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Gast RK, Dittoe DK, Ricke SC. Salmonella in eggs and egg-laying chickens: pathways to effective control. Crit Rev Microbiol 2024; 50:39-63. [PMID: 36583653 DOI: 10.1080/1040841x.2022.2156772] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2022] [Accepted: 12/05/2022] [Indexed: 12/31/2022]
Abstract
Eggs contaminated with Salmonella have been internationally significant sources of human illness for several decades. Most egg-associated illness has been attributed to Salmonella serovar Enteritidis, but a few other serovars (notably S. Heidelberg and S. Typhimurium) are also sometimes implicated. The edible interior contents of eggs typically become contaminated with S. Enteritidis because the pathogen's unique virulence attributes enable it to colonize reproductive tissues in systemically infected laying hens. Other serovars are more commonly associated with surface contamination of eggshells. Both research and field experience have demonstrated that the most effective overall Salmonella control strategy in commercial laying flocks is the application of multiple interventions throughout the egg production cycle. At the preharvest (egg production) level, intervention options of demonstrated efficacy include vaccination and gastrointestinal colonization control via treatments such as prebiotics, probiotics, and bacteriophages, Effective environmental management of housing systems used for commercial laying flocks is also essential for minimizing opportunities for the introduction, transmission, and persistence of Salmonella in laying flocks. At the postharvest (egg processing and handling) level, careful regulation of egg storage temperatures is critical for limiting Salmonella multiplication inside the interior contents.
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Affiliation(s)
- Richard K Gast
- U.S. National Poultry Research Center, USDA Agricultural Research Service, Athens, GA, USA
| | - Dana K Dittoe
- Department of Animal and Dairy Sciences, Meat Science and Animal Biologics Discovery Program, University of Wisconsin, Madison, WI, USA
| | - Steven C Ricke
- Department of Animal and Dairy Sciences, Meat Science and Animal Biologics Discovery Program, University of Wisconsin, Madison, WI, USA
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2
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Hoppe-Elsholz G, Piña-Iturbe A, Vallejos OP, Suazo ID, Sepúlveda-Alfaro J, Pereira-Sánchez P, Martínez-Balboa Y, Catalán EA, Reyes P, Scaff V, Bassi F, Campos-Gajardo S, Avilés A, Santiviago CA, Kalergis AM, Bueno SM. SEN1990 is a predicted winged helix-turn-helix protein involved in the pathogenicity of Salmonella enterica serovar Enteritidis and the expression of the gene oafB in the SPI-17. Front Microbiol 2023; 14:1236458. [PMID: 38029095 PMCID: PMC10655114 DOI: 10.3389/fmicb.2023.1236458] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Accepted: 09/27/2023] [Indexed: 12/01/2023] Open
Abstract
Excisable genomic islands (EGIs) are horizontally acquired genetic elements that harbor an array of genes with diverse functions. ROD21 is an EGI found integrated in the chromosome of Salmonella enterica serovar Enteritidis (Salmonella ser. Enteritidis). While this island is known to be involved in the capacity of Salmonella ser. Enteritidis to cross the epithelial barrier and colonize sterile organs, the role of most ROD21 genes remains unknown, and thus, the identification of their function is fundamental to understanding the impact of this EGI on bacterium pathogenicity. Therefore, in this study, we used a bioinformatical approach to evaluate the function of ROD21-encoded genes and delve into the characterization of SEN1990, a gene encoding a putative DNA-binding protein. We characterized the predicted structure of SEN1990, finding that this protein contains a three-stranded winged helix-turn-helix (wHTH) DNA-binding domain. Additionally, we identified homologs of SEN1990 among other members of the EARL EGIs. Furthermore, we deleted SEN1990 in Salmonella ser. Enteritidis, finding no differences in the replication or maintenance of the excised ROD21, contrary to what the previous Refseq annotation of the protein suggests. High-throughput RNA sequencing was carried out to evaluate the effect of the absence of SEN1990 on the bacterium's global transcription. We found a downregulated expression of oafB, an SPI-17-encoded acetyltransferase involved in O-antigen modification, which was restored when the deletion mutant was complemented ectopically. Additionally, we found that strains lacking SEN1990 had a reduced capacity to colonize sterile organs in mice. Our findings suggest that SEN1990 encodes a wHTH domain-containing protein that modulates the transcription of oafB from the SPI-17, implying a crosstalk between these pathogenicity islands and a possible new role of ROD21 in the pathogenesis of Salmonella ser. Enteritidis.
