title: Effects of long-term storage on plasmid stability in Bacillus anthracis.
abstract: The plasmid profiles of 619 cultures of Bacillus anthracis which had been isolated and stored between 1954 and 1989 were analyzed using the Laboratory Response Network real-time PCR assay targeting a chromosomal marker and both virulence plasmids (pXO1 and pXO2). The cultures were stored at ambient temperature on tryptic soy agar slants overlaid with mineral oil. When data were stratified by decade, there was a decreasing linear trend in the proportion of strains containing both plasmids with increased storage time (P < 0.001). There was no significant difference in the proportion of strains containing only pXO1 or strains containing only pXO2 (P = 0.25), but there was a statistical interdependence between the two plasmids (P = 0.004). Loss of viability of B. anthracis cultures stored on agar slants is also discussed.
authors.affiliation: Centers for Disease Control and Prevention, 1600 Clifton Rd., MS G34, Atlanta, GA 30333, USA. cdk5@cdc.gov
authors.forename: Chung K
authors.initials: CK
authors.lastname: Marston
authors.forename: Alex R
authors.initials: AR
authors.lastname: Hoffmaster
authors.forename: Kathy E
authors.initials: KE
authors.lastname: Wilson
authors.forename: Sandra L
authors.initials: SL
authors.lastname: Bragg
authors.forename: Brian
authors.initials: B
authors.lastname: Plikaytis
authors.forename: Philip
authors.initials: P
authors.lastname: Brachman
authors.forename: Scott
authors.initials: S
authors.lastname: Johnson
authors.forename: Arnold F
authors.initials: AF
authors.lastname: Kaufmann
authors.forename: Tanja
authors.initials: T
authors.lastname: Popovic
mesh_terms: D001408:Bacillus anthracis / Q000235:genetics*; D001431:Bacteriological Techniques / Q000379:methods*; D010957:Plasmids; D016133:Polymerase Chain Reaction / Q000379:methods; D014774:Virulence / Q000235:genetics