Molecular epidemiology of neonatal meningitis due to Citrobacter diversus: a study of isolates from hospitals in Maryland.

Six cases of neonatal meningitis due to Citrobacter diversus were diagnosed in three Baltimore (Maryland) hospitals between 1983 and 1985. Using plasmid profiles, biotypes, serotypes, and chromosomal restriction endonuclease digests as epidemiological markers, we studied 63 isolates of C. diversus (including four isolates from cerebrospinal fluid) from these and seven other hospitals in Maryland. Within two of the three hospitals with meningitis cases, the same strain of C. diversus was isolated from case infant(s), healthy neonates, and nursery personnel. In all three hospitals, C. diversus strains different from those implicated as a cause of meningitis were also isolated. Other than the meningitis-associated strains, 15 different strains of C. diversus were isolated from infants in the hospitals studied, with several distinct clusters of asymptomatic, colonized infants identified.