Progress 05/01/20 to 07/31/24
Outputs
Target Audience:The project's targeted audience include: - The community of the "International Association of Food Protection," when project results were shared with them during the association's annual meetings. - The egg industry, represented by the Ohio Poultry Association and the American Egg Board. - The scientific community through our publications that revealed new knowledge about the shift in pathogen's virulence when pre-adapted to food's environment. Changes/Problems:The project was completed successfully, and all stated objectives were achieved. What opportunities for training and professional development has the project provided?Under this project, a graduate student (Yumin Xu) received extensive research training. After graduation, the studentwas hired as a research scientist at Abbot Labs.The project also provided advanced training fora doctoral researcher (A. Abdelhamid), who is now an assistant professor at Michigan State University. How have the results been disseminated to communities of interest?The results of the study were effectively disseminated locally and nationally. At the local level, the work was presented at the Ohio State University seminars, and the annual graduate student competitions. Additionally, the work was presented at the annual meetings of the Ohio Valley division of the Institute of Food Technologists. At the national level, the work was presented at the 2020 and 2021 annual meetings of the International Association of Food Protection. The work was also presented at the USDA/NIFA- Food Safety and Defense (A1332) Project Directors' meeting on July 15, 2023, in Toronto, Canada. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
In thefirst phase of the project, experimentswere completed to determine if shell egg heating rate, which varies with different pasteurization implementations, alters the Salmonella enterica serovar Enteritidis response to different stresses or expression of virulence. Shell eggs, containing Salmonella Enteritidis in yolk, were subjected to a low (2.4°C/min) or a high (3.5°C/min) heating rate during treatments that mimicked the pasteurization temperature come-up stage. The low heating rate protected Salmonella from the following processes: (i) lethal heat at the holding stage, (ii) loss of viability during 8-h cooling after heating, and (iii) sequential antimicrobial ozone treatment. Transcriptional analysis using Salmonella reporter strains revealed that the heat stress response gene grpE was transcribed at 3-fold-higher levels (P = 0.0009) at the low than at the high heating rate. Slow heating also significantly increased the transcription of the Salmonella virulence-related genes sopB (P = 0.0012) and sseA (P = 0.0006) in comparison to fast heating. Salmonella virulence was determined experimentally as 50% lethal dose (LD50) values in an in vivo model. The slow heat treatment mildly increased Salmonella Enteritidis virulence in mice (LD50 of 3.3 log CFU), compared to that in nontreated yolk (LD50 of 3.9 log CFU). However, when ozone application followed the slow heat treatment, Salmonella virulence decreased (LD50 of 4.2 log CFU) compared to that for heat-treated or nontreated yolk. In conclusion, heating shell eggs at a low rate can trigger hazardous responses that may compromise the safety of the final pasteurized products but following the thermal treatment with ozone application may help alleviate these concerns. In conclusion, the study demonstrated that slow heating during the pasteurization come-up stage increased the following risks: (i) resistance of Salmonella to pasteurization holding stage or to subsequent ozone treatment, (ii) recovery of Salmonella during the cooling that followed pasteurization, and (iii) Salmonella's ability to cause disease (i.e., virulence). Our findings inform food processors about potential safety risks to consumers resulting from improper use of processing parameters during shell egg pasteurization. Additionally, treating shell eggs with ozone after heat treatment could alleviate these hazards and protect consumers from natural Salmonella Enteritidis contaminants in shell eggs. The second phase of the study was initiated to reveal the relationship between virulence of Salmonella enterica serovar Enteritidis and egg yolk as a hosting medium. Mice were orally challenged with Salmonella Enteritidis cultured in egg yolk or tryptic soy broth (TSB). Additionally, mice were challenged with Salmonella Enteritidis cultured in TSB, followed by administration of sterile egg yolk, to discern the difference between pre-growth of the pathogen and its mere presence in egg yolk during