title: Synergistic inhibition of Listeria monocytogenes in vitro through the combination of octanoic acid and acidic calcium sulfate.
abstract: It has been hypothesized that inhibition of foodborne pathogens can be enhanced by using antimicrobials in combination. A broth dilution assay was devised to determine whether inhibition of Listeria monocytogenes exposed to the combination of the fatty acid octanoic acid (OCT) and the organic acid-containing antimicrobial acidic calcium sulfate (ACS) was enhanced compared with the inhibition of the pathogen exposed to either antimicrobial applied singly. MICs for OCT and ACS were 25.00 μg/g and 1.56 ml/liter, respectively, for all strains of the pathogen tested. Fractional inhibitory concentrations (FICs) from the combination exposures were calculated for use in characterizing the antimicrobial interaction as antagonistic, additive indifferent, or synergistic with respect to L. monocytogenes inhibition. Combining OCT and ACS resulted in observed synergistic inhibition of L. monocytogenes; isobolograms for all strains curved toward the origin, and FIC indices (FIC(I)s) were <1.0. Future investigations of the antimicrobial combination should focus on determining the mechanism of action of combined antimicrobials and the levels of antimicrobials required for pathogen inhibition on the surfaces of ready-to-eat meats.
authors.affiliation: Center for Food Safety, Department of Animal Science, Texas AgriLife Research, College Station, Texas 77843-2471, USA.
authors.forename: Alex L
authors.initials: AL
authors.lastname: Brandt
authors.forename: Alejandro
authors.initials: A
authors.lastname: Castillo
authors.forename: Kerri B
authors.initials: KB
authors.lastname: Harris
authors.forename: Jimmy T
authors.initials: JT
authors.lastname: Keeton
authors.forename: Margaret D
authors.initials: MD
authors.lastname: Hardin
authors.forename: T Matthew
authors.initials: TM
authors.lastname: Taylor
mesh_terms: D002133:Calcium Sulfate / Q000494:pharmacology*; D002210:Caprylates / Q000494:pharmacology*; D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D005519:Food Preservation / Q000379:methods*; D006801:Humans; D008089:Listeria monocytogenes / Q000187:drug effects* / Q000254:growth & development; D008461:Meat Products / Q000382:microbiology; D008826:Microbial Sensitivity Tests; D013997:Time Factors
chemical_list: D002210:Caprylates; C031492:octanoic acid; D002133:Calcium Sulfate