Attachment of Salmonella Poona to Cantaloupe Rind and Stem Scar Tissues as Affected by Temperature of Fruit and Inoculum

2004 ◽  
Vol 67 (7) ◽  
pp. 1359-1364 ◽  
Author(s):  
GLENNER M. RICHARDS ◽  
LARRY R. BEUCHAT
Keyword(s):  
Salmonella Enterica ◽  
Negative Temperature ◽  
Wash Water ◽  
Weight Increase ◽  
Effect Of Temperature ◽  
Temperature Differential

A negative temperature differential between fruits or vegetables and the water in which they are immersed theoretically enhances infiltration of water and any microorganisms it might contain into tissues. The effect of temperature differentials between cantaloupes and wash water, each at 4 and 30°C, on changes in cantaloupe weight and populations of Salmonella enterica Poona recovered from rinds and stem scar tissues of Eastern and Western (shipper) types of cantaloupes was assessed. The percent weight increase in Western cantaloupes was significantly greater (P ≤ 0.05) than that in Eastern cantaloupes for all cantaloupe and inoculum temperature combinations. Salmonella Poona attachment to or infiltration of Eastern but not Western cantaloupe rind is enhanced when the fruit is at 4°C, compared with 30°C, regardless of the temperature of the immersion suspension. The number of Salmonella Poona cells recovered from rind tissue of Western cantaloupes at 30°C immersed in inoculum at 30°C was significantly less (P ≤ 0.05) than that recovered from rind tissues of cantaloupes at 4 or 30°C that were immersed in inoculum at 4°C. Salmonella Poona in immersion water can adhere to or infiltrate surface tissues of cantaloupes. The populations of Salmonella Poona recovered from stem scar tissues of Eastern and Western types of cantaloupes were not significantly (P > 0.05) affected by cantaloupe and inoculum temperature combinations. Populations of cells adhering to or infiltrating various cantaloupe tissues is not dictated entirely by temperature differentials between fruits and immersion suspensions; rather, it also apparently is influenced by structures unique to surface tissues.

Postharvest Handling Conditions Affect Internalization of Salmonella in Baby Spinach during Washing

2013 ◽  
Vol 76 (7) ◽  
pp. 1145-1151 ◽  
Author(s):  
VICENTE M. GÓMEZ-LÓPEZ ◽  
ALICIA MARÍN ◽  
ANA ALLENDE ◽  
LARRY R. BEUCHAT ◽  
MARÍA I. GIL
Keyword(s):  
Green Fluorescent Protein ◽  
Laser Scanning ◽  
Fluorescent Protein ◽  
Negative Temperature ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Temperature Differential ◽  
Postharvest Handling ◽  
Green Fluorescent ◽  
Spinach Leaves

Internalization of foodborne pathogens in fruits and vegetables is an increasing safety concern. The aim of this research was to assess the potential for internalization of an enteric pathogen (Salmonella enterica serotype Typhimurium) in a leafy vegetable (baby spinach) during washing as influenced by three postharvest handling conditions: (i) illumination, (ii) negative temperature differential, and (iii) relative humidity (RH). To compare these potential postharvest handling conditions, leaves were exposed to different levels of illumination (0, 1,000, and 2,000 lx), temperature differential (5, 11, 14, 20, and 26uC), and RH (99, 85, and 74%) for a short time before or during washing. Washing of baby spinach was carried out in water containing green fluorescent protein–tagged Salmonella Typhimurium (6.5 log CFU/ml) at 5uC for 2 min, followed by surface disinfection with chlorine (10,000 μg/ml) for 1 min, two rinses in water for 10 s, and spin drying for 15 s. Internalization was assessed by enumerating the pathogen on Salmonella-Shigella agar and by confocal laser scanning microscopy. Illumination of spinach leaves before and during washing and a negative temperature differential during washing did not significantly (P > 0.05) increase the number of internalized bacteria. However, exposure of leaves to low-RH conditions before washing, which reduced the tissue water content, decreased internalization of Salmonella compared with internalization in baby spinach exposed to high RH (P ≤ 0.05). Green fluorescent protein–tagged Salmonella Typhimurium was visualized by confocal laser scanning microscopy at a depth of up to 30 μm beneath the surface of spinach leaves after exposure to a high inoculum level (8 log CFU/ml) for an extended time (2 h). Results show that internalization of Salmonella into baby spinach leaves can occur but can be minimized under specific postharvest handling conditions such as low RH.