infection. The pathogen's lethal dose 50 (LD50) was the lowest when grown in yolk (2.8×102 CFU), compared to 1.1×103 CFU in TSB, and 4.6×103 CFU in TSB followed by administration of sterile yolk. Additionally, mice that orally received Salmonella Enteritidis grown in egg yolk expressed a high death rate. These findings were supported by transcriptional analysis results. Expression of promoters of virulence-related genes (sopB and sseA) in genetically modified Salmonella Enteritidis reporter strains was significantly higher (p < 0.05) when the bacterium was grown in the yolk, compared to that grown in TSB. Sequencing of RNA (RNA-seq) revealed 204 differentially transcribed genes in Salmonella Enteritidis grown in yolk vs. TSB. Yolk-grown Salmonella Enteritidis exhibited upregulated virulence pathways, including type III secretion systems, epithelial cell invasion, and infection processes; these observations were confirmed by RT-qPCR results. The transcriptomic analysis suggested that upregulation of virulence machinery of Salmonella Enteritidis grown in egg yolk was related to increased iron uptake, biotin utilization, flagellar biosynthesis, and export of virulence proteins encoded on Salmonella pathogenicity island 1, 2, 4, and 5. These biological responses may have acted in concert to increase the virulence of Salmonella infection in mice. In conclusion, growth in egg yolk enhanced Salmonella Enteritidis virulence, indicating the significance of this food vehicle to the risk assessment of salmonellosis. In the final phase of the study,antibiotic-treated mice (i.e., highly sensitive to infection) were used to assess the changes in the virulence ofSalmonellaEnteritidis in shell eggs that were subjected to sublethal heat and heat-ozone treatments. These sublethal processes may be encountered during faulty pasteurization of shell eggs by heat or heat-ozone combination. For sublethal heat treatment, shell eggs were heated slowly to an internal temperature of 42°C. In another experiment, this sublethal heat treatment was combined with a 30-minute ozone exposure. Both treatments were optimized to equalizeSalmonellainoculation levels before testing in streptomycin-treatedC57BL/6 mice.Data analysis indicated that the heat-ozone combination might have acceleratedSalmonellacolonization compared to heat alone on day one post-infection. However, population levels in feces were similar across all groups by day four post-infection. Notably, both treatments (heat alone or heat-ozone combination) potentially increased the virulence ofSalmonella, as evidenced by heightened inflammatory responses in the colon, despite achieving similar colonization rates by day five. This suggests that sublethal egg processing can exasperate the risk ofSalmonellatransmission, since it may enhance pathogen virulence, posing significant safety risks to consumers.In conclusion, these findings underscore the need for careful optimization of egg pasteurization methods to alleviate the potential for increasedSalmonellapathogenicity.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2020
Citation:
Y. XU, A. Abdelhamid, A. Yousef. 2020. Safety of shell eggs as affected by rate of heating during pasteurization to inactivate Salmonella Enteritidis. Annual meeting of the International Association of Food Protection (Abstract P1-152)
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2021
Citation:
Y. Xu, A. Abdelhamid, A. Yousef. 2021. Pathogens turn hypervirulent during colonization of food: Salmonella Enteritidis in egg as an example. Annual meeting of the International Association of Food Protection (Abstract P1-132)
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Progress 05/01/23 to 04/30/24
Outputs
Target Audience:The study targetsegg processors and regulators who aspire to implementa safe and reliable technology to pasteurize shell eggs. The findings of the study will be shared with these targeted audience in various international scientific meetings including the 2024-2025 annual meetings of the International Association of Food Protection. Changes/Problems:No changes were made to the original plan. What opportunities for training and professional development has the project provided?The project was a great chance for advanced training for a post-doctoral researcher and a graduate student. How have the results been disseminated to communities of interest?The results have been presented in Deaprtmental meeting while industrial groups were vising. What do you plan to do during the next reporting period to accomplish the goals?Prepare the new findings for publication in scientific journals.
Impacts
What was accomplished under these goals?
