title: Bacteria detection based on the evolution of enzyme-generated volatile organic compounds: determination of Listeria monocytogenes in milk samples.
abstract: The rapid detection of Listeria monocytogenes contamination in food is essential to prevent food-borne illness in humans. The aim of this study was to differentiate non-contaminated milk from milk contaminated with L. monocytogenes using enzyme substrates coupled with the analysis of volatile organic compounds (VOCs). The method is based on the activity of β-glucosidase and hippuricase enzymes and the detection of a specific VOC i.e. 2-nitrophenol and 3-fluoroaniline, respectively. VOCs were extracted, separated and detected by headspace-solid phase microextraction coupled to gas chromatography-mass spectrometry (HS-SPME GC-MS). This approach required the inclusion of the selective agent's cycloheximide, nalidixic acid and acriflavine HCl in the growth medium to inhibit interfering bacteria. The VOCs were liberated by L. monocytogenes provided that samples contained at least 1-1.5×10(2) CFU ml(-1) of milk prior to overnight incubation. This approach shows potential for future development as a rapid method for the detection of L. monocytogenes contaminated milk.
authors.affiliation: Department of Applied Sciences, Northumbria University, Ellison Building, Newcastle upon Tyne NE1 8ST, UK.
authors.forename: Emma
authors.initials: E
authors.lastname: Tait
authors.affiliation: Department of Microbiology, Freeman Hospital, Newcastle upon Tyne NE7 7DN, UK.
authors.forename: John D
authors.initials: JD
authors.lastname: Perry
authors.affiliation: Department of Applied Sciences, Northumbria University, Ellison Building, Newcastle upon Tyne NE1 8ST, UK.
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Stanforth
authors.affiliation: Department of Applied Sciences, Northumbria University, Ellison Building, Newcastle upon Tyne NE1 8ST, UK. Electronic address: John.Dean@northumbria.ac.uk.
authors.forename: John R
authors.initials: JR
authors.lastname: Dean
mesh_terms: D000581:Amidohydrolases / Q000378:metabolism*; D000814:Aniline Compounds / Q000032:analysis / Q000302:isolation & purification / Q000378:metabolism; D000818:Animals; D005464:Fluorobenzenes / Q000032:analysis / Q000302:isolation & purification / Q000378:metabolism; D005516:Food Microbiology / Q000379:methods*; D008401:Gas Chromatography-Mass Spectrometry; D008089:Listeria monocytogenes / Q000201:enzymology / Q000302:isolation & purification*; D008892:Milk / Q000382:microbiology*; D009596:Nitrophenols / Q000032:analysis / Q000302:isolation & purification / Q000378:metabolism; D052616:Solid Phase Extraction; D055549:Volatile Organic Compounds / Q000032:analysis* / Q000302:isolation & purification / Q000378:metabolism; D001617:beta-Glucosidase / Q000378:metabolism*
chemical_list: D000814:Aniline Compounds; D005464:Fluorobenzenes; D009596:Nitrophenols; D055549:Volatile Organic Compounds; C079598:3-fluoroaniline; C045573:2-nitrophenol; D001617:beta-Glucosidase; D000581:Amidohydrolases; C019672:aminoacylase I
keywords: Enzyme substrates; Food; Headspace solid-phase microextraction gas chromatography–mass spectrometry; Listeria monocytogenes; Volatile organic compounds