemolytic
You find that a number of piglets have an ETEC infection. Where did the bacteria originate from?
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.
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.
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.