scholarly journals THE EFFECT OF TEMPERATURE AND OF LYSIN CONCENTRATION ON THE ACCELERATION OF HEMOLYSIS

1941 ◽  
Vol 25 (2) ◽  
pp. 247-261
Author(s):  
Eric Ponder
Keyword(s):  
Cell Surface ◽  
Quantitative Description ◽  
Negative Temperature ◽  
Effect Of Temperature ◽  
Membrane Component ◽  
Temperature Coefficients ◽  
Rate Of Escape ◽  
Point To Point ◽  
Special Case ◽  
Do So

The acceleration of saponin hemolysis by benzene, indol, and nonyl alcohol has been investigated as a function of temperature, and it has been found that these accelerators have negative temperature coefficients. This points to their being concentrated at the cell surface, and to the surface being the seat of their accelerating action. It is shown that the accelerating power of indol (used as a typical accelerator) is constant so long as the lysin in the system is capable of producing lysis per se, but that the acceleration falls off when only sublytic concentrations are present. The relations are expressed in a series of equations, and explained in terms of the reactions among the accelerator, the lysin, and the membrane component, which breaks down in spots, rather than uniformly, when lysis occurs. The argument involves a consideration of the idea that a monolayer of lysin at the cell surface is necessary for hemolysis, of Abramson's hypothesis of "key spots" on the surface, of the rate of escape of hemoglobin from the hemolyzing cell, and of the results of electrophoretic and impedance measurements. The existing theory of the kinetics is extended by introducing the idea of a variation in resistance from point to point in the cell membrane; in this form it describes the situation so far as is at present known, and shows that the results of the various methods of investigation are consistent with each other. The only idea discussed which seems to have little foundation is that lysis is determined by the formation of a monolayer of lysin at the cell surface; when this occurs, it must do so only as a special case. Finally, a semi-quantitative description of the frequency distribution of the resistances in the membrane is derived from existing data. The variation in resistance which it is necessary to assume is quite small, as might be expected in the case of a membrane with a regular ultra-structure.

Effects of Tomato Variety, Temperature Differential, and Post–Stem Removal Time on Internalization of Salmonella Enterica Serovar Thompson in Tomatoes†

2012 ◽  
Vol 75 (2) ◽  
pp. 297-303 ◽  
Author(s):  
XIAODONG XIA ◽  
YAGUANG LUO ◽  
YANG YANG ◽  
BRYAN VINYARD ◽  
KEITH SCHNEIDER ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Tomato Fruit ◽  
Most Probable Number ◽  
Bacterial Suspension ◽  
Time Interval ◽  
Temperature Differential ◽  
Probable Number ◽  
Tomato Variety ◽  
Removal Time ◽  
Tomato Pulp

Tomatoes have been implicated in salmonellosis outbreaks due to possible contamination through bacterial internalization during postharvest handling. This study was conducted to determine the effects of tomato variety, temperature differential between tomato pulp and bacterial suspension, and the time delay between stem removal and immersion in bacterial suspension on internalization of Salmonella enterica serovar Thompson in tomato fruit. Mature green tomatoes at 32.2°C were immersed in water containing approximately 106 CFU/ml S. enterica bacteria. Different tomato varieties (Mountain Spring, Applause, and BHN961), temperature differentials (−10, 0, and 10°F, or −5.6, 0, and 5.6°C, respectively), and post–stem removal times (0, 2, and 16 h) were evaluated for their effects on S. enterica internalization. The incidence and density of internalized cells were determined by culture enrichment and most-probable-number methods, respectively. Overall, variety and post–stem removal time by variety interaction significantly affected the incidence of S. enterica internalization (P < 0.0001), while temperature differential had no significant effect (P = 0.36). Mountain Spring tomatoes were less susceptible to S. enterica internalization than were Applause and BHN961. Increasing the time interval between stem removal and immersion greatly reduced pathogen internalization in BHN961 and Applause, while it had no effect in Mountain Spring tomatoes. The variety and interactions between varieties and post–stem removal times (P = 0.0363) and between temperature differentials and post–stem removal times (P = 0.0257) had significant effects on the populations of internalized S. enterica. Furthermore, all internalized S. enterica cells were found within the core tissue segments immediately underneath the stem scars.

