Campylobacter jejuni is the world's leading foodborne bacterial pathogen of gastrointestinal ... more Campylobacter jejuni is the world's leading foodborne bacterial pathogen of gastrointestinal disease in humans. C. jejuni is a fastidious but widespread organism and the most frequently reported zoonotic pathogen in the European Union since 2005. This led us to believe that C. jejuni , which is highly sensitive to stress factors (starvation and oxygen concentration) and has a low growth rate, benefits significantly from the luxS gene.
To define anti‐Campylobacter jejuni activity of an extract from waste skins and seeds of Pinot no... more To define anti‐Campylobacter jejuni activity of an extract from waste skins and seeds of Pinot noir grapes (GSS), resveratrol and possible resistance mechanisms, and the influence of these on Camp. jejuni morphology.
International Journal of Food Properties, Nov 2, 2012
The phenolic composition, antioxidant and antimicrobial activity of extracts from vine leaves of ... more The phenolic composition, antioxidant and antimicrobial activity of extracts from vine leaves of six grape varieties collected in May, August and September was studied. The phenolic potential of the extracts was dependent on variety and picking-time. Extracts of leaves collected in September were the richest in total phenols, flavonoids, flavonols and stilbenes. The antioxidant properties determined by FRAP and DPPH assays, and antimicrobial activity against Stapylococcus aureus, Bacillus cereus, Campylobacter jejuni, Escherichia coli and Salmonella Infantis were good and in correlation with the chemical composition changes of the leaf extracts. The results indicated that leaves remaining on the vine in September after grape harvest could be especially promising as an inexpensive source of effective antioxidant/antimicrobial agents.
Phenolic plant extracts are sources of natural bioactive compounds, which can inhibit the rate of... more Phenolic plant extracts are sources of natural bioactive compounds, which can inhibit the rate of food spoilage. MIC and MBC concentrations of four oil- or water-soluble rosemary (Rosmarinus officinalis) extracts against gram-positive (Bacillus and Staphylococcus) and gram-negative (Campylobacter and Salmonella) bacteria were determined by using disk diffusion, agar dilution, and broth microdilution methods, as well as bacterial survival kinetics in a macrodilution test. To describe the antioxidant properties of the extracts, the reducing power, free radical scavenging effectiveness, and β-carotene bleaching test were used. The antimicrobial and antioxidant activity depended on the concentration and chemical nature of the phenolic compounds in the extracts. Gram-positive bacteria were more sensitive than were gram-negative bacteria, especially for oil-soluble extracts with carnosic acid as the major phenolic compound. A microdilution method based on ATP measurement was found to be a useful, rapid technique for determining antibacterial efficiency, and its results correlated well with MICs from survival curve measurement. Reducing power and free radical scavenging effectiveness was higher in water-soluble formulations, according to their higher total phenolic content, but in an aqueous emulsion system of linoleic acid, they exhibited lower antioxidant activity. This correlated well with the higher efficiency of antimicrobial activity of oil-soluble formulations, despite the lower total phenolic content of these extracts.
International Journal of Food Microbiology, Sep 1, 2021
Predictive microbiology methods were used to study the effect of carvacrol on the bacterial resis... more Predictive microbiology methods were used to study the effect of carvacrol on the bacterial resistance to antimicrobials. Our objective was to estimate the optimum dose of carvacrol at concentrations below its MIC value (Minimum Inhibitory Concentration). As a fluorescent marker, ethidium bromide (EtBr) was applied to Escherichia coli to acquire raw data. The accumulation of EtBr was measured by its fluorescence signal (Fs), in the unit of RFU (Relative Fluorescence Unit). The temporal change of the fluorescence values, at a constant concentration of carvacrol, was described by a saturation curve (primary model). The difference, within the observation interval, between the fitted initial and maximum fluorescent values was chosen as the primary parameter to be fitted in the secondary model: a convex, asymmetric, bi-linear function of the carvacrol concentration changing between 0 and 0.5 MIC. Its breakpoint is the optimum value of the carvacrol, a cardinal parameter of the secondary model, where the chosen primary parameter assumes its highest value. This optimum was estimated with high uncertainty for individual experiments, but F-test showed that, with appropriate experimental and numerical procedure, its existence and value can be claimed with confidence. Our results demonstrate that the estimation of the optimum of the secondary model can be robust even if the full secondary model is uncertain.
