Enterobacteriaceae

Overview

The Enterobacteriaceae is a large family of Gram-negative bacteria that includes many of the more familiar pathogens, such as Escherichia coli, Salmonella, and Klebsiella. Members of this family are commonly found in the intestines of humans and other animals, as well as in the environment.

Characteristics

Enterobacteriaceae are typically rod-shaped, and they are facultative anaerobes, meaning they can grow in both the presence and absence of oxygen. They are characterized by their ability to ferment glucose and other carbohydrates, often producing gas as a byproduct. Most members of this family are motile, possessing flagella, although some, like Klebsiella, are non-motile.

Pathogenicity

Many Enterobacteriaceae are pathogenic, causing a range of diseases in humans and animals. For example, Escherichia coli can cause urinary tract infections, gastroenteritis, and neonatal meningitis. Salmonella species are well-known for causing food poisoning and typhoid fever.

Citrobacter freundii

Citrobacter freundii colonies on agar

Citrobacter freundii is a species within the Enterobacteriaceae family. It is a Gram-negative, facultatively anaerobic, rod-shaped bacterium. C. freundii is commonly found in the environment, including soil, water, and sewage, and is also part of the normal gut flora in humans and animals.

Clinical Significance

Citrobacter freundii is an opportunistic pathogen, meaning it typically does not cause disease in healthy individuals but can cause infections in those with weakened immune systems. It is associated with urinary tract infections, respiratory tract infections, and bacteremia.

Antibiotic Resistance

C. freundii is known for its ability to acquire antibiotic resistance genes, making infections difficult to treat. It is often resistant to multiple antibiotics, including beta-lactams, due to the production of beta-lactamase enzymes.

Laboratory Identification

In the laboratory, Enterobacteriaceae can be identified using a variety of biochemical tests. Citrobacter freundii can be distinguished by its ability to ferment lactose slowly, produce hydrogen sulfide, and its positive citrate test.

Related pages

• Escherichia coli
• Salmonella
• Klebsiella
• Antibiotic resistance