title: Bacillus anthracis spore suspensions: determination of stability and comparison of enumeration techniques.
abstract: OBJECTIVE
  To determine the stability and variability in concentration of spore suspensions of Bacillus anthracis (BA) spore suspensions by comparing different methods of enumeration and to detect changes, if any, under different storage conditions.
  
  
  RESULTS
  Plate and microscope counts were compared to measuring the genomic equivalents based on DNA content BA spore suspensions. We developed chemical methods to extract spore DNA and extra-spore (ES) DNA. DNA mass was determined by gel electrophoresis and QPCR assays were developed using the markers on the chromosome (rpoB) and the pXO1 plasmid (pag). The plate counts and microscope counts were very stable (for up to 900 days). The effect of freezing and the presence of additives in samples were tested for up to 300 days, and the results indicated that the additives tested and freezing did not decrease the viability or microscope counts.
  
  
  CONCLUSIONS
  Bacillus anthracis spore suspensions can be stored for long periods of time without significant loss of viability or clumping. The content of ES DNA was variable and changed with time.
  
  
  CONCLUSIONS
  The study shows that BA spore suspensions can be developed for reference materials providing a uniform basis for comparing detection equipment and results from different laboratories.
authors.affiliation: Chemical Sciences and Technology Laboratory, National Institute of Standards and Technology, Gaithersburg, MD, USA.
authors.forename: J L
authors.initials: JL
authors.lastname: Almeida
authors.forename: B
authors.initials: B
authors.lastname: Harper
authors.forename: K D
authors.initials: KD
authors.lastname: Cole
mesh_terms: D000881:Anthrax / Q000382:microbiology; D001408:Bacillus anthracis / Q000235:genetics / Q000502:physiology*; D001431:Bacteriological Techniques; D017931:DNA Primers / Q000235:genetics; D004269:DNA, Bacterial / Q000032:analysis; D050296:Microbial Viability; D016133:Polymerase Chain Reaction / Q000379:methods; D011309:Preservation, Biological; D013171:Spores, Bacterial
chemical_list: D017931:DNA Primers; D004269:DNA, Bacterial