The following summarizes new findings under goal #2: In this phase of research, antibiotic-treated mice (i.e., highly sensitive to infection) were used to assess the changes in the virulence of Salmonella Enteritidis in shell eggs that were subjected to sublethal heat and heat-ozone treatments. These sublethal processes may be encountered during faulty pasteurization of shell eggs by heat or heat-ozone combination. For sublethal heat treatment, shell eggs were heated slowly to an internal temperature of 42°C. In another experiment, this sublethal heat treatment was combined with a 30-minute ozone exposure. Both treatments were optimized to equalize Salmonella inoculation levels before testing in streptomycin-treated C57BL/6 mice.Initial data analysis indicated that the heat-ozone combination might have accelerated Salmonella colonization compared to heat alone on day one post-infection. However, population levels in feces were similar across all groups by day four post-infection. Notably, both treatments (heat alone or heat-ozone combination) potentially increased the virulence of Salmonella, as evidenced by heightened inflammatory responses in the colon, despite achieving similar colonization rates by day five. This suggests that sublethal egg processing can exasperate the risk of Salmonella transmission, since it may enhance pathogen virulence, posing significant safety risks to consumers. These findings underscore the need for careful optimization of egg pasteurization methods to alleviate the potential for increased Salmonella pathogenicity.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2023
Citation:
Abdelhamid AG and Yousef AE (2023). Egg-associated Salmonella enterica serovar Enteritidis: comparative genomics unveils phylogenetic links, virulence potential, and antimicrobial resistance traits. Front. Microbiol. 14:1278821.doi: 10.3389/fmicb.2023.1278821
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Progress 05/01/22 to 04/30/23
Outputs
Target Audience:- The community of the International Assocaition of Food Protection - Members of the Institute of Food Technologists - The egg industry, represented by the Ohio Poultry Assocaition Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Working on this this project, graduate student, Yumin Xu, obtained her Ph. D. degree at The Ohio State University. Immediately after graduation, she was employed by Abbott as a research scientist. The project was an opportunity to train post-doctorate, Ahmed G. Abdelhamid, on the use of animal model in food safety research. How have the results been disseminated to communities of interest?Publication of the paper, listed earlier, was a great way to disseminate project results. As of today, the article was downloaded224 times (https://journals.asm.org/doi/10.1128/aem.01140-22). What do you plan to do during the next reporting period to accomplish the goals?We were granted project extension for one year to allow us complete Goal 2 research. This will give usa chance to study the changes in Salmonella virulence when contaminated eggs are administered to streptomycin-treated mice.
Impacts
What was accomplished under these goals?
Research Impact: Pasteurization of shell eggs is an important technology designed to protect consumers against Salmonella Enteritidis that contaminates this commodity. Slow heating rate is preferred over fast rate during shell egg thermal pasteurization due to product quality concern. However, it is not known whether raising the temperature at different rates, during pasteurizing, would potentially affect product safety determinants. The current study demonstrated that slow heating during pasteurization come-up stage increased these risks: (1) resistance of Salmonella to pasteurization holding stage or to subsequent ozone treatment, (2) recovery of Salmonella during the cooling that followed pasteurization, and (3) Salmonella's ability to causes disease (i.e., virulence). Our findings inform food processors about potential safety risks to consumers resulting from improper use of processing parameters during shell egg pasteurization. Additionally, treating shell eggs with ozone after heat treatment could alleviate these hazards and protect consumers from natural Salmonella Enteritidis contaminants in shell eggs. The third goal of the study "Determining the heat resistance, measured as D-value, ofSalmonellaEnteritidis grown in shell eggs and treated with heat and ozone" was fully addressed during this reporting period. This phase of the study covered experiments todetermine if shell eggs heating rate, which varies with different pasteurization implementations, alters Salmonella Enteritidis response to different stresses or expression of virulence. Shell eggs, containing Salmonella Enteritidis in yolk, were subjected to slow (2.4°C /min) or fast (3.5 °C/min) heating rate during treatments that mimicked pasteurization temperature come-up stage. Slow heating rate