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Affiliation(s)
- Guillermo Hoppe-Elsholz
- Millennium Institute on Immunology and Immunotherapy, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Alejandro Piña-Iturbe
- Millennium Institute on Immunology and Immunotherapy, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Omar P. Vallejos
- Millennium Institute on Immunology and Immunotherapy, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Isidora D. Suazo
- Millennium Institute on Immunology and Immunotherapy, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Javiera Sepúlveda-Alfaro
- Millennium Institute on Immunology and Immunotherapy, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Patricia Pereira-Sánchez
- Millennium Institute on Immunology and Immunotherapy, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Yohana Martínez-Balboa
- Millennium Institute on Immunology and Immunotherapy, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Eduardo A. Catalán
- Millennium Institute on Immunology and Immunotherapy, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Pablo Reyes
- Millennium Institute on Immunology and Immunotherapy, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Valentina Scaff
- Millennium Institute on Immunology and Immunotherapy, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Franco Bassi
- Millennium Institute on Immunology and Immunotherapy, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Sofia Campos-Gajardo
- Millennium Institute on Immunology and Immunotherapy, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Andrea Avilés
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Santiago, Chile
| | - Carlos A. Santiviago
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Santiago, Chile
| | - Alexis M. Kalergis
- Millennium Institute on Immunology and Immunotherapy, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
- Departamento de Endocrinología, Facultad de Medicina, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Susan M. Bueno
- Millennium Institute on Immunology and Immunotherapy, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
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3
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Wang S, Xiao X, Qiu M, Wang W, Xiao Y, Yang H, Dang Y, Wang W. Transcriptomic Responses of Salmonella enterica Serovars Enteritidis in Sodium Hypochlorite. Front Cell Infect Microbiol 2022; 12:853064. [PMID: 35521218 PMCID: PMC9065344 DOI: 10.3389/fcimb.2022.853064] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2022] [Accepted: 03/24/2022] [Indexed: 11/24/2022] Open
Abstract
Salmonella enterica serovars Enteritidis (S. Enteritidis) can survive extreme food processing environments including bactericidal sodium hypochlorite (NaClO) treatments generally recognized as safe. In order to reveal the molecular regulatory mechanisms underlying the phenotypes, the overall regulation of genes at the transcription level in S. Enteritidis after NaClO stimulation were investigated by RNA-sequencing. We identified 1399 differentially expressed genes (DEG) of S. Enteritidis strain CVCC 1806 following treatment in liquid culture with 100 mg/L NaClO for 20 min (915 upregulated and 484 downregulated). NaClO stress affects the transcription of genes related to a range of important biomolecular processes such as membrane damage, membrane transport function, energy metabolism, oxidative stress, DNA repair, and other important processes in Salmonella enterica. First, NaClO affects the structural stability of cell membranes, which induces the expression of a range of outer and inner membrane proteins. This may lead to changes in cell membrane permeability, accelerating the frequency of DNA conversion and contributing to the production of drug-resistant bacteria. In addition, the expression of exocytosis pump genes (emrB, yceE, ydhE, and ydhC) was able to expel NaClO from the cell, thereby increasing bacterial tolerance to NaClO. Secondly, downregulation of genes related to the Kdp-ATPase transporter system (kdpABC) and the amino acid transporter system (aroP, brnQ and livF) may to some extent reduce active transport by bacterial cells, thereby reducing their own metabolism and the entry of disinfectants. Downregulation of genes related to the tricarboxylic acid (TCA) cycle may drive bacterial cells into a viable but non-culturable (VBNC) state, resisting NaClO attack by reducing energy metabolism. In addition, significant upregulation of genes related to oxidative stress could mitigate damage caused by disinfectants by eliminating alkyl hydroperoxides, while upregulation of genes related to DNA repair could repair damage to bacterial cells caused by oxidative stress. Therefore, this study indicated that S. Enteritidis has genomic mechanisms to adapt to NaClO stress.
