Citrobacter is a genus of Gram-negative bacteria in the family Enterobacteriaceae. There are several species within this genus, including Citrobacter freundii, Citrobacter koseri, Citrobacter braakii, and Citrobacter amalonaticus.

Citrobacter species are found in soil, water, and in the intestinal tracts of animals and humans. Some species can cause infections in humans, particularly in people with weakened immune systems or who are hospitalized. Common infections caused by Citrobacter include urinary tract infections, bloodstream infections, and pneumonia.

Citrobacter can be identified using laboratory tests, and treatment usually involves antibiotics that are effective against the specific species causing the infection. It is important to follow proper hygiene and infection control practices to prevent the spread of Citrobacter and other bacteria.