title: The relationship between ecophysiology, indigenous microflora and growth of Listeria monocytogenes in grass silage.
abstract: The combined effect of the physical and chemical parameters (oxygen tension, pH and dry matter) influencing Listeria monocytogenes growth and survival in silage were simultaneously studied in a model in vitro system. Ensiled grass was exposed to a range of low oxygen concentrations, 0-5% v/v, and their effect was recorded with respect to acidification and microbial population dynamics of the epiphytic microflora, i.e. lactic acid bacteria, enterobacteria, yeasts, moulds and L. monocytogenes in grasses pre-inoculated with the latter. Listeria monocytogenes survival depended on the establishment of a fine balance between the physico-chemical and microbiological characteristics, i.e. oxygen tension, dry matter, pH, grass and microbiological quality. In all grasses ensiled, an oxygen concentration of 1.0% or greater sustained L. monocytogenes growth, below this level growth was shown to be principally dependent on the rate and quality of the fermentation. In most grasses 0.5% oxygen prolonged survival, whereas 0.1% and 0% oxygen caused L. monocytogenes to die off. In very poor quality grass with a restricted fermentation L. monocytogenes survival was prolonged even under anaerobic conditions.
authors.affiliation: Department of Agriculture, University of Aberdeen, UK.
authors.forename: A S
authors.initials: AS
authors.lastname: Donald
authors.forename: D R
authors.initials: DR
authors.lastname: Fenlon
authors.forename: B
authors.initials: B
authors.lastname: Seddon
mesh_terms: D000693:Anaerobiosis; D017753:Ecosystem; D004783:Environmental Microbiology; D005285:Fermentation; D005658:Fungi / Q000254:growth & development; D006863:Hydrogen-Ion Concentration; D008089:Listeria monocytogenes / Q000254:growth & development*; D008954:Models, Biological; D010100:Oxygen / Q000494:pharmacology; D006109:Poaceae / Q000254:growth & development / Q000378:metabolism / Q000382:microbiology*; D012820:Silage / Q000382:microbiology*; D013997:Time Factors
chemical_list: D010100:Oxygen