Enterobacterales: General Features and Characteristics

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Questions and Answers

What is the shape of Enterobacterales bacteria?

Fusiform

Cocci

Spiral

Strait, cylindrical, with rounded ends (correct)

What is the significance of the term 'coliforms' in Enterobacteriaceae?

A type of medium used to culture Enterobacteriaceae

A family of Enterobacteriaceae

Enterobacteriaceae that ferment lactose (correct)

A specific genus of Enterobacteriaceae

What is the primary mode of respiration for Enterobacterales?

Facultative anaerobes (correct)

Microaerophiles

Obligate anaerobes

Obligate aerobes

What is the characteristic of Enterobacterales regarding nitrate?

Nitrate -> nitrite Signup and view all the answers

What is the primary habitat of Enterobacteriaceae?

Plants, soil, and water Signup and view all the answers

What is the approximate number of organisms per gram of feces for Escherichia coli?

10^8 Signup and view all the answers

What is the typical behavior of Enterobacteriaceae Escherichia coli in the environment?

It survives in the environment, but does not multiply Signup and view all the answers

What is the primary host affected by Enterotoxigenic E. coli (ETEC) in terms of age and species?

Piglets, calves, and lambs Signup and view all the answers

What is the primary function of fimbriae in Enterobacteriaceae Escherichia coli?

To attach to host cells Signup and view all the answers

What is the range of E. coli genome size?

4.5-5.5 Mbp Signup and view all the answers

What is the function of adhesins in Enterotoxigenic E. coli (ETEC)?

To facilitate bacterial adhesion to host cells Signup and view all the answers

What is the function of siderophores in Enterobacteriaceae Escherichia coli?

To acquire iron from the host Signup and view all the answers

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 Signup and view all the answers

Which of the following is NOT a type of enterotoxin produced by Enterotoxigenic E. coli (ETEC)?

CT (heat-labile toxin) Signup and view all the answers

How many O antigens are used in the international typing scheme for E. coli?

181 O-antigens Signup and view all the answers

What is the name of the non-fimbrial adhesin produced by Enterotoxigenic E. coli (ETEC) that affects piglets?

AIDA-I Signup and view all the answers

What is the primary location of E. coli concentration in the human body?

Large intestine Signup and view all the answers

How many major intestinal pathogroups of Escherichia coli are recognized?

6 Signup and view all the answers

What is the primary cause of severe watery diarrhea in ETEC infections?

Secretion of enterotoxins by ETEC Signup and view all the answers

What is the primary factor that contributes to the development of neonatal diarrhea in piglets?

Lowering of maternal immunity Signup and view all the answers

What is the main reason for the change in the composition of the indigenous flora in piglets after weaning?

Change in diet Signup and view all the answers

Which of the following is a characteristic of ETEC infections?

Non-inflammatory secretory diarrhea Signup and view all the answers

What is the primary consequence of ETEC infections in young animals?

All of the above Signup and view all the answers

What is the age range during which ETEC infections are most commonly observed in piglets?

Up to 6 weeks after birth Signup and view all the answers

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.

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Description

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.