Citrobacter

Citrobacter is a genus of Gram-negative, rod-shaped coliform bacteria in the Enterobacteriaceae family, at home in the intestines of humans and other vertebrates as well as in water, sewage, and soil. Its members turn up in dairy products, raw shellfish, raw poultry, and fresh vegetables, and two species — C. freundii and C. diversus — can cause diarrhoea in people. For food microbiologists the genus is a hygiene flag: finding it suggests faecal or environmental contamination and sends investigators checking water quality, sanitation, and handling practices before a bigger problem develops.