The purpose of this study was the genotypic and phenotypic characterization of 57 strains of Stap... more The purpose of this study was the genotypic and phenotypic characterization of 57 strains of Staphylococcus epidermidis isolated from cleanroom environments, based on their biofilm formation and antimicrobial resistance profiles.
Abstract: Campylobacters, gram negative spiral shaped, microaerophylic and termophilic bacteria, ... more Abstract: Campylobacters, gram negative spiral shaped, microaerophylic and termophilic bacteria, counter several survival strategies which contribute to their persistence and spreading in the environment. These bacteria cause food-borne illnesses worldwide due ...
ABSTRACTObjective: Research into Campylobacter jejuni pathogenesis and host responses to C. jejun... more ABSTRACTObjective: Research into Campylobacter jejuni pathogenesis and host responses to C. jejuni infection is needed in the fight against human campylobacteriosis.Methods: We established intravenous infections of BALB/c mice with either a C. jejuni food isolate or C. jejuni of human origin. Further we include PCR to demonstrate the presence and stability of the putative virulence genes cadF, virbB11, cdtB, cdtC, ceuE in C. jejuni isolates and we examined cytokine production of IL-6, IL-12, TNF-α, IFN-γ, IL-10 in the livers of these infected mice.Results: We confirm here the presence of the cadF, cdtB, cdtC and ceuE genes in a food and a clinical C. jejuni isolate, with no sequence changes after the C. jejuni sub-culturing in a food model and when recovered from mouse liver after infection. Both of these C. jejuni isolates persisted in the mouse livers and activated comparable cytokine patterns for IL-12, TNF-α, IFN-γ and IL-10, with down-regulation of IL-6.Conclusions: These data show the comparability of these C. jejuni food and clinical isolates in terms of the prevalence and stability of their putative virulence genes and the outcome of disease during systemic murine campylobacteriosis.
Predictive microbiology methods were used to study the effect of carvacrol on the bacterial resis... more Predictive microbiology methods were used to study the effect of carvacrol on the bacterial resistance to antimicrobials. Our objective was to estimate the optimum dose of carvacrol at concentrations below its MIC value (Minimum Inhibitory Concentration). As a fluorescent marker, ethidium bromide (EtBr) was applied to Escherichia coli to acquire raw data. The accumulation of EtBr was measured by its fluorescence signal (Fs), in the unit of RFU (Relative Fluorescence Unit). The temporal change of the fluorescence values, at a constant concentration of carvacrol, was described by a saturation curve (primary model). The difference, within the observation interval, between the fitted initial and maximum fluorescent values was chosen as the primary parameter to be fitted in the secondary model: a convex, asymmetric, bi-linear function of the carvacrol concentration changing between 0 and 0.5 MIC. Its breakpoint is the optimum value of the carvacrol, a cardinal parameter of the secondary model, where the chosen primary parameter assumes its highest value. This optimum was estimated with high uncertainty for individual experiments, but F-test showed that, with appropriate experimental and numerical procedure, its existence and value can be claimed with confidence. Our results demonstrate that the estimation of the optimum of the secondary model can be robust even if the full secondary model is uncertain.
Listeria innocua is genetically closely related to the foodborne human pathogen Listeria monocyto... more Listeria innocua is genetically closely related to the foodborne human pathogen Listeria monocytogenes. However, as most L. innocua strains are non-pathogenic, it has been proposed as a surrogate organism for determining the efficacy of antimicrobial strategies against L. monocytogenes. Teichoic acids are one of the three major cell wall components of Listeria, along with the peptidoglycan backbone and cell wall-associated proteins. The polymeric teichoic acids make up the majority of cell wall carbohydrates; the type of teichoic acids directly attached to the peptidoglycan are termed wall teichoic acids (WTAs). WTAs play vital physiological roles, are important virulence factors, antigenic determinants, and phage-binding ligands. The structures of the various WTAs of L. monocytogenes are well known, whereas those of L. innocua are not. In the present study, the WTA structure of L. innocua ŽM39 was determined mainly by 1D and 2D NMR spectroscopy and it was found to be the following: [→4)-[α-D-GlcpNAc-(1→3)]-β-D-GlcpNAc-(1→4)-D-Rbo-(1P→]n This structure is new with respect to all currently known Listeria WTAs and it shares structural similarities with type II WTA serovar 6a. In addition, the genome of strain L. innocua ŽM39 was sequenced and the majority of putative WTA synthesis genes were identified.
