Epidemiologic marker system for Citrobacter diversus using outer membrane protein profiles.

Investigations of nursery outbreaks of Citrobacter diversus sepsis and meningitis have been hampered by lack of adequate epidemiologic markers for the organism. We studied outer membrane protein profiles from clinical isolates of C. diversus by sodium dodecyl sulfate-polyacrylamide gel electrophoresis to determine whether this method might be useful in the epidemiologic differentiation of strains. Paired cerebrospinal fluid isolates from each of three separate nursery outbreaks of C. diversus meningitis, paired isolates from the vagina of a postpartum woman and the cerebrospinal fluid of her newborn infant, one isolate from an infant with pneumonia and two from colonized nursery cohorts, and 30 epidemiologically unrelated clinical isolates were included. Eleven distinct profiles were differentiated by the presence or absence of five outer membrane proteins. Complete concordance of profiles was observed for epidemiologically related isolates. Unrelated epidemic strains had outer membrane protein profiles distinct from one another. Biotyping complemented determination of outer membrane protein profiles; the two markers differentiated each of the five epidemic strains from all but one of 30 unrelated nonepidemic isolates. Determination of outer membrane protein profiles is potentially useful in epidemiologic investigations of disease caused by C. diversus.