Citrobacter diversus brain abscess: case reports and molecular epidemiology.

Citrobacter diversus brain abscess occurred in two infants in Aberdeen, 5 months apart. These are the first reported cases of this condition in the UK since 1976. Restriction endonuclease analysis with SacI enzyme showed blood and CSF isolates from both patients to be identical and different from 10 other clinical isolates of C. diversus and one C. amalonaticus strain. Furthermore, isolates of C. diversus from patients belonged to biotype "d" whereas control isolates were of biotypes "a" or "e". Because both infants attended the same central and peripheral maternity units, this raised suspicions of long term contamination of the hospital environment by this organism. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) patterns of whole-cell proteins and immunoblotting with normal human serum were remarkably homogeneous for all 13 C. diversus strains and thus were not useful for typing. However, the only C. amalonaticus strain was clearly differentiated from C. diversus strains by SDS-PAGE. Management of the infants included multiple intravenous antibiotic therapy for 4-6 weeks and repeated computerised tomography (CT) scanning and drainage of the abscess cavity. Both children survived albeit with some minor degree of brain damage.