A unique plasmid profile characterizing Salmonella enteritidis isolates from patients and employees in a hospital

Plasmid profiling was used as an epidemiological tool during a period of frequent Salmonella enteritidis infection in a hospital. S. enteritidis was isolated from 22 patients and employees. Isolates from 18 persons harbored one 29 and one 36 megadalton (MDa) plasmid. The 29 MDa plasmid has not been previously described in this species and was not found in 54 control strains of S. enteritidis from other sources. The respective restriction endonuclease digest fragments of the 36 and the 29 MDa plasmids were always identical. This plasmid pattern thus served as a marker for the isolates from the outbreak.