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Affiliation(s)
- Sheng Wang
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-Products, College of Food and Pharmaceutical Sciences, Ningbo University, Ningbo, China
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-Products, MOA Laboratory of Quality & Safety Risk Assessment for Agro-Products (Hangzhou), Institute of Agro-Product Safety and Nutrition, Zhejiang Academy of Agricultural Sciences, Hangzhou, China
| | - Xingning Xiao
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-Products, MOA Laboratory of Quality & Safety Risk Assessment for Agro-Products (Hangzhou), Institute of Agro-Product Safety and Nutrition, Zhejiang Academy of Agricultural Sciences, Hangzhou, China
| | - Mengjia Qiu
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-Products, MOA Laboratory of Quality & Safety Risk Assessment for Agro-Products (Hangzhou), Institute of Agro-Product Safety and Nutrition, Zhejiang Academy of Agricultural Sciences, Hangzhou, China
- School of Health Science and Engineering, University of Shanghai for Science and Technology, Shanghai, China
| | - Wensi Wang
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-Products, MOA Laboratory of Quality & Safety Risk Assessment for Agro-Products (Hangzhou), Institute of Agro-Product Safety and Nutrition, Zhejiang Academy of Agricultural Sciences, Hangzhou, China
- College of Food Science and Engineering, Wuhan Polytechnic University, Wuhan, China
| | - Yingping Xiao
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-Products, MOA Laboratory of Quality & Safety Risk Assessment for Agro-Products (Hangzhou), Institute of Agro-Product Safety and Nutrition, Zhejiang Academy of Agricultural Sciences, Hangzhou, China
| | - Hua Yang
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-Products, MOA Laboratory of Quality & Safety Risk Assessment for Agro-Products (Hangzhou), Institute of Agro-Product Safety and Nutrition, Zhejiang Academy of Agricultural Sciences, Hangzhou, China
| | - Yali Dang
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-Products, College of Food and Pharmaceutical Sciences, Ningbo University, Ningbo, China
- *Correspondence: Wen Wang, ; Yali Dang,
| | - Wen Wang
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-Products, MOA Laboratory of Quality & Safety Risk Assessment for Agro-Products (Hangzhou), Institute of Agro-Product Safety and Nutrition, Zhejiang Academy of Agricultural Sciences, Hangzhou, China
- *Correspondence: Wen Wang, ; Yali Dang,
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Advancement in Salmonella Detection Methods: From Conventional to Electrochemical-Based Sensing Detection. BIOSENSORS-BASEL 2021; 11:bios11090346. [PMID: 34562936 PMCID: PMC8468554 DOI: 10.3390/bios11090346] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Revised: 09/06/2021] [Accepted: 09/09/2021] [Indexed: 02/07/2023]
Abstract
Large-scale food-borne outbreaks caused by Salmonella are rarely seen nowadays, thanks to the advanced nature of the medical system. However, small, localised outbreaks in certain regions still exist and could possess a huge threat to the public health if eradication measure is not initiated. This review discusses the progress of Salmonella detection approaches covering their basic principles, characteristics, applications, and performances. Conventional Salmonella detection is usually performed using a culture-based method, which is time-consuming, labour intensive, and unsuitable for on-site testing and high-throughput analysis. To date, there are many detection methods with a unique detection system available for Salmonella detection utilising immunological-based techniques, molecular-based techniques, mass spectrometry, spectroscopy, optical phenotyping, and biosensor methods. The electrochemical biosensor has growing interest in Salmonella detection mainly due to its excellent sensitivity, rapidity, and portability. The use of a highly specific bioreceptor, such as aptamers, and the application of nanomaterials are contributing factors to these excellent characteristics. Furthermore, insight on the types of biorecognition elements, the principles of electrochemical transduction elements, and the miniaturisation potential of electrochemical biosensors are discussed.
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Gast RK, Jones DR, Guraya R, Anderson KE, Karcher DM. Research Note: Contamination of eggs by Salmonella Enteritidis and Salmonella Typhimurium in experimentally infected laying hens in indoor cage-free housing. Poult Sci 2021; 100:101438. [PMID: 34525442 PMCID: PMC8445890 DOI: 10.1016/j.psj.2021.101438] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Accepted: 08/15/2021] [Indexed: 11/25/2022] Open
Abstract
Contaminated eggs are a leading source of human Salmonella infections and this problem continues to challenge public health authorities and egg industries around the world. Salmonella invasion of the ovaries and oviducts of infected laying hens can result in bacterial deposition inside the edible portions of developing eggs. The introduction, persistence, and transmission of salmonellae in commercial egg-laying flocks are influenced by flock management practices, but the food safety ramifications of different types of laying hen housing remain unresolved. The present study assessed the frequency of internal contamination of eggs after experimental Salmonella Enteritidis and S. Typhimurium infection of laying hens in indoor cage-free housing. Groups of 72 hens were housed on wood shavings in isolation rooms simulating commercial cage-free barns with community kick-out nest boxes and perches and 1/3 of the hens in each room were orally inoculated with 8.0 × 107 cfu of 2-strain mixtures of either S. Enteritidis (2 rooms) or S. Typhimurium (2 rooms), and the entire internal contents of all eggs laid 5 to 30 d postinoculation in nest boxes or on the flooring substrate were cultured to detect Salmonella. Contaminated eggs were laid between 8 and 28 d postinoculation. The overall incidence of S. Enteritidis isolation from eggs (3.41%) was significantly (P = 0.0005) greater than S. Typhimurium (1.19%). The contamination frequencies associated with the 2 egg collection locations were not significantly different (P > 0.05). These results demonstrate that oral infection of a relatively small proportion of laying hens in indoor cage-free housing with invasive Salmonella serovars can result in the production of internally contaminated eggs at low frequencies over a period of nearly a month postinoculation.