protected Salmonella from these processes: (a) lethal heat at the holding stage, (b) loss of viability during 8-h cooling past heating, and (c) sequential antimicrobial ozone treatment. Transcriptional analysis revealed that the heat stress response gene, grpE, was transcribed 3-fold higher during the slow, compared to the fast-heating rate. Slow heating also significantly increased the expression of selected Salmonella virulence-related genes, sopB and sseA, in newly constructed reporter strains. Salmonella virulence was determined experimentally as LD50 values in an in vivo model. The slow heat treatment mildly increased Salmonella Enteritidis virulence in mice (LD50 of 3.3 log CFU), compared to that in non-treated yolk (LD50 of 3.9 log CFU). However, when ozone application followed the slow heat treatment, Salmonella virulence decreased (LD50 of 4.2 log CFU), compared to that for heat treated or non-treated yolk. In conclusion, heating shell eggs at slow rate can trigger a series of hazardous responses that may compromise the safety of the final pasteurized products but following the thermal treatment with ozone application may help alleviating these concerns. In conclusion,potential safety risks associated with slow heating of Salmonella-contaminated shell eggs was investigated in the current study. Slow heating rate at the pasteurization come-up stage, which was achieved by raising egg internal temperature from ambient to 50°C in ~20 minutes, triggered profound heat stress response in Salmonella Enteritidis, in comparison to faster heating rates, which was attained by raising egg internal temperature from ambient to 50°C in ~10 minutes. This stress response during the heating come-up stage not only increased the pathogen's resistance to an ensuing thermal processing, but it also protected the pathogen against a subsequent ozone treatment. Even if the holding temperature was high, Salmonella pre-exposed to slow heating rate showed more protection against the remaining heat during egg cooling stage. Moreover, slowing heating rate prompted the expression of Salmonella virulence genes and resulted in higher death rate and faster onset of disease in a mouse model. Therefore, it is suggested that low temperature, long time, treatment is not equivalent in product safety to the high temperature, short time, treatment, even if both are set to achieve the same log reduction of the targeted pathogen. However, when the heat treatment was followed with application of ozone, the pathogen's virulence in the mouse model was reduced.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2022
Citation:
Xu Y, Abdelhamid AG, Sabag-Daigle A, Ahmer BMM, Yousef AE. 2022. Heating rate during shell egg thermal treatment elicits stress responses and alters virulence of Salmonella enterica serovar Enteritidis; implications for shell egg pasteurization. Appl Environ Microbiol 88:e0114022. https://doi.org/10.1128/aem.01140-22
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Progress 05/01/21 to 04/30/22
Outputs
Target Audience:Farmers aiming to implement egg production using cage-free hens (Salmonella contamination is expected to increase) and FDA Changes/Problems:Because objective 2 required a very large number of mice to study, part of this objective will be completed during the third year (instead of the second year) of the project. What opportunities for training and professional development has the project provided?Post-Doc trainee, Dr. Ahmed G. Abdelhamid: This trainee had a chance to work cooperatively with a graduate student on this project. Both gained experience in publishing the results of their study. Ph.D. candidate, Yumin Xu: The project became her main dissertation subject. Recently, she completed her work and graduated earning a Ph.D. degree of food science. Dr. Xu was hired immediately after graduation by a major food company. How have the results been disseminated to communities of interest?Results of the study were shared at the following academic and public meetings: The Ohio State University 36th Annual Edward F. Hayes Graduate Research Forum, March 4, 2022. The research was presented by graduate student, Yumin Xu, who won the first place in that competition {https://fst.osu.edu/news/food-science-students-represent-hayes-research-forum} Graduate seminar (Autumn, 2021), Department of Food Science and Technology, The Ohio State University Ph.D. exit seminar (Spring, 2022), Department of Food Science and Technology, The Ohio State University. What do you plan to do during the next reporting period to accomplish the goals?Complete the remaining sub-objectives: Effect of different sublethal heating rates of shell eggs on the resistance of Salmonella Enteritidis(in yolk)to subsequent lethal heat and ozone treatments. Assessing the virulence expression in mouse model when infected with Salmonella Enteritidis in shell eggs that were treated with heat, ozone and heat-ozone combination.