scholarly journals Temperature Correction for FWD Deflection in Cement Pavement Void Detection

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Bei Zhang ◽  
Xiaoliang Wang ◽  
Yanhui Zhong ◽  
Xiaolong Li ◽  
Meimei Hao ◽  
...  
Keyword(s):  
Temperature Difference ◽  
Impact Load ◽  
Three Dimensional ◽  
Field Tests ◽  
Reference Value ◽  
Negative Temperature ◽  
Temperature Correction ◽  
Effect Of Temperature ◽  
Correction Coefficient ◽  
Detection Accuracy

The use of the falling weight deflectometer (FWD) for detecting pavement voids is based on the principle that, under the same impact load, the deflection of pavements with voids increases significantly. Under the effect of temperature, the cement pavement becomes warped, which affects the deflection detection accuracy. In order to improve the accuracy of FWD detection of cement pavement voids, a three-dimensional numerical model of cement pavement on a multilayered elastic foundation under the coupled action of temperature and load is established in this paper. In addition, under different pavement void, climatic, and load conditions, the influence of temperature difference between top and bottom of the plate on the deflection of the center point of plate angle load is studied. Considering the temperature difference between top and bottom, the temperature correction coefficient is established and experimentally verified the accuracy of the temperature correction coefficient. The results showed that, within the ranges of positive and negative temperature differences, the fitting degree of the temperature correction coefficient for the cement pavement exceeded 0.99, which was consistent with the variation trend of the temperature correction coefficient obtained through field tests. The error was lower than 7%, which verified the applicability of the temperature correction coefficient for the dynamic deflection of cement pavements based on FWD. The accuracy of the FWD method in detecting cement pavement voids was improved, and this study demonstrated theoretical reference value and practical engineering significance.

THE EFFECT OF TEMPERATURE DIFFERENTIAL ON THE MOISTURE CONTENT OF STORED WHEAT

1943 ◽  
Vol 21c (10) ◽  
pp. 297-306 ◽  
Author(s):  
J. Ansel Anderson ◽  
J. D. Babbitt ◽  
W. O. S. Meredith
Keyword(s):  
Moisture Content ◽  
Laboratory Experiment ◽  
Water Vapour ◽  
Initial Moisture Content ◽  
Effect Of Temperature ◽  
Western Canada ◽  
Temperature Differential ◽  
Slow Process ◽  
Equilibrium Conditions ◽  
Convective Movement

Local increases in the moisture content of dry wheat stored in country elevator annexes have occasionally been observed in Western Canada. A laboratory experiment suggests that the chief cause is a temperature differential established during the winter. The air in the warmer parts of the grain contains a greater quantity of water vapour than that in the colder, and moisture is transferred either by diffusion or by the convective movement of the air as a whole. A temperature difference of 35 °C, across 6 ft. of grain having an initial moisture content of 14.6%, caused the moisture content at the cold end (0 °C.) to rise to over 20% in 316 days. The experiment indicates that this movement of moisture is a slow process and that equilibrium conditions are never established for any practical length of time or mass of wheat.

scholarly journals Effect of Growth Temperature on Crl-Dependent Regulation of σS Activity in Salmonella enterica Serovar Typhimurium

2008 ◽  
Vol 190 (13) ◽  
pp. 4453-4459 ◽  
Author(s):  
Véronique Robbe-Saule ◽  
Ingrid Carreira ◽  
Annie Kolb ◽  
Françoise Norel
Keyword(s):  
Stationary Phase ◽  
Salmonella Enterica ◽  
Regulatory Protein ◽  
Effect Of Temperature ◽  
Resistance Level ◽  
Serovar Typhimurium ◽  
Negative Effect ◽  
Transcription In Vitro ◽  
Physiological Impact

