Citrobacter

Microbial biochemistry

The species C. amalonaticus, C. koseri, and C. freundii can use citrate as a sole carbon source. Citrobacter species are differentiated by their ability to convert tryptophan to indole (C. koseri is the only citrobacter to be commonly indole-positive), ferment lactose (C. koseri is a lactose fermentor), and use malonate.

Citrobacter shows the ability to accumulate uranium by building phosphate complexes.

Environmental microbiology

These bacteria can be found almost everywhere in soil, water, wastewater, etc. They can also be found in the human intestine.

Citrobacter are found in the intestinal tract of humans and transmission usually occurs through human to human contact. They are considered opportunistic nosocomial pathogens, typically associated with urinary tract infections and infant meningitis and sepsis.

Antimicrobial resistance

Citrobacter freundii strains have inducible ampC genes encoding resistance to ampicillin and first-generation cephalosporins. In addition, isolates of Citrobacter may be resistant to many other antibiotics as a result of plasmid-encoded resistance genes.