Bacteria commonly found in the environment - soil, water, sewages - and is responsible for reducing nitrate to nitrite. As an opportunistic pathogen, C. freundii is also responsible for a number of significant infections of the respiratory tract, urinary tract, blood and several other normally sterile sites. It might be also causing systemic body odor in humans. C. freundii represents approximately 29% of all opportunistic infections. It is one of the most common hydrogen sulfide-producing species of bacteria along with Hafnia alvei, Pseudomonas, Citrobacter, Aeromonas, Salmonella, and Escherichia coli