ABSTRACT The small regulatory protein Crl favors association of the stationary-phase sigma factor σS (RpoS) with the core enzyme polymerase and thereby increases σS activity. Crl has a major physiological impact at low levels of σS. Here, we report that the Crl effects on σS-dependent gene expression, the H2O2 resistance of Salmonella enterica serovar Typhimurium, and the resistance of this organism to acidic pH are greater at 28°C than at 37°C. Immunoblot experiments revealed a negative correlation between σS and Crl levels; the production of Crl was slightly greater at 28°C than at 37°C, whereas the σS levels were about twofold lower at 28°C than at 37°C. At both temperatures, Crl was present in excess of σS, and increasing the Crl level further did not increase the H2O2 resistance level of Salmonella and the expression of the σS-dependent gene katE encoding the stationary-phase catalase. In contrast, increasing the σS level rendered Salmonella more resistant to H2O2 at 28°C, increased the expression of katE, and reduced the magnitude of Crl activation. In addition, the effect of Crl on katE transcription in vitro was not dependent on temperature. These results suggest that the effect of temperature on Crl-dependent regulation of the katE gene and H2O2 resistance are mediated mainly via an effect on σS levels. In addition, our results revealed that σS exerts a negative effect on the production of Crl in stationary phase when the cells contain high levels of σS.

scholarly journals Attachment of Escherichia coli O157:H7 to the Surfaces and Internal Structures of Apples as Detected by Confocal Scanning Laser Microscopy

2000 ◽  
Vol 66 (11) ◽  
pp. 4679-4687 ◽  
Author(s):  
Scott L. Burnett ◽  
Jinru Chen ◽  
Larry R. Beuchat
Keyword(s):  
Escherichia Coli ◽  
Negative Temperature ◽  
Pressure Differential ◽  
Confocal Scanning Laser Microscopy ◽  
Temperature Differential ◽  
E Coli ◽  
Internal Structures ◽  
Scanning Laser Microscopy ◽  
Confocal Scanning ◽  
Confocal Scanning Laser

ABSTRACT Confocal scanning laser microscopy (CSLM) was used to demonstrate the attachment of Escherichia coli O157:H7 transformed with a plasmid encoding for green fluorescent protein (GFP) to the surface and within the internal structures of nonwaxed Red Delicious cv. apples. Apples at 2 or 25°C were inoculated with an E. coli O157:H7 cell suspension at 2 or 25°C. The effect of a negative temperature differential (cold inoculum, warm apple), a positive differential (warm inoculum, cold apple), and no differential (warm inoculum, warm apple), in combination with a pressure differential (atmospheric versus 10,130 Pa), on the attachment and infiltration of cells was determined. CSLM stereo images of external surfaces of apples subjected to all combinations of test parameters showed preferential cellular attachment to discontinuities in the waxy cuticle on the surface and to damaged tissue surrounding puncture wounds, where the pathogen was observed at depths up to 70 μm below the skin surface. Attachment to lenticels was sporadic but was occasionally observed at depths of up to 40 μm. Infiltration through the floral tube and attachment to seeds, cartilaginous pericarp, and internal trichomes were observed in all apples examined, regardless of temperature differential during inoculation. The pressure differential had no effect on infiltration or attachment of E. coliO157:H7. Image analysis to count cells at various depths within tissues was used to quantitatively compare the extent of infiltration into various apple structures as well as the effects of the temperature differential. Puncture wounds harbored greater numbers of the pathogen at greater depths than did other sites examined. Attachment or infiltration of cells was greater on the intact skin and in lenticels, russet areas, and the floral tube of apples inoculated under a negative temperature differential compared to those inoculated under no temperature differential. The results suggest that E. coliO157:H7 attached to internal core structures or within tissues of apples may evade decontamination treatments. Interventions designed to deliver disinfectants to these locations or to remove viable cells ofE. coli O157:H7 and other pathogens from apples by other means need to be developed and validated.

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