Campylobacter jejuni is the world's leading foodborne bacterial pathogen of gastrointestinal ... more Campylobacter jejuni is the world's leading foodborne bacterial pathogen of gastrointestinal disease in humans. C. jejuni is a fastidious but widespread organism and the most frequently reported zoonotic pathogen in the European Union since 2005. This led us to believe that C. jejuni , which is highly sensitive to stress factors (starvation and oxygen concentration) and has a low growth rate, benefits significantly from the luxS gene.
To define anti‐Campylobacter jejuni activity of an extract from waste skins and seeds of Pinot no... more To define anti‐Campylobacter jejuni activity of an extract from waste skins and seeds of Pinot noir grapes (GSS), resveratrol and possible resistance mechanisms, and the influence of these on Camp. jejuni morphology.
International Journal of Food Properties, Nov 2, 2012
The phenolic composition, antioxidant and antimicrobial activity of extracts from vine leaves of ... more The phenolic composition, antioxidant and antimicrobial activity of extracts from vine leaves of six grape varieties collected in May, August and September was studied. The phenolic potential of the extracts was dependent on variety and picking-time. Extracts of leaves collected in September were the richest in total phenols, flavonoids, flavonols and stilbenes. The antioxidant properties determined by FRAP and DPPH assays, and antimicrobial activity against Stapylococcus aureus, Bacillus cereus, Campylobacter jejuni, Escherichia coli and Salmonella Infantis were good and in correlation with the chemical composition changes of the leaf extracts. The results indicated that leaves remaining on the vine in September after grape harvest could be especially promising as an inexpensive source of effective antioxidant/antimicrobial agents.
Phenolic plant extracts are sources of natural bioactive compounds, which can inhibit the rate of... more Phenolic plant extracts are sources of natural bioactive compounds, which can inhibit the rate of food spoilage. MIC and MBC concentrations of four oil- or water-soluble rosemary (Rosmarinus officinalis) extracts against gram-positive (Bacillus and Staphylococcus) and gram-negative (Campylobacter and Salmonella) bacteria were determined by using disk diffusion, agar dilution, and broth microdilution methods, as well as bacterial survival kinetics in a macrodilution test. To describe the antioxidant properties of the extracts, the reducing power, free radical scavenging effectiveness, and β-carotene bleaching test were used. The antimicrobial and antioxidant activity depended on the concentration and chemical nature of the phenolic compounds in the extracts. Gram-positive bacteria were more sensitive than were gram-negative bacteria, especially for oil-soluble extracts with carnosic acid as the major phenolic compound. A microdilution method based on ATP measurement was found to be a useful, rapid technique for determining antibacterial efficiency, and its results correlated well with MICs from survival curve measurement. Reducing power and free radical scavenging effectiveness was higher in water-soluble formulations, according to their higher total phenolic content, but in an aqueous emulsion system of linoleic acid, they exhibited lower antioxidant activity. This correlated well with the higher efficiency of antimicrobial activity of oil-soluble formulations, despite the lower total phenolic content of these extracts.
International Journal of Food Microbiology, Sep 1, 2021
Predictive microbiology methods were used to study the effect of carvacrol on the bacterial resis... more Predictive microbiology methods were used to study the effect of carvacrol on the bacterial resistance to antimicrobials. Our objective was to estimate the optimum dose of carvacrol at concentrations below its MIC value (Minimum Inhibitory Concentration). As a fluorescent marker, ethidium bromide (EtBr) was applied to Escherichia coli to acquire raw data. The accumulation of EtBr was measured by its fluorescence signal (Fs), in the unit of RFU (Relative Fluorescence Unit). The temporal change of the fluorescence values, at a constant concentration of carvacrol, was described by a saturation curve (primary model). The difference, within the observation interval, between the fitted initial and maximum fluorescent values was chosen as the primary parameter to be fitted in the secondary model: a convex, asymmetric, bi-linear function of the carvacrol concentration changing between 0 and 0.5 MIC. Its breakpoint is the optimum value of the carvacrol, a cardinal parameter of the secondary model, where the chosen primary parameter assumes its highest value. This optimum was estimated with high uncertainty for individual experiments, but F-test showed that, with appropriate experimental and numerical procedure, its existence and value can be claimed with confidence. Our results demonstrate that the estimation of the optimum of the secondary model can be robust even if the full secondary model is uncertain.