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Affiliation(s)
- Richard K Gast
- U. S. National Poultry Research Center, USDA Agricultural Research Service, Athens, GA 30605, USA.
| | - Deana R Jones
- U. S. National Poultry Research Center, USDA Agricultural Research Service, Athens, GA 30605, USA
| | - Rupa Guraya
- U. S. National Poultry Research Center, USDA Agricultural Research Service, Athens, GA 30605, USA
| | - Kenneth E Anderson
- Department of Poultry Science, North Carolina State University, Raleigh, NC 29765, USA
| | - Darrin M Karcher
- Department of Animal Sciences, Purdue University, West Lafayette, IN 47907, USA
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6
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Zhou X, Liu B, Liu Y, Shi C, Fratamico PM, Zhang L, Wang D, Zhang J, Cui Y, Xu P, Shi X. Two homologous Salmonella serogroup C1-specific genes are required for flagellar motility and cell invasion. BMC Genomics 2021; 22:507. [PMID: 34225670 PMCID: PMC8259012 DOI: 10.1186/s12864-021-07759-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Accepted: 05/26/2021] [Indexed: 11/16/2022] Open
Abstract
Background Salmonella is a major bacterial pathogen associated with a large number of outbreaks of foodborne diseases. Many highly virulent serovars that cause human illness belong to Salmonella serogroup C1, and Salmonella ser. Choleraesuis is a prominent cause of invasive infections in Asia. Comparative genomic analysis in our previous study showed that two homologous genes, SC0368 and SC0595 in Salmonella ser. Choleraesuis were unique to serogroup C1. In this study, two single-deletion mutants (Δ0368 and Δ0595) and one double-deletion mutant (Δ0368Δ0595) were constructed based on the genome. All these mutants and the wild-type strain were subjected to RNA-Seq analysis to reveal functional relationships of the two serogroup C1-specific genes. Results Data from RNA-Seq indicated that deletion of SC0368 resulted in defects in motility through repression of σ28 in flagellar regulation Class 3. Consistent with RNA-Seq data, results from transmission electron microcopy (TEM) showed that flagella were not present in △0368 and △0368△0595 mutants resulting in both swimming and swarming defects. Interestingly, the growth rates of two non-motile mutants △0368 and △0368△0595 were significantly greater than the wild-type, which may be associated with up-regulation of genes encoding cytochromes, enhancing bacterial proliferation. Moreover, the △0595 mutant was significantly more invasive in Caco-2 cells as shown by bacterial enumeration assays, and the expression of lipopolysaccharide (LPS) core synthesis-related genes (rfaB, rfaI, rfaQ, rfaY, rfaK, rfaZ) was down-regulated only in the △0368△0595 mutant. In addition, this study also speculated that these two genes might be contributing to serotype conversion for Salmonella C1 serogroup based on their apparent roles in biosynthesis of LPS and the flagella. Conclusion A combination of biological and transcriptomic (RNA-Seq) analyses has shown that the SC0368 and SC0595 genes are involved in biosynthesis of flagella and complete LPS, as well as in bacterial growth and virulence. Such information will aid to revealing the role of these specific genes in bacterial physiology and evolution within the serogroup C1. Supplementary Information The online version contains supplementary material available at 10.1186/s12864-021-07759-z.
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Affiliation(s)
- Xiujuan Zhou
- MOST-USDA Joint Research Center for Food Safety, School of Agriculture & Biology, and State Key Lab of Microbial Metabolism, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Bin Liu
- College of Food Science and Engineering, Northwest Agriculture and Forestry University, Yangling, 712100, Shaanxi, China
| | - Yanhong Liu
- Molecular Characterization of Foodborne Pathogens Research Unit, Eastern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, 600 East Mermaid Lane, Wyndmoor, PA, 19038, USA
| | - Chunlei Shi
- MOST-USDA Joint Research Center for Food Safety, School of Agriculture & Biology, and State Key Lab of Microbial Metabolism, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Pina M Fratamico
- Molecular Characterization of Foodborne Pathogens Research Unit, Eastern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, 600 East Mermaid Lane, Wyndmoor, PA, 19038, USA
| | - Lida Zhang
- MOST-USDA Joint Research Center for Food Safety, School of Agriculture & Biology, and State Key Lab of Microbial Metabolism, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Dapeng Wang
- MOST-USDA Joint Research Center for Food Safety, School of Agriculture & Biology, and State Key Lab of Microbial Metabolism, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Jianhua Zhang
- MOST-USDA Joint Research Center for Food Safety, School of Agriculture & Biology, and State Key Lab of Microbial Metabolism, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Yan Cui
- MOST-USDA Joint Research Center for Food Safety, School of Agriculture & Biology, and State Key Lab of Microbial Metabolism, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Ping Xu
- MOST-USDA Joint Research Center for Food Safety, School of Agriculture & Biology, and State Key Lab of Microbial Metabolism, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Xianming Shi
- MOST-USDA Joint Research Center for Food Safety, School of Agriculture & Biology, and State Key Lab of Microbial Metabolism, Shanghai Jiao Tong University, Shanghai, 200240, China.
