Abstract
Agarose gel electrophoresis of the plasmid deoxyribonucleic acids from 60 gram-negative bacilli recovered during investigations of nosocomial epidemics was used to fingerprint the strains. This method was as specific at differentiating bacterial strains as more conventional phenotyping methods. In all cases, plasmid band fingerprints of epidermic strains isolates were identical whereas coisolate plasmid deoxyribonucleic acid patterns were different. Agarose gel electrophoresis of plasmid deoxyribonucleic acid is proposed as a method which can be used in conventional microbiology laboratories as an adjunct to or, possibly, replacement for other methods of identifying bacterial strains.