George Nychas | Agricultural University of Athens (original) (raw)
Papers by George Nychas
Frontiers in Microbiology, 2015
A community-based sessile life style is the normal mode of growth and survival for many bacterial... more A community-based sessile life style is the normal mode of growth and survival for many bacterial species. Under such conditions, cell-to-cell interactions are inevitable and ultimately lead to the establishment of dense, complex and highly structured biofilm populations encapsulated in a self-produced extracellular matrix and capable of coordinated and collective behavior. Remarkably, in food processing environments, a variety of different bacteria may attach to surfaces, survive, grow, and form biofilms. Salmonella enterica, Listeria monocytogenes, Escherichia coli, and Staphylococcus aureus are important bacterial pathogens commonly implicated in outbreaks of foodborne diseases, while all are known to be able to create biofilms on both abiotic and biotic surfaces. Particularly challenging is the attempt to understand the complexity of inter-bacterial interactions that can be encountered in such unwanted consortia, such as competitive and cooperative ones, together with their impact on the final outcome of these communities (e.g., maturation, physiology, antimicrobial resistance, virulence, dispersal). In this review, up-to-date data on both the intra- and inter-species interactions encountered in biofilms of these pathogens are presented. A better understanding of these interactions, both at molecular and biophysical levels, could lead to novel intervention strategies for controlling pathogenic biofilm formation in food processing environments and thus improve food safety.
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The Journal of applied bacteriology, 1993
The presence of low concentrations (0.1% w/v) of oleuropein, a phenolic compound extracted from o... more The presence of low concentrations (0.1% w/v) of oleuropein, a phenolic compound extracted from olives, delayed the growth of Staphylococcus aureus in NZ amine A and brain heart infusion media modified by the addition of growth factors and glucose (NZA+ and BHI+), as indicated by changes in conductance, whilst higher concentrations (0.4-0.6% w/v) inhibited growth completely. Intermediate concentrations of oleuropein (0.2%) prevented growth in BHI+ but allowed growth to occur in NZA+ despite an extended lag phase (30 h). Concentrations of oleuropein > 0.2% inhibited growth and production of enterotoxin B in both types of media. Lower levels (0.1%) did not affect the final viable count and production of toxin in BHI+ but decreased the number of viable organisms and reduced the toxin production in NZA+ by eightfold. An increase in the concentration of oleuropein resulted in a decrease in the amount of glucose assimilated and consequently the amount of lactate produced. In addition, ...
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Journal of Applied Bacteriology, 1991
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Meat Science, 2012
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The 2010 International Joint Conference on Neural Networks (IJCNN), 2010
Abstract The development of accurate models to describe and predict pressure inactivation kinetic... more Abstract The development of accurate models to describe and predict pressure inactivation kinetics of microorganisms is very beneficial to the food industry for optimization of process conditions. The need for intelligent methods to model highly nonlinear systems is long ...
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Journal of Applied Bacteriology, 1995
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Meat Science, 2007
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Meat Science, 2009
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Letters in Applied Microbiology, 2002
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Letters in Applied Microbiology, 1990
... growth of Staph. aureus in static cultures was markedly influ-enced by the composition of the... more ... growth of Staph. aureus in static cultures was markedly influ-enced by the composition of the growth medium. NZA medium was invariably superior to BHI when judged by cell proliferation and protein secretion. In practice, the ...
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Journal of Food Science, 2013
This study evaluated growth of Listeria monocytogenes inoculated on cooked chicken meat with diff... more This study evaluated growth of Listeria monocytogenes inoculated on cooked chicken meat with different marinades and survival of the pathogen as affected by microwave oven reheating. During aerobic storage at 7 °C, on days 0, 1, 2, 4, and 7, samples were reheated by microwave oven (1100 W) for 45 or 90 s and analyzed microbiologically. L. monocytogenes counts on nonmarinated (control) samples increased (P < 0.05) from 2.7 ± 0.1 (day-0) to 6.9 ± 0.1 (day-7) log CFU/g during storage. Initial (day-0) pathogen counts of marinated samples were <0.5 log CFU/g lower than those of the control, irrespective of marinating treatment. At 7 d of storage, pathogen levels on samples marinated with tomato juice were not different (P ≥ 0.05; 6.9 ± 0.1 log CFU/g) from those of the control, whereas for samples treated with the remaining marinades, pathogen counts were 0.7 (soy sauce) to 2.0 (lemon juice) log CFU/g lower (P < 0.05) than those of the control. Microwave oven reheating reduced L. monocytogenes counts by 1.9 to 4.1 (45 s) and >2.4 to 5.0 (90 s) log CFU/g. With similar trends across different marinates, the high levels of L. monocytogenes survivors found after microwave reheating, especially after storage for more than 2 d, indicate that length of storage and reheating time need to be considered for safe consumption of leftover cooked chicken.