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Legros J, Jan S, Bonnassie S, Gautier M, Croguennec T, Pezennec S, Cochet MF, Nau F, Andrews SC, Baron F. The Role of Ovotransferrin in Egg-White Antimicrobial Activity: A Review. Foods 2021; 10:823. [PMID: 33920211 PMCID: PMC8070150 DOI: 10.3390/foods10040823] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Revised: 04/07/2021] [Accepted: 04/08/2021] [Indexed: 12/17/2022] Open
Abstract
Eggs are a whole food which affordably support human nutritional requirements worldwide. Eggs strongly resist bacterial infection due to an arsenal of defensive systems, many of which reside in the egg white. However, despite improved control of egg production and distribution, eggs remain a vehicle for foodborne transmission of Salmonella enterica serovar Enteritidis, which continues to represent a major public health challenge. It is generally accepted that iron deficiency, mediated by the iron-chelating properties of the egg-white protein ovotransferrin, has a key role in inhibiting infection of eggs by Salmonella. Ovotransferrin has an additional antibacterial activity beyond iron-chelation, which appears to depend on direct interaction with the bacterial cell surface, resulting in membrane perturbation. Current understanding of the antibacterial role of ovotransferrin is limited by a failure to fully consider its activity within the natural context of the egg white, where a series relevant environmental factors (such as alkalinity, high viscosity, ionic composition, and egg white protein interactions) may exert significant influence on ovotransferrin activity. This review provides an overview of what is known and what remains to be determined regarding the antimicrobial activity of ovotransferrin in egg white, and thus enhances understanding of egg safety through improved insight of this key antimicrobial component of eggs.
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Affiliation(s)
- Julie Legros
- STLO, INRAE, Institut Agro, 35042 Rennes, France; (J.L.); (S.J.); (M.G.); (T.C.); (S.P.); (M.-F.C.); (F.N.)
- School of Biological Sciences, Health and Life Sciences Building, University of Reading, Reading RG6 6AX, UK;
| | - Sophie Jan
- STLO, INRAE, Institut Agro, 35042 Rennes, France; (J.L.); (S.J.); (M.G.); (T.C.); (S.P.); (M.-F.C.); (F.N.)
| | - Sylvie Bonnassie
- UFR Sciences de la vie et de L’environnement, Université de Rennes 1, 35000 Rennes, France;
| | - Michel Gautier
- STLO, INRAE, Institut Agro, 35042 Rennes, France; (J.L.); (S.J.); (M.G.); (T.C.); (S.P.); (M.-F.C.); (F.N.)
| | - Thomas Croguennec
- STLO, INRAE, Institut Agro, 35042 Rennes, France; (J.L.); (S.J.); (M.G.); (T.C.); (S.P.); (M.-F.C.); (F.N.)
| | - Stéphane Pezennec
- STLO, INRAE, Institut Agro, 35042 Rennes, France; (J.L.); (S.J.); (M.G.); (T.C.); (S.P.); (M.-F.C.); (F.N.)
| | - Marie-Françoise Cochet
- STLO, INRAE, Institut Agro, 35042 Rennes, France; (J.L.); (S.J.); (M.G.); (T.C.); (S.P.); (M.-F.C.); (F.N.)
| | - Françoise Nau
- STLO, INRAE, Institut Agro, 35042 Rennes, France; (J.L.); (S.J.); (M.G.); (T.C.); (S.P.); (M.-F.C.); (F.N.)
| | - Simon C. Andrews
- School of Biological Sciences, Health and Life Sciences Building, University of Reading, Reading RG6 6AX, UK;
| | - Florence Baron
- STLO, INRAE, Institut Agro, 35042 Rennes, France; (J.L.); (S.J.); (M.G.); (T.C.); (S.P.); (M.-F.C.); (F.N.)
