The genus Citrobacter was originally distinguished from other members of the Enterobacteriaceae by its ability to use citrate as a carbon source. Citrobacter infection is commonly reported in neonates and immunocompromised patients. Citrobacter koseri, formerly known as Citrobacter diversus, is best known as the cause of sepsis and meningitis leading to central nervous system (CNS) abscesses in neonates and young infants. The majority of cases are sporadic, with no clear source of infection. A significant number of the infants with abscesses die, and many sustain CNS damage. It adults, however, Citrobacter infection with central nervous system involvement is rare, and is usually associated with an underlying disorder. Citrobacter koseri (strain ATCC BAA-895 / CDC 4225-83 / SGSC4696) was isolated in 1983 in Maryland where it caused neonatal meningitis.