Citrobacter freundii

Citrobacter freundii

Citrobacter freundii

Citrobacter freundii is a Gram negative rod bacteria that belongs to the Enterobacteriaceae family. They are aerobic and facultative anaerobes. They can cause a number of infections including urinary tract infections and sepsis. According to Whalen et al, 2007, C. freundii represents 29% of all opportunistic infections.

They grow on Chromogenic agar as shown above as pink or purple colonies due to its strong beta-galactosidase activity (Ford, 2010). They are typically citrate positive and can be differentiated from Salmonellae in that they do not decarboxylate lysine (Brooks et al, 1998). They are oxidase negative and catalase positive when tested in the laboratory. They are also negative to indole test which can be used as a rapid test to differentiate it from Escherichia coli which is indole positive from chromogenic agar where they produce similar colour.

References

Brooks G F, Butel J S and Morse S A (1998). Jawetz, Melnick and Adelberg’s Medical Microbiology. Appleton and Lange, Stamford, Cunnecticut, USA

Ford M (2010). Fundamentals of Biomedical Science; Medical Microbiology. Oxford University Press, London.
Whalen J.G, Mully T.W and English J.C (2007). Spontaneous Citrobacter freundii Infection in an Immunocompetent Patient. Archives of Dermatology 143 (1): 124–125.