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8
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Baron F, Cochet MF, Alabdeh M, Guérin-Dubiard C, Gautier M, Nau F, Andrews SC, Bonnassie S, Jan S. Egg-White Proteins Have a Minor Impact on the Bactericidal Action of Egg White Toward Salmonella Enteritidis at 45°C. Front Microbiol 2020; 11:584986. [PMID: 33133053 PMCID: PMC7578404 DOI: 10.3389/fmicb.2020.584986] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2020] [Accepted: 09/18/2020] [Indexed: 02/05/2023] Open
Abstract
Salmonella enterica serovar Enteritidis is noted for its ability to survive the harsh antibacterial activity of egg white which is presumed to explain its occurrence as the major food-borne pathogen associated with the consumption of eggs and egg products. Liquid egg white is a major ingredient for the food industry but, because of its thermal fragility, pasteurization is performed at the modest temperature of 57°C (for 2–6 min). Unfortunately, such treatment does not lead to sufficient reduction in S. Enteritidis contamination, which is a clear health concern when the product is consumed without cooking. However, egg white is able to limit S. Enteritidis growth due to its alkaline pH, iron deficiency and multiple antimicrobial proteins. This anti-Salmonella activity of egg white is temperature dependent and becomes bactericidal once the incubation temperature exceeds 42°C. This property is exploited in the highly promising pasteurization treatment (42–45°C for 1–5 days) which achieves complete killing of S. Enteritidis. However, the precise mechanism and the role of the egg-white proteins are not fully understood. Here, the impact of exposure of S. Enteritidis to egg white-based media, with or without egg-white proteins (>10 kDa), under bactericidal conditions (45°C) was explored by measuring survival and global expression. Surprisingly, the bactericidal activity of egg white at 45°C was only slightly affected by egg-white proteins indicating that they play a minor role in the bactericidal activity observed. Moreover, egg-white proteins had minimal impact on the global-gene-expression response to egg white such that very similar, major regulatory responses (20% genes affected) were observed both with and without egg-white proteins following incubation for 45 min at 45°C. Egg-white proteins caused a significant change in expression for just 64 genes, including the psp and lysozyme-inhibitor responses genes which is suggestive of an early membrane perturbation effect. Such damage was supported by disruption of the proton motive force by egg-white proteins. In summary, the results suggest that low-mass components of egg white are largely responsible for the bactericidal activity of egg white at 45°C.
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Affiliation(s)
| | | | | | | | | | | | - Simon C Andrews
- School of Biological Sciences, University of Reading, Reading, United Kingdom
| | - Sylvie Bonnassie
- STLO, INRAE, Institut Agro, Rennes, France.,UFR Sciences de la Vie et de l'Environnement, Université de Rennes I, Rennes, France
| | - Sophie Jan
- STLO, INRAE, Institut Agro, Rennes, France
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9
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Wellawa DH, Allan B, White AP, Köster W. Iron-Uptake Systems of Chicken-Associated Salmonella Serovars and Their Role in Colonizing the Avian Host. Microorganisms 2020; 8:E1203. [PMID: 32784620 PMCID: PMC7465098 DOI: 10.3390/microorganisms8081203] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Revised: 07/30/2020] [Accepted: 07/31/2020] [Indexed: 01/09/2023] Open
Abstract
Iron is an essential micronutrient for most bacteria. Salmonella enterica strains, representing human and animal pathogens, have adopted several mechanisms to sequester iron from the environment depending on availability and source. Chickens act as a major reservoir for Salmonella enterica strains which can lead to outbreaks of human salmonellosis. In this review article we summarize the current understanding of the contribution of iron-uptake systems to the virulence of non-typhoidal S. enterica strains in colonizing chickens. We aim to address the gap in knowledge in this field, to help understand and define the interactions between S. enterica and these important hosts, in comparison to mammalian models.
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Affiliation(s)
- Dinesh H. Wellawa
- Vaccine & Infectious Disease Organization-International Vaccine Centre, University of Saskatchewan, 120 Veterinary Rd., Saskatoon, SK S7N 5E3, Canada; (D.H.W.); (B.A.); (A.P.W.)
- Department of Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK S7N 5B4, Canada
| | - Brenda Allan
- Vaccine & Infectious Disease Organization-International Vaccine Centre, University of Saskatchewan, 120 Veterinary Rd., Saskatoon, SK S7N 5E3, Canada; (D.H.W.); (B.A.); (A.P.W.)
| | - Aaron P. White
- Vaccine & Infectious Disease Organization-International Vaccine Centre, University of Saskatchewan, 120 Veterinary Rd., Saskatoon, SK S7N 5E3, Canada; (D.H.W.); (B.A.); (A.P.W.)
- Department of Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK S7N 5B4, Canada
| | - Wolfgang Köster
- Vaccine & Infectious Disease Organization-International Vaccine Centre, University of Saskatchewan, 120 Veterinary Rd., Saskatoon, SK S7N 5E3, Canada; (D.H.W.); (B.A.); (A.P.W.)