Impacts
What was accomplished under these goals?
Goal 2: Assessing the virulence expression in mouse model when infected with Salmonella Enteritidis grown in shell eggs. Contribution of food vehicles to pathogenicity of disease-causing microorganisms is an important but overlooked research field. The current study was initiated to reveal the relationship between virulence of Salmonella enterica serovar Enteritidis and egg yolk as a hosting medium. Mice were orally challenged with Salmonella Enteritidis cultured in egg yolk or tryptic soy broth (TSB). Additionally, mice were challenged with Salmonella Enteritidis cultured in TSB, followed by administration of sterile egg yolk, to discern the difference between pre-growth of the pathogen and its mere presence in egg yolk during infection. The pathogen's Lethal dose 50 (LD50) was the lowest when grown in yolk (2.8×102 CFU), compared to 1.1×103 CFU in TSB, and 4.6×103 CFU in TSB followed by administration of sterile yolk. Additionally, mice orally received Salmonella Enteritidis grown in egg yolk expressed high death rate. These findings were supported by transcriptional analysis results. Expression of promoters of virulence-related genes (sopB and sseA) in genetically modified Salmonella Enteritidis reporter strains, was significantly higher (p < 0.05) when the bacterium was grown in the yolk, compared to that grown in TSB. Sequencing of RNA (RNA-seq) revealed 204 differentially transcribed genes in Salmonella Enteritidis grown in yolk vs. TSB. Yolk-grown Salmonella Enteritidis exhibited upregulated virulence pathways, including type III secretion systems, epithelial cell invasion, and infection processes; these observations were confirmed by RT-qPCR results. The transcriptomic analysis suggested that upregulation of virulence machinery of Salmonella Enteritidis grown in egg yolk was related to increased iron-uptake, biotin utilization, flagellar biosynthesis, and export of virulence proteins encoded on Salmonella pathogenicity island 1, 2, 4, and 5. These biological responses may have acted in concert to increase the virulence of Salmonella infection in mice. In conclusion, growth in egg yolk enhanced Salmonella Enteritidis virulence, indicating the significance of this food vehicle to the risk assessment of salmonellosis.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2022
Citation:
Xu Y, Abdelhamid AG, Sabag-Daigle A, Sovic MG, Ahmer BMM, Yousef AE. 2022. The role of egg yolk in modulating the virulence of Salmonella enterica serovar Enteritidis. Front Cell Infect Microbiol 12:903979. https://doi.org/10.3389/fcimb.2022.903979
- Type:
Theses/Dissertations
Status:
Published
Year Published:
2022
Citation:
Xu, Y. 2022. Increased virulence and processing resistance of Salmonella Enteritidis in the egg environment: Understanding the paradigm of food as a vehicle for human infection. (Ph.D. dissertation). The Ohio State University, Columbus, Ohio.
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Progress 05/01/20 to 04/30/21
Outputs
Target Audience:The audience of the International Association of Food Protection (IAFP) The egg industry, represented by the Ohio Poultry Association. Changes/Problems:We encountered technical problems in extracting mRNA from Salmonella present in egg yolk. We developed an alternative procedure to determine the levels of genes expression that is not dependant on mRNA extraction. The newly developed procedure eventually succeeded, but resulted in delays. Therefore, we accomplished most of objective one, which we initially intended to complete totally during the first year. What opportunities for training and professional development has the project provided?Training a Ph.D. graduate student (Yumin Xu): The project became her main dissertation subject. Draining Post-Doc (Ahmed G. Abdelhamid): He had a chance to practicemoecular biology skills at the heighest level. How have the results been disseminated to communities of interest?Y. Xu, A.G. Abdelhamid, A. Sabag-Daigle, B.M. Ahmer and A.E. Yousef. 2021. Pathogens turn hypervirulent during colonization of food: Salmonella Enteritidis in egg as an example. Presentation at the annual meeting of the International Association of Food Protection, Phoenix, Arizona. What do you plan to do during the next reporting period to accomplish the goals?Future experiments: The impact of different ozone concentrations (4%-10%) on virulence genes of Salmonella Enteritidis grown in shell eggs will be determined. This was part of goal 1 but it is was completed during the first year due to the methodological problems that we faced and needed to address them before proceeding. Verifying the virulence expression in mouse model when infected with Salmonella Enteritidis grown in shell eggs and treated with heat, ozone and heat-ozone combination.
