Osteomyelitis Caused by Citrobacter koseri in a Young Immunocompetent Man.

Citrobacter koseri is a non-sporulating, motile, gram-negative, facultative anaerobic bacteria found in various environmental sources, including the human intestine. It is considered an opportunistic infection as it typically causes infection in newborns, elderly, and immunocompromised patients. Common sites of infection are the urinary tract, gastrointestinal system, and respiratory tract in immunocompromised adults, as well as the bloodstream and meninges in newborns. However, osteomyelitis secondary to C. koseri is very rare. We present an unusual case of Citrobacter osteomyelitis in a healthy young man with no identifiable risk factors.