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Journal of Applied Microbiology, 2001
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International Journal of Food Science & Technology, 2007
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International Journal of Food Microbiology, 2014
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International Journal of Food Microbiology, 2011
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International Journal of Food Microbiology, 2011
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International Journal of Food Microbiology, 2011
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International Journal of Food Microbiology, 1996
Glucose was added to minced meat (pH 6.0) and stored under aerobic or a modified atmosphere (MA) ... more Glucose was added to minced meat (pH 6.0) and stored under aerobic or a modified atmosphere (MA) composed of 80% O2 and 20% CO2 to assess the effects of carbohydrate on the microbial association and the chemical properties of the meat. The type of packaging affected the size and the final composition of the microflora. The microbial composition of the mince without added glucose in air or MA, given in log10 cfu/g respectively, were pseudomonads (9.8 and 7.3), Brochothrix thermosphacta (8.5 and 8.1), lactic acid bacteria (8.8 and 8.7), Enterobacteriaceae (7.2 and 6.1) and yeasts (4.3 and 4.2). In mince supplemented with 0.2% (w/w) glucose, similar composition and numbers were observed. Glucose, glucose 6-phosphate and lactic acid were consumed at slower rates by the flora on meat stored under MA than by the flora on meat stored in air. The addition of glucose enhanced gluconate production by the flora on meat stored in air. D-lactic and acetic acid were produced in all samples stored under the MA.
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International Journal of Food Microbiology, 2009
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International Journal of Food Microbiology, 2005
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Frontiers in Microbiology, 2015
A community-based sessile life style is the normal mode of growth and survival for many bacterial... more A community-based sessile life style is the normal mode of growth and survival for many bacterial species. Under such conditions, cell-to-cell interactions are inevitable and ultimately lead to the establishment of dense, complex and highly structured biofilm populations encapsulated in a self-produced extracellular matrix and capable of coordinated and collective behavior. Remarkably, in food processing environments, a variety of different bacteria may attach to surfaces, survive, grow, and form biofilms. Salmonella enterica, Listeria monocytogenes, Escherichia coli, and Staphylococcus aureus are important bacterial pathogens commonly implicated in outbreaks of foodborne diseases, while all are known to be able to create biofilms on both abiotic and biotic surfaces. Particularly challenging is the attempt to understand the complexity of inter-bacterial interactions that can be encountered in such unwanted consortia, such as competitive and cooperative ones, together with their impact on the final outcome of these communities (e.g., maturation, physiology, antimicrobial resistance, virulence, dispersal). In this review, up-to-date data on both the intra- and inter-species interactions encountered in biofilms of these pathogens are presented. A better understanding of these interactions, both at molecular and biophysical levels, could lead to novel intervention strategies for controlling pathogenic biofilm formation in food processing environments and thus improve food safety.
Bookmarks Related papers MentionsView impact
The Journal of applied bacteriology, 1993
The presence of low concentrations (0.1% w/v) of oleuropein, a phenolic compound extracted from o... more The presence of low concentrations (0.1% w/v) of oleuropein, a phenolic compound extracted from olives, delayed the growth of Staphylococcus aureus in NZ amine A and brain heart infusion media modified by the addition of growth factors and glucose (NZA+ and BHI+), as indicated by changes in conductance, whilst higher concentrations (0.4-0.6% w/v) inhibited growth completely. Intermediate concentrations of oleuropein (0.2%) prevented growth in BHI+ but allowed growth to occur in NZA+ despite an extended lag phase (30 h). Concentrations of oleuropein > 0.2% inhibited growth and production of enterotoxin B in both types of media. Lower levels (0.1%) did not affect the final viable count and production of toxin in BHI+ but decreased the number of viable organisms and reduced the toxin production in NZA+ by eightfold. An increase in the concentration of oleuropein resulted in a decrease in the amount of glucose assimilated and consequently the amount of lactate produced. In addition, ...