- Department of Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK S7N 5B4, Canada
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Chiok KLR, Shah DH. Identification of common highly expressed genes of Salmonella Enteritidis by in silico prediction of gene expression and in vitro transcriptomic analysis. Poult Sci 2019; 98:2948-2963. [PMID: 30953073 DOI: 10.3382/ps/pez119] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Accepted: 02/27/2019] [Indexed: 01/02/2023] Open
Abstract
Chickens are the reservoir host of Salmonella Enteritidis. Salmonella Enteritidis colonizes the gastro-intestinal tract of chickens and replicates within macrophages without causing clinically discernable illness. Persistence of S. Enteritidis in the hostile environments of intestinal tract and macrophages allows it to disseminate extra-intestinally to liver, spleen, and reproductive tract. Extra-intestinal dissemination into reproductive tract leads to contamination of internal contents of eggs, which is a major risk factor for human infection. Understanding the genes that contribute to S. Enteritidis persistence in the chicken host is central to elucidate the genetic basis of the unique pathobiology of this public health pathogen. The aim of this study was to identify a succinct set of genes associated with infection-relevant in vitro environments to provide a rational foundation for subsequent biologically-relevant research. We used in silico prediction of gene expression and RNA-seq technology to identify a core set of 73 S. Enteritidis genes that are consistently highly expressed in multiple S. Enteritidis strains cultured at avian physiologic temperature under conditions that represent intestinal and intracellular environments. These common highly expressed (CHX) genes encode proteins involved in bacterial metabolism, protein synthesis, cell-envelope biogenesis, stress response, and a few proteins with uncharacterized functions. Further studies are needed to dissect the contribution of these CHX genes to the pathobiology of S. Enteritidis in the avian host. Several of the CHX genes could serve as promising targets for studies towards the development of immunoprophylactic and novel therapeutic strategies to prevent colonization of chickens and their environment with S. Enteritidis.
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Affiliation(s)
- Kim Lam R Chiok
- Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA 99164-7040
| | - Devendra H Shah
- Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA 99164-7040
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11
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12
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Baron F, Bonnassie S, Alabdeh M, Cochet MF, Nau F, Guérin-Dubiard C, Gautier M, Andrews SC, Jan S. Global Gene-expression Analysis of the Response of Salmonella Enteritidis to Egg White Exposure Reveals Multiple Egg White-imposed Stress Responses. Front Microbiol 2017; 8:829. [PMID: 28553268 PMCID: PMC5428311 DOI: 10.3389/fmicb.2017.00829] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2017] [Accepted: 04/24/2017] [Indexed: 12/20/2022] Open
Abstract
Chicken egg white protects the embryo from bacterial invaders by presenting an assortment of antagonistic activities that combine together to both kill and inhibit growth. The key features of the egg white anti-bacterial system are iron restriction, high pH, antibacterial peptides and proteins, and viscosity. Salmonella enterica serovar Enteritidis is the major pathogen responsible for egg-borne infection in humans, which is partly explained by its exceptional capacity for survival under the harsh conditions encountered within egg white. However, at temperatures up to 42°C, egg white exerts a much stronger bactericidal effect on S. Enteritidis than at lower temperatures, although the mechanism of egg white-induced killing is only partly understood. Here, for the first time, the impact of exposure of S. Enteritidis to egg white under bactericidal conditions (45°C) is explored by global-expression analysis. A large-scale (18.7% of genome) shift in transcription is revealed suggesting major changes in specific aspects of S. Enteritidis physiology: induction of egg white related stress-responses (envelope damage, exposure to heat and alkalinity, and translation shutdown); shift in energy metabolism from respiration to fermentation; and enhanced micronutrient provision (due to iron and biotin restriction). Little evidence of DNA damage or redox stress was obtained. Instead, data are consistent with envelope damage resulting in cell death by lysis. A surprise was the high degree of induction of hexonate/hexuronate utilization genes, despite no evidence indicating the presence of these substrates in egg white.
