title: Reproducibility of Staphylococcus epidermidis plasmid profiles.
abstract: The plasmid profiles of six isolates of Staphylococcus epidermidis were repetitively evaluated over an 8-month period. Each isolate was subcultured and stored at three different temperatures (-70 degrees C, -20 degrees C, and room temperature) and plasmid DNA was prepared from each subculture at 0, 1, 4, and 8 months by two different methods of plasmid extraction [using mixed alkyltrimethylammonium bromide (ATAB) or Brij 58 and deoxycholate (modified Parisi)]. Plasmid DNA bands were lost from two isolates when subcultures were kept at room temperature. This plasmid loss was confirmed by repetitive extractions and electrophoresis, as well as by restriction endonuclease analysis of the ATAB preparations. Profiles were otherwise highly related to one another, with occasional exceptions being extra or missing plasmid DNA bands of high molecular size. The latter findings were not reproducible. Plasmid DNA extracted by the modified Parisi method was not reliably digested with restriction endonuclease enzymes. We conclude that the plasmid profiles of Staphylococcus epidermidis isolates are highly reproducible as long as isolates are stored at less than or equal to -20 degrees C. Minor discrepancies in the number of plasmid DNA bands of large molecular size may occur. These are resolvable by repetitive testing or restriction endonuclease analysis of ATAB-extracted plasmid DNA preparations.
authors.affiliation: Department of Hospital Infection Control, University Hospitals, Portland, Oregon.
authors.forename: A I
authors.initials: AI
authors.lastname: Hartstein
authors.forename: V H
authors.initials: VH
authors.lastname: Morthland
authors.forename: A L
authors.initials: AL
authors.lastname: Rashad
mesh_terms: D003080:Cold Temperature; D004269:DNA, Bacterial / Q000032:analysis*; D004587:Electrophoresis, Agar Gel; D006801:Humans; D010957:Plasmids; D011309:Preservation, Biological; D015203:Reproducibility of Results; D015183:Restriction Mapping; D013212:Staphylococcus epidermidis / Q000235:genetics*
chemical_list: D004269:DNA, Bacterial