Neonatal meningitis caused by Citrobacter koseri.

Three cases of neonatal meningitis, two of which were fatal, occurred in a premature baby unit during a period of one week. A fourth case occurred in the same unit six months later. Citrobacter koseri was isolated from the cerebrospinal fluid of all four cases. Detailed biochemical and serological examination of the organisms showed that two distinct bioserotypes were involved.