Plasmid profiles in epidemiologic studies of infections by Staphylococcus epidermidis

Plasmid profiles of cultures of Staphylococcus epidermidis obtained by agarose gel electrophoresis were used, in conjunction with phage typing, biotyping, and antibiograms, in epidemiologic studies of infections in neonates and patients with cancer. In some cases, patients had cultures that were lysed by a single phage, belonged to the same biotype, and had identical antibiograms, but had distinctly different plasmid profiles. In other instances, almost identical plasmid profiles were observed in cultures lysed by a single phage, belonging to the same biotype, and with markedly different antibiograms. The plasmid profile technique was valuable in detecting distinct strains of S. epidermidis, and its use could be helpful in epidemiologic studies of infections by other organisms.