24 Questions
What is the shape of Enterobacterales bacteria?
Strait, cylindrical, with rounded ends
What is the significance of the term 'coliforms' in Enterobacteriaceae?
Enterobacteriaceae that ferment lactose
What is the primary mode of respiration for Enterobacterales?
Facultative anaerobes
What is the characteristic of Enterobacterales regarding nitrate?
Nitrate -> nitrite
What is the primary habitat of Enterobacteriaceae?
Plants, soil, and water
What is the approximate number of organisms per gram of feces for Escherichia coli?
10^8
What is the typical behavior of Enterobacteriaceae Escherichia coli in the environment?
It survives in the environment, but does not multiply
What is the primary host affected by Enterotoxigenic E. coli (ETEC) in terms of age and species?
Piglets, calves, and lambs
What is the primary function of fimbriae in Enterobacteriaceae Escherichia coli?
To attach to host cells
What is the range of E. coli genome size?
4.5-5.5 Mbp
What is the function of adhesins in Enterotoxigenic E. coli (ETEC)?
To facilitate bacterial adhesion to host cells
What is the function of siderophores in Enterobacteriaceae Escherichia coli?
To acquire iron from the host
What is the outcome of Enterotoxigenic E. coli (ETEC) infection in the intestinal lumen?
Accumulation of Cl-, HCO3-, and Na+ ions and water in the intestinal lumen
Which of the following is NOT a type of enterotoxin produced by Enterotoxigenic E. coli (ETEC)?
CT (heat-labile toxin)
How many O antigens are used in the international typing scheme for E. coli?
181 O-antigens
What is the name of the non-fimbrial adhesin produced by Enterotoxigenic E. coli (ETEC) that affects piglets?
AIDA-I
What is the primary location of E. coli concentration in the human body?
Large intestine
How many major intestinal pathogroups of Escherichia coli are recognized?
6
What is the primary cause of severe watery diarrhea in ETEC infections?
Secretion of enterotoxins by ETEC
What is the primary factor that contributes to the development of neonatal diarrhea in piglets?
Lowering of maternal immunity
What is the main reason for the change in the composition of the indigenous flora in piglets after weaning?
Change in diet
Which of the following is a characteristic of ETEC infections?
Non-inflammatory secretory diarrhea
What is the primary consequence of ETEC infections in young animals?
All of the above
What is the age range during which ETEC infections are most commonly observed in piglets?
Up to 6 weeks after birth
Study Notes
Enterobacteriaceae
- Enterobacteriaceae is a family of Gram-negative rods (coccobacilli) that are non-sporulating, facultative anaerobes, and motile (peritrichate flagella) or non-motile.
- They have simple nutritional requirements, and are able to ferment sugars, producing acid and gas.
- There are over 40 genera and 180 species in the Enterobacteriaceae family.
Escherichia coli
- Escherichia coli (E. coli) is a type species of the Enterobacteriaceae family and is present in the intestine of most animal species.
- E. coli is a commensal, surviving in the environment but usually not multiplying.
- The concentration of E. coli is higher in the large intestine.
Virulence Factors
- E. coli has several virulence factors, including:
- Capsule
- Endotoxin (lipid A)
- Fimbriae (some are adhesins)
- Flagella
- Siderophores
- Enterotoxins (Heat-stable and Heat-labile)
- Other toxins (Shiga-like toxin, hemolysins)
Serotyping
- E. coli serotyping is based on three main antigens:
- Capsule (K antigens)
- Somatic (O antigens)
- Flagellar (H antigens)
- There are 181 O-antigens and 53 H antigens in the international typing scheme.
Pathogenicity
- E. coli can cause diarrheagenic/intestinal (DEC or InPEC) and extraintestinal (ExPEC) infections.
- There are 6 major intestinal pathogroups:
- Enterotoxigenic E. coli (ETEC)
- Enteropathogenic E. coli (EPEC)
- Enterohemorrhagic E. coli (EHEC)
- Enteroaggregative E. coli (EAEC)
- Enteroinvasive E. coli (EIEC)
- Diffusely-adherent E. coli (DAEC)
Enterotoxigenic E. coli (ETEC)
- ETEC is an important pathogen of calves, piglets, and lambs.
- Host specificity is influenced by species and age.
- Key virulence factors include enterotoxins (STa, STb, LT, and EAST1) and adhesins (F4, F5, F6, F17, F18, F41, and AIDA-I).
Pathogenesis of ETEC
- ETEC causes accumulation of Cl-, HCO3-, and Na+ ions and water in the intestinal lumen, leading to severe watery diarrhea.
- Adherence is a critical step in the pathogenesis of ETEC, and is influenced by the presence or absence of fimbriae genes and the expression of fimbriae receptors in the intestinal lining.
Clinical Presentation of ETEC in Piglets
- ETEC causes neonatal diarrhea (colibacillosis) and post-weaning diarrhea (PWD) in piglets.
- Neonatal diarrhea is often associated with factors such as low maternal immunity, low birth weight, and poor hygiene.
- Post-weaning diarrhea is influenced by changes in the intestinal environment of piglets, particularly dietary changes, which alter the composition of the indigenous flora.
This quiz covers the general features and characteristics of Enterobacterales, a order of Gram-negative bacteria. Topics include their morphology, nutritional requirements, and metabolic processes.
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