Identification of infant food as a vehicle in a nosocomial outbreak of Citrobacter freundii: epidemiological subtyping by allozyme, whole-cell protein and antibiotic resistance.

A total of 38 Citrobacter freundii strains was isolated from patients and their environment at a neonatal intensive care unit of a large hospital where colonization and clinical diseases due to the agent had been observed. Epidemiological investigations were carried out by subtyping, for which a combination of allozyme, whole-cell protein and resistance pattern analysis was used. Infant formula was identified as a vehicle of nosocomial spread. This shows that the role of foods in the transmission of hospital infections should not be underestimated. The combination of methods applied, in particular a limited enzyme set, is recommended also for epidemiological investigations of food-borne infections and establishment of their causes.