Impacts
What was accomplished under these goals?
Goal 1: Determining the changes in the transcription of genes encoding (a) general and specific stress regulators and (b) virulence, when Salmonella Enteritidis is grown in shell eggs and exposed to different heating rates. This report coveres the progress on exploring how different heating rates affect the transcription of genes encoding general and specific stress regulators and virulence, when Salmonella Enteritidis is grown in shell eggs. Initially, RT-qPCR was used for detecting the expression of heat stress-related genes (rpoH, clpB, grpE and htrA) and virulence genes (hilC, sipA and pipB) at both slow and fast heating rates. Although promising trends were observed, there were no significant differences among treatments due to the high variability, as evident from high standard deviations. An alternative method, which used luciferase reporter system, was applied for a more accurate and spontaneous measurement of the gene expression. To acheive that, reporter strains were generated to screen for heat stress related genes (grpE::luxCDABE) and virulence genes (sopB::luxCDABE and sseA::luxCDABE). Results suggested that heat induced upregulation of both heat stress-related genes and virulence genes, and the slower the heating rate, the stronger the expression of those genes. The following are the completed experiments: 1. The transcriptional changes in heat stress response and virulence genes using the RT-qPCR approach a. RT-qPCR results of heat stress response related genes. During heating come-up stage, the gene expression level of rpoH was 4.6±4.3 and 7.7±2.7 fold for fast heating rate when the egg internal temperature was 42 and 47 °C, respectively; 4.2 and 4.3±2.2 fold for slow heating rate. The gene expression level of clpB was 2.0 and 3.5±0.5 fold for fast heating rate when the egg internal temperature was 42 and 47 °C, respectively; 5.3 and 4.7± 1.7 fold for slow heating rate. The gene expression level of grpE was 11.9±8.2 and 7.6±4.1 fold at 42 and 47 °C, respectively, for fast heating rate and 4.9 and 37.3±45.4 fold for slow heating rate. The expression level of htrA was 2.6±4.4 and 0.6±3.6 fold at 42 and 47 °C, respectively, for fast heating rate and 1.1 and 4.7±4.6 fold for slow heating. After the eggs were removed from heating water bath and let cool at 30 °C for 15 min, the gene expression levels of rpoH, clpB, grpE and htrA for fast heating rate were 1.2, -6.3, 2.8 and -2.5, respectively, and 3.6±0.8, 5.0±3.3, 14.1±9.7 and 7.0±11.4 for slow heating rate. Two-way ANOVA suggested that neither the egg internal temperature nor the different heating rate was a significant factor to influence the expression level of any of the gene tested. This can be attributed to the high standard deviations among the compared genes. b. RT-qPCR results of virulence genes. During temperature come-up stage, the gene expression level of hilC was 0.7±3.2 and 3.5±5.1 fold for fast heating rate when the egg internal temperature was 42 and 47 °C, respectively; -0.13±2.3 and -1.1±3.4 fold for slow heating rate. The gene expression level of sipA was -0.4±2.5 and 1.5±2.9 fold for fast heating rate when the egg internal temperature was 42 and 47 °C, respectively; -4.2±1.7 and -1.2±7.5 fold for slow heating rate. The gene expression level of pipB was 2.7±5.7 and 10.2±10.9 fold at 42 and 47 °C, respectively, for fast heating rate and 0.1±2.1 and 2.5±2.2 fold for slow heating rate. After the eggs were removed from water bath and cooled at 30 °C for 15 min, the gene expression level of hilC, sipA, and pipB for fast heating rate was 15.1±7.0, -1.7±1.1, and 14.3, respectively, and -2.2±4.0, -0.8±4.4, and 4.8±1.7 for slow heating rate. Two-way ANOVA indicated that neither factors (the egg internal temperature not the heating rate) was significantly affecting the expression level of any of the targeted genes. 