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Journal of Applied Bacteriology, 1991
Bookmarks Related papers MentionsView impact
Meat Science, 2012
Bookmarks Related papers MentionsView impact
The 2010 International Joint Conference on Neural Networks (IJCNN), 2010
Abstract The development of accurate models to describe and predict pressure inactivation kinetic... more Abstract The development of accurate models to describe and predict pressure inactivation kinetics of microorganisms is very beneficial to the food industry for optimization of process conditions. The need for intelligent methods to model highly nonlinear systems is long ...
Bookmarks Related papers MentionsView impact
Journal of Applied Bacteriology, 1995
Bookmarks Related papers MentionsView impact
Meat Science, 2007
Bookmarks Related papers MentionsView impact
Meat Science, 2009
Bookmarks Related papers MentionsView impact
Letters in Applied Microbiology, 2002
Bookmarks Related papers MentionsView impact
Letters in Applied Microbiology, 1990
... growth of Staph. aureus in static cultures was markedly influ-enced by the composition of the... more ... growth of Staph. aureus in static cultures was markedly influ-enced by the composition of the growth medium. NZA medium was invariably superior to BHI when judged by cell proliferation and protein secretion. In practice, the ...
Bookmarks Related papers MentionsView impact
Journal of Food Science, 2013
This study evaluated growth of Listeria monocytogenes inoculated on cooked chicken meat with diff... more This study evaluated growth of Listeria monocytogenes inoculated on cooked chicken meat with different marinades and survival of the pathogen as affected by microwave oven reheating. During aerobic storage at 7 °C, on days 0, 1, 2, 4, and 7, samples were reheated by microwave oven (1100 W) for 45 or 90 s and analyzed microbiologically. L. monocytogenes counts on nonmarinated (control) samples increased (P < 0.05) from 2.7 ± 0.1 (day-0) to 6.9 ± 0.1 (day-7) log CFU/g during storage. Initial (day-0) pathogen counts of marinated samples were <0.5 log CFU/g lower than those of the control, irrespective of marinating treatment. At 7 d of storage, pathogen levels on samples marinated with tomato juice were not different (P ≥ 0.05; 6.9 ± 0.1 log CFU/g) from those of the control, whereas for samples treated with the remaining marinades, pathogen counts were 0.7 (soy sauce) to 2.0 (lemon juice) log CFU/g lower (P < 0.05) than those of the control. Microwave oven reheating reduced L. monocytogenes counts by 1.9 to 4.1 (45 s) and >2.4 to 5.0 (90 s) log CFU/g. With similar trends across different marinates, the high levels of L. monocytogenes survivors found after microwave reheating, especially after storage for more than 2 d, indicate that length of storage and reheating time need to be considered for safe consumption of leftover cooked chicken.
Bookmarks Related papers MentionsView impact
Journal of Applied Microbiology, 2001
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International Journal of Food Science & Technology, 2007
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International Journal of Food Microbiology, 2014
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International Journal of Food Microbiology, 2011
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International Journal of Food Microbiology, 2011
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International Journal of Food Microbiology, 2011
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International Journal of Food Microbiology, 1996
Glucose was added to minced meat (pH 6.0) and stored under aerobic or a modified atmosphere (MA) ... more Glucose was added to minced meat (pH 6.0) and stored under aerobic or a modified atmosphere (MA) composed of 80% O2 and 20% CO2 to assess the effects of carbohydrate on the microbial association and the chemical properties of the meat. The type of packaging affected the size and the final composition of the microflora. The microbial composition of the mince without added glucose in air or MA, given in log10 cfu/g respectively, were pseudomonads (9.8 and 7.3), Brochothrix thermosphacta (8.5 and 8.1), lactic acid bacteria (8.8 and 8.7), Enterobacteriaceae (7.2 and 6.1) and yeasts (4.3 and 4.2). In mince supplemented with 0.2% (w/w) glucose, similar composition and numbers were observed. Glucose, glucose 6-phosphate and lactic acid were consumed at slower rates by the flora on meat stored under MA than by the flora on meat stored in air. The addition of glucose enhanced gluconate production by the flora on meat stored in air. D-lactic and acetic acid were produced in all samples stored under the MA.
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International Journal of Food Microbiology, 2009
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International Journal of Food Microbiology, 2005
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