Citrobacter is a genus of Gram-negative, aerobic, rod-shaped[2] coliform bacteria of the Enterobacteriaceae family.

[2] The species C. amalonaticus, C. koseri, and C. freundii can use citrate as a sole carbon source.

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

[5][6] Citrobacter are considered opportunistic nosocomial pathogens, typically associated with urinary tract infections and infant meningitis and sepsis.

[7] Citrobacter freundii strains have inducible ampC genes encoding resistance to ampicillin and first-generation cephalosporins.