The purpose of this study was the genotypic and phenotypic characterization of 57 strains of Stap... more The purpose of this study was the genotypic and phenotypic characterization of 57 strains of Staphylococcus epidermidis isolated from cleanroom environments, based on their biofilm formation and antimicrobial resistance profiles.
Abstract: Campylobacters, gram negative spiral shaped, microaerophylic and termophilic bacteria, ... more Abstract: Campylobacters, gram negative spiral shaped, microaerophylic and termophilic bacteria, counter several survival strategies which contribute to their persistence and spreading in the environment. These bacteria cause food-borne illnesses worldwide due ...
ABSTRACTObjective: Research into Campylobacter jejuni pathogenesis and host responses to C. jejun... more ABSTRACTObjective: Research into Campylobacter jejuni pathogenesis and host responses to C. jejuni infection is needed in the fight against human campylobacteriosis.Methods: We established intravenous infections of BALB/c mice with either a C. jejuni food isolate or C. jejuni of human origin. Further we include PCR to demonstrate the presence and stability of the putative virulence genes cadF, virbB11, cdtB, cdtC, ceuE in C. jejuni isolates and we examined cytokine production of IL-6, IL-12, TNF-α, IFN-γ, IL-10 in the livers of these infected mice.Results: We confirm here the presence of the cadF, cdtB, cdtC and ceuE genes in a food and a clinical C. jejuni isolate, with no sequence changes after the C. jejuni sub-culturing in a food model and when recovered from mouse liver after infection. Both of these C. jejuni isolates persisted in the mouse livers and activated comparable cytokine patterns for IL-12, TNF-α, IFN-γ and IL-10, with down-regulation of IL-6.Conclusions: These data show the comparability of these C. jejuni food and clinical isolates in terms of the prevalence and stability of their putative virulence genes and the outcome of disease during systemic murine campylobacteriosis.
Predictive microbiology methods were used to study the effect of carvacrol on the bacterial resis... more Predictive microbiology methods were used to study the effect of carvacrol on the bacterial resistance to antimicrobials. Our objective was to estimate the optimum dose of carvacrol at concentrations below its MIC value (Minimum Inhibitory Concentration). As a fluorescent marker, ethidium bromide (EtBr) was applied to Escherichia coli to acquire raw data. The accumulation of EtBr was measured by its fluorescence signal (Fs), in the unit of RFU (Relative Fluorescence Unit). The temporal change of the fluorescence values, at a constant concentration of carvacrol, was described by a saturation curve (primary model). The difference, within the observation interval, between the fitted initial and maximum fluorescent values was chosen as the primary parameter to be fitted in the secondary model: a convex, asymmetric, bi-linear function of the carvacrol concentration changing between 0 and 0.5 MIC. Its breakpoint is the optimum value of the carvacrol, a cardinal parameter of the secondary model, where the chosen primary parameter assumes its highest value. This optimum was estimated with high uncertainty for individual experiments, but F-test showed that, with appropriate experimental and numerical procedure, its existence and value can be claimed with confidence. Our results demonstrate that the estimation of the optimum of the secondary model can be robust even if the full secondary model is uncertain.
Listeria innocua is genetically closely related to the foodborne human pathogen Listeria monocyto... more Listeria innocua is genetically closely related to the foodborne human pathogen Listeria monocytogenes. However, as most L. innocua strains are non-pathogenic, it has been proposed as a surrogate organism for determining the efficacy of antimicrobial strategies against L. monocytogenes. Teichoic acids are one of the three major cell wall components of Listeria, along with the peptidoglycan backbone and cell wall-associated proteins. The polymeric teichoic acids make up the majority of cell wall carbohydrates; the type of teichoic acids directly attached to the peptidoglycan are termed wall teichoic acids (WTAs). WTAs play vital physiological roles, are important virulence factors, antigenic determinants, and phage-binding ligands. The structures of the various WTAs of L. monocytogenes are well known, whereas those of L. innocua are not. In the present study, the WTA structure of L. innocua ŽM39 was determined mainly by 1D and 2D NMR spectroscopy and it was found to be the following: [→4)-[α-D-GlcpNAc-(1→3)]-β-D-GlcpNAc-(1→4)-D-Rbo-(1P→]n This structure is new with respect to all currently known Listeria WTAs and it shares structural similarities with type II WTA serovar 6a. In addition, the genome of strain L. innocua ŽM39 was sequenced and the majority of putative WTA synthesis genes were identified.
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