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Affiliation(s)
- Florence Baron
- Agrocampus Ouest, UMR1253 Science et Technologie du Lait et de l'OeufRennes, France
- INRA, UMR1253 Science et Technologie du Lait et de l'OeufRennes, France
| | - Sylvie Bonnassie
- Agrocampus Ouest, UMR1253 Science et Technologie du Lait et de l'OeufRennes, France
- INRA, UMR1253 Science et Technologie du Lait et de l'OeufRennes, France
- Science de la Vie et de la Terre, Université de Rennes IRennes, France
| | - Mariah Alabdeh
- Agrocampus Ouest, UMR1253 Science et Technologie du Lait et de l'OeufRennes, France
- INRA, UMR1253 Science et Technologie du Lait et de l'OeufRennes, France
| | - Marie-Françoise Cochet
- Agrocampus Ouest, UMR1253 Science et Technologie du Lait et de l'OeufRennes, France
- INRA, UMR1253 Science et Technologie du Lait et de l'OeufRennes, France
| | - Françoise Nau
- Agrocampus Ouest, UMR1253 Science et Technologie du Lait et de l'OeufRennes, France
- INRA, UMR1253 Science et Technologie du Lait et de l'OeufRennes, France
| | - Catherine Guérin-Dubiard
- Agrocampus Ouest, UMR1253 Science et Technologie du Lait et de l'OeufRennes, France
- INRA, UMR1253 Science et Technologie du Lait et de l'OeufRennes, France
| | - Michel Gautier
- Agrocampus Ouest, UMR1253 Science et Technologie du Lait et de l'OeufRennes, France
- INRA, UMR1253 Science et Technologie du Lait et de l'OeufRennes, France
| | | | - Sophie Jan
- Agrocampus Ouest, UMR1253 Science et Technologie du Lait et de l'OeufRennes, France
- INRA, UMR1253 Science et Technologie du Lait et de l'OeufRennes, France
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Gast RK, Guraya R, Jones DR, Guard J, Anderson KE, Karcher DM. Colonization of internal organs by Salmonella serovars Heidelberg and Typhimurium in experimentally infected laying hens housed in enriched colony cages at different stocking densities. Poult Sci 2017; 96:1402-1409. [DOI: 10.3382/ps/pew375] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Accepted: 09/02/2016] [Indexed: 01/01/2023] Open
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Pesingi PK, Kumawat M, Behera P, Dixit SK, Agarwal RK, Goswami TK, Mahawar M. Protein-L-Isoaspartyl Methyltransferase (PIMT) Is Required for Survival of Salmonella Typhimurium at 42°C and Contributes to the Virulence in Poultry. Front Microbiol 2017; 8:361. [PMID: 28326072 PMCID: PMC5339242 DOI: 10.3389/fmicb.2017.00361] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Accepted: 02/21/2017] [Indexed: 01/07/2023] Open
Abstract
Poultry birds are asymptomatic reservoir of Salmonella Typhimurium (S. Typhimurium) but act as source of human infection for this bacterium. Inside the poultry, S. Typhimurium experiences several stresses, 42°C body temperature of birds is one of them. Proteins are highly susceptible to temperature mediated damage. Conversion of protein bound aspartate (Asp) residues to iso-aspartate (iso-Asp) is one of such modifications that occur at elevated temperature. Iso-Asp formation has been linked to protein inactivation and compromised cellular survival. Protein-L-isoaspartyl methyltransferase (PIMT) can repair iso-Asp back to Asp, thus enhances the cellular survival at elevated temperature. Here, we show that the pimt gene deletion strain of S. Typhimurium (Δpimt mutant strain) is hypersensitive to 42°C in vitro. The hypersusceptibility of Δpimt strain is partially reversed by plasmid based complementation (trans-complementation) of Δpimt strain. Following oral inoculation, Δpimt strain showed defective colonization in poultry caecum, and compromised dissemination to spleen and liver. Interestingly, we have observed three and half folds induction of the PIMT protein following exposure of S. Typhimurium to 42°C. Our data suggest a novel role of pimt gene in the survival of S. Typhimurium at elevated temperature and virulence.
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Affiliation(s)
- Pavan K Pesingi
- Division of Veterinary Public Health, Indian Veterinary Research Institute Izatnagar, India
| | - Manoj Kumawat
- Division of Biochemistry, Indian Veterinary Research Institute Izatnagar, India
| | - Pranatee Behera
- Division of Biochemistry, Indian Veterinary Research Institute Izatnagar, India
| | - Sunil K Dixit
- Division of Immunology, Indian Veterinary Research Institute Izatnagar, India
| | - Rajesh K Agarwal
- Division of Bacteriology and Mycology, Indian Veterinary Research Institute Izatnagar, India
| | - Tapas K Goswami
- Division of Immunology, Indian Veterinary Research Institute Izatnagar, India
| | - Manish Mahawar
- Division of Biochemistry, Indian Veterinary Research Institute Izatnagar, India
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Kilroy S, Raspoet R, Martel A, Bosseler L, Appia-Ayme C, Thompson A, Haesebrouck F, Ducatelle R, Van Immerseel F. Salmonella Enteritidis flagellar mutants have a colonization benefit in the chicken oviduct. Comp Immunol Microbiol Infect Dis 2017; 50:23-28. [PMID: 28131374 DOI: 10.1016/j.cimid.2016.11.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Revised: 07/28/2016] [Accepted: 11/07/2016] [Indexed: 10/20/2022]
Abstract
Egg borne Salmonella Enteritidis is still a major cause of human food poisoning. Eggs can become internally contaminