title: Identification of bacteria by fatty acid profiling with direct analysis in real time mass spectrometry.
abstract: BACKGROUND
  Bacterial fatty acid profiling is a well-established technique for bacterial identification. Current methods involving esterification and gas chromatography/mass spectrometry (GC/MS) or matrix-assisted laser desorption/ionization (MALDI) analysis are effective, but there are potential benefits to be gained by investigating ambient ionization methods that can provide rapid analysis without derivatization or additional sample handling.
  
  
  METHODS
  Lipid extracts from colonies of five Gram-positive and five Gram-negative pathogenic bacteria were analyzed by Direct Analysis in Real Time (DART) ionization coupled with a time-of-flight mass spectrometer. Fatty acid profiles were obtained from the negative-ion DART mass spectra without additional derivatization or sample preparation.
  
  
  RESULTS
  Fatty acid profiles obtained from the deprotonated molecules [M - H](-) were found to be highly species-specific and reproducible. Leave-one-out cross validation (LOOCV) for principal component analysis (PCA) showed 100% correct classification accuracy.
  
  
  CONCLUSIONS
  The results of this preliminary feasibility study show good precision and accuracy, and the fatty acid patterns are clearly distinctive for each of the ten species examined. The speed and ease of analysis and the high classification accuracy for this initial study indicate that DART is an effective method for bacterial fatty acid profiling.
authors.affiliation: JEOL USA, Inc., 11 Dearborn Rd., Peabody, MA, 01960, USA.
authors.forename: Robert B
authors.initials: RB
authors.lastname: Cody
authors.affiliation: Colorado School of Mines, 1012 14th Street, Golden, CO, 80401, USA.
authors.forename: Casey R
authors.initials: CR
authors.lastname: McAlpin
authors.affiliation: Colorado School of Mines, 1012 14th Street, Golden, CO, 80401, USA.
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Cox
authors.affiliation: Colorado School of Mines, 1012 14th Street, Golden, CO, 80401, USA.
authors.forename: Kirk R
authors.initials: KR
authors.lastname: Jensen
authors.affiliation: Colorado School of Mines, 1012 14th Street, Golden, CO, 80401, USA.
authors.forename: Kent J
authors.initials: KJ
authors.lastname: Voorhees
mesh_terms: D001419:Bacteria; D005227:Fatty Acids / Q000737:chemistry* / Q000378:metabolism; D006090:Gram-Negative Bacteria / Q000737:chemistry* / Q000378:metabolism; D013058:Mass Spectrometry / Q000379:methods*
chemical_list: D005227:Fatty Acids