Inhibition of <i>Listeria monocytogenes</i> by Food Antimicrobials Applied Singly and in Combination

Brandt, Alex; Castillo, Alejandro; Harris, Kerri B.; Keeton, J.T.; Hardin, Margaret D.; Taylor, T. Matthew

doi:10.1111/j.1750-3841.2010.01843.x

Cited by 97 publications

(62 citation statements)

References 39 publications

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“…The MIC was 74 mg/liter for E. coli and 750 mg/liter for L. innocua. The MIC for E. coli was similar to previous reports (3,8,10), while we found somewhat higher MICs for L. innocua compared to previous studies that used the taxonomically similar L. monocytogenes (4,34).…”

Section: Resultssupporting

confidence: 44%

“…Bacterial suspensions were mixed with ε-PL dissolved in TSB to a final cell density of 5 ϫ 10 5 CFU/ml and a final ε-PL concentration of 0, 1/2ϫ MIC, MIC, or 2ϫ MIC. The CFU was determined after 0, 2,4,8,12,16,20, and 24 h of incubation at 25°C: 100 l cell the suspension was serial diluted to 10 Ϫ6 in Ringer's solution, and 20 l from each serial dilution step was transferred to two TSA plates, followed by incubation at 25°C for 24 h before the CFU were counted.…”

Section: Methodsmentioning

confidence: 99%

“…The safety of traditional preservatives has been questioned in the last few years, so to meet the consumers demand and at the same time ensure food safety, the food industry is turning to natural antimicrobials as preservatives. ε-Poly-Llysine (ε-PL) is a promising natural antimicrobial that has a broad spectrum of activity against food spoilage and food-poisoning bacteria in vitro (3)(4)(5) and in complex food matrices (6,7).…”

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confidence: 99%

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The Antimicrobial Mechanism of Action of Epsilon-Poly- l -Lysine

Hyldgaard

Mygind

Vad

et al. 2014

Appl Environ Microbiol

243

176

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Epsilon-poly-L-lysine (-PL) is a natural antimicrobial cationic peptide which is generally regarded as safe (GRAS) as a food preservative. Although its antimicrobial activity is well documented, its mechanism of action is only vaguely described. The aim of this study was to clarify -PL's mechanism of action using Escherichia coli and Listeria innocua as model organisms. We examined -PL's effect on cell morphology and membrane integrity and used an array of E. coli deletion mutants to study how specific outer membrane components affected the action of -PL. We furthermore studied its interaction with lipid bilayers using membrane models. In vitro cell studies indicated that divalent cations and the heptose I and II phosphate groups in the lipopolysaccharide layer of E. coli are critical for -PL's binding efficiency. -PL removed the lipopolysaccharide layer and affected cell morphology of E. coli, while L. innocua underwent minor morphological changes. Propidium iodide staining showed that -PL permeabilized the cytoplasmic membrane in both species, indicating the membrane as the site of attack. We compared the interaction with neutral or negatively charged membrane systems and showed that the interaction with -PL relied on negative charges on the membrane. Suspended membrane vesicles were disrupted by -PL, and a detergent-like disruption of E. coli membrane was confirmed by atomic force microscopy imaging of supported lipid bilayers. We hypothesize that -PL destabilizes membranes in a carpet-like mechanism by interacting with negatively charged phospholipid head groups, which displace divalent cations and enforce a negative curvature folding on membranes that leads to formation of vesicles/micelles.

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Section: Resultssupporting

confidence: 44%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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The Antimicrobial Mechanism of Action of Epsilon-Poly- l -Lysine

Hyldgaard

Mygind

Vad

et al. 2014

Appl Environ Microbiol

243

176

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“…This study shows a critical role of the L. monocytogenes two-component system response regulator VirR in resistance against antimicrobials intended for food preservation. Improved understanding of resistance mechanisms may facilitate the development of effective hurdle strategies utilizing different molecular targets (33). Additionally, the potential for cross-protection induced by a food-relevant stress (e.g., organic acids) should be taken into consideration to avoid unintended overestimation of preservative strength in a food system (20,42).…”

Section: Figmentioning

confidence: 99%

“…The microplate was stored at 7°C for 7 days, and the OD 600 was measured again. The MICs were defined as the lowest concentration that completely inhibited growth (OD 600 increase of Յ0.05) after 7 days of incubation at 7°C (32,33). MIC determinations were based on results with 3 biological replicates for all strains.…”

Section: Mic Determinationsmentioning

confidence: 99%

VirR-Mediated Resistance of Listeria monocytogenes against Food Antimicrobials and Cross-Protection Induced by Exposure to Organic Acid Salts

Kang

Wiedmann

Boor

et al. 2015

Appl Environ Microbiol

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Formulations of ready-to-eat (RTE) foods with antimicrobial compounds constitute an important safety measure against foodborne pathogens such as Listeria monocytogenes. While the efficacy of many commercially available antimicrobial compounds has been demonstrated in a variety of foods, the current understanding of the resistance mechanisms employed by L. monocytogenes to counteract these stresses is limited. In this study, we screened in-frame deletion mutants of two-component system response regulators associated with the cell envelope stress response for increased sensitivity to commercially available antimicrobial compounds (nisin, lauric arginate, -polylysine, and chitosan). A virR deletion mutant showed increased sensitivity to all antimicrobials and significantly greater loss of membrane integrity when exposed to nisin, lauric arginate, or -polylysine (P < 0.05). The VirR-regulated operon, dltABCD, was shown to be the key contributor to resistance against these antimicrobial compounds, whereas another VirR-regulated gene, mprF, displayed an antimicrobial-specific contribution to resistance. An experiment with a ␤-glucuronidase (GUS) reporter fusion with the dlt promoter indicated that nisin does not specifically induce VirRdependent upregulation of dltABCD. Lastly, prior exposure of L. monocytogenes parent strain H7858 and the ⌬virR mutant to 2% potassium lactate enhanced subsequent resistance against nisin and -polylysine (P < 0.05). These data demonstrate that VirRS-mediated regulation of dltABCD is the major resistance mechanism used by L. monocytogenes against cell envelope-damaging food antimicrobials. Further, the potential for cross-protection induced by other food-related stresses (e.g., organic acids) needs to be considered when applying these novel food antimicrobials as a hurdle strategy for RTE foods. Control of Listeria monocytogenes in ready-to-eat (RTE) foods is an important food safety goal due to the high mortality rate associated with listeriosis, particularly in susceptible populations, such as pregnant women, the elderly, and those with a compromised immune system (1). L. monocytogenes is of particular concern for those RTE foods that support growth of this pathogen to high levels during refrigerated storage, which can potentially cause a life-threatening disease. L. monocytogenes harbors a variety of stress coping mechanisms that allow it to survive under suboptimal environmental conditions associated with foods (e.g., acidic, osmotic, and/or temperature stress) (2). The ability of L. monocytogenes to tolerate and grow under such a wide range of adverse conditions elevates the likelihood of foodborne transmission to a human host. Thus, a multipronged approach (e.g., prevention of postprocessing contamination and reformulation of RTE foods with antimicrobials) to limit L. monocytogenes in foods along the farm-to-fork continuum is critical to reduce the potential for foodborne illnesses involving this organism (3).Natural antimicrobials are commonly applied to RTE foods to control foodb...

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