2. The transcriptional changes in heat stress response and virulence genes using the plasmid reporter system approach To overcome the transcriptional measurements irregularities, which were observed as large standard deviations, when using the RT-qPCR approach, we adopted the plasmid reporter system for consistent and robust experimental measurement of the expression of target genes. a. Recovery of luciferase activity. The gene, 16s rRNA, was chosen for calculating the luciferase activity because it is a housekeeping gene whose expression should not change in response to heat and thus, the increasein luminescence was expected to be only due to the recovery of the luciferase activity. The recovery of luciferase activity after the samples being incubated at 37°C for 45 min varied according to the heating rates. When eggs were submerged in water bath held at 53, 55, 57 and 59 °C, this represented the slowest heating rate to the fastest heating rate during the come-up stage and the recovery rates of luciferase activity were 33.2±5.4, 22.5±3.7, 17.1±9.8 and 14.5±3.0%, respectively. The recovery rate at the slowest (53 °C) was significantly higher than that of the fastest heating rate (59 °C) (p = 0.04). b. Expression of heat stress response-related genes at various heating rates using reporter system. The normalized luminescence of grpE promoter after 45-min recovery was 5643.1±505.2, 4663±388.2, 3782.4±1232.5 and 1898.0±408.0 luminescence/ log (CFU/ml), respectively, from the slowest heating rate to the fastest heating rate. In comparison to the expression of grpE of Salmonella without heat treatment which the normalized luminescence was 1069.3±30.6 luminescence/ log (CFU/ml), heat treatment resulted in a significant upregulation of heat stress-related gene regardless the heating rate. However, the slower the heating rate, the more profound the expression of grpE; the expression of grpE was significantly lower at the fastest heating rate (59 °C) than those of the slower heating rates, 53 °C (p = 0.001) and 55? (p = 0.007). c. Expression of virulence genes at various heating rates using reporter system. When eggs were heated in water bath at 53, 55, 57 and 59 °C, the normalized luminescence of sopB promoter was 9713.5±124.7, 8318.4±1526.3, 6554.5±580.0 and 5406.6±950.6 luminescence/ log (CFU/ml), respectively, while the normalized luminescence of sseA promoter was 7637.6±1403.0, 7168.4±588.3, 2870.0±1116.8 and 2749.0±650.4 luminescence/ log (CFU/ml). The slower heating rates (53 °C and 55 °C) led to significantly higher expression of virulence genes in comparison to the controls, except that for sopB, 55 °C was not significantly different from 57 °C. Heating caused significant upregulation of both sopB and sseA when compared to the controls which were 1277.5±396.3 and 1752.6±294.0 luminescence/ log (CFU/ml), respectively. Accomplishments: A study addressing the impact of different heating rates on the expression of heat stress response genes and virulence genes of Salmonella Enteritidis grown in shell eggs was completed successfully. Luminescence-based reporter systems were successfully constructed; this allowed for determining the transcriptional changes of heat stress response and virulence gens inSalmonellaEnteritidis. The method's measurements were instantaneous, robust, and accurate.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2021
Citation:
Xu Y, Abdelhamid AG, Yousef AE. 2021. Draft genome sequence of Salmonella enterica subsp. enterica serovar Enteritidis ODA 99-30581-13, a heat-resistant strain isolated from shell eggs. Microbiol Resour Announc 10:e01461-20.
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