title: Detection of mycobacteria by volatile organic compound analysis of invitro cultures using differential ion mobility spectrometry.
abstract: OBJECTIVE
  Differential ion mobility spectrometry (DMS) is an analytical technique used to detect volatile organic compounds (VOCs) in gaseous samples at very low concentration ranges from ppb to ppt. The aim of this study was to investigate whether VOC analysis by DMS is capable of detecting Mycobacterium avium subsp. paratuberculosis (MAP).
  
  
  METHODS
  Headspaces of in vitro cultures of two different MAP strains at 1, 2, 3, 4 and 6 weeks after inoculation (each at two dilutions) were analysed with DMS in comparison to control samples without viable bacteria [(i) blank medium, (ii) medium inoculated with heat-inactivated MAP and (iii) sterile-filtered MAP culture broth]. Furthermore, VOC patterns in the headspace over cultures of six non-tuberculous mycobacterial species were compared to MAP-derived VOC patterns. Data analysis included peak detection, cluster analysis, identification of discriminating VOC features (Mann-Whitney U test) and different cross-validated discriminant analyses.
  
  
  RESULTS
  VOC analysis resulted in up to 127 clusters and revealed highly significant differences between MAP strains and controls at all time points. In addition, few clusters allowed differentiation between MAP and other non-tuberculous mycobacteria and even between different MAP strains. Compounds have not been characterized. VOC analysis by DMS was able to identify MAP-positive samples after 1 week of in vitro growth.
  
  
  CONCLUSIONS
  This study provides strong evidence that VOC analysis of headspace over mycobacterial cultures in combination with appropriate data analysis has the potential to become a valuable method to identify positive samples much earlier than with current standard procedures.
authors.affiliation: IfU Diagnostic Systems GmbH, Gottfried-Schenker-Straße 18, 09244 Lichtenau, Germany.
authors.forename: Roman
authors.initials: R
authors.lastname: Purkhart
authors.affiliation: BecherConsult GmbH, Froebelweg 33, 16321 Bernau, Germany.
authors.forename: Gunther
authors.initials: G
authors.lastname: Becher
authors.affiliation: Institute of Molecular Pathogenesis, Friedrich-Loeffler-Institut (Federal Research Institute for Animal Health), Naumburger Str. 96a, 07743 Jena, Germany.
authors.forename: Petra
authors.initials: P
authors.lastname: Reinhold
authors.affiliation: Institute of Molecular Pathogenesis, Friedrich-Loeffler-Institut (Federal Research Institute for Animal Health), Naumburger Str. 96a, 07743 Jena, Germany.
authors.forename: Heike U
authors.initials: HU
authors.lastname: Köhler
mesh_terms: D000818:Animals; D003470:Culture Media / Q000737:chemistry; D005243:Feces / Q000382:microbiology; D016927:Mycobacterium avium subsp. paratuberculosis / Q000737:chemistry* / Q000254:growth & development / Q000302:isolation & purification* / Q000378:metabolism; D010283:Paratuberculosis / Q000175:diagnosis; D025341:Principal Component Analysis; D053719:Tandem Mass Spectrometry / Q000379:methods; D055549:Volatile Organic Compounds / Q000032:analysis* / Q000302:isolation & purification* / Q000378:metabolism
chemical_list: D003470:Culture Media; D055549:Volatile Organic Compounds