Citrobacter koseri is a bacteria which generally causes meningitis or multiple brain abscesses in newborns. It is rarely encountered in adults other than those whose immunity has been compromised by preexisting illnesses. For diagnosis a spinal tap is done and then cerebrospinal fluid collected is cultured for bacteria.The bacteria is commonly present in the urinary & gastrointestinal tract. Infection in the newborns is due to transmission from the mother or nursing staff. Strict adherence to hygiene(frequent hand washing etc) is the only preventive measure Do write for more info.