title: Proton Transfer Reaction Mass Spectrometry detects rapid changes in volatile metabolite emission by Mycobacterium smegmatis after the addition of specific antimicrobial agents.
abstract: The metabolic activity of plants, animals or microbes can be monitored by gas headspace analysis. This can be achieved using Proton Transfer Reaction Mass Spectrometry (PTR-MS), a highly sensitive detection method for trace gas analysis. PTR-MS is rapid and can detect metabolic responses on-line as they occur. Here, we study the headspace of actively growing cultures of paired ciprofloxacin sensitive and resistant bacterial strains (Mycobacterium smegmatis in Middlebrook M7H9 liquid media) after the addition of the antibiotics ciprofloxacin and gentamicin in real time. Following the emission patterns of the mycobacteria over time allowed volatile markers specific for the bacterial response to each antibiotic to be detected. A proportion of the measured responses were very rapid, occurring within three hours after the addition of the compounds and varied between isolates with different resistance phenotypes. Specifically, we observed a two fold increase of m73 (unidentified C4 compound) within 10h after the addition of ciprofloxacin and a threefold increase of m45 (acetaldehyde) within 4h after the addition of gentamicin as compared to values before the addition. Monitoring the emission of specific volatiles into the culture headspace thus has the potential for rapid drug susceptibility testing. Moreover, these and other differences in the measured responses to the two tested compounds provide evidence that monitoring multiple compounds may also give an indication of the mechanism of action of the compound added.
authors.affiliation: Life Science Trace Gas Facility, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands.
authors.forename: E
authors.initials: E
authors.lastname: Crespo
authors.forename: S M
authors.initials: SM
authors.lastname: Cristescu
authors.forename: H
authors.initials: H
authors.lastname: de Ronde
authors.forename: S
authors.initials: S
authors.lastname: Kuijper
authors.forename: A H J
authors.initials: AH
authors.lastname: Kolk
authors.forename: R M
authors.initials: RM
authors.lastname: Anthony
authors.forename: F J M
authors.initials: FJ
authors.lastname: Harren
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D013058:Mass Spectrometry / Q000295:instrumentation / Q000379:methods*; D020102:Mycobacterium smegmatis / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D055549:Volatile Organic Compounds / Q000032:analysis / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D055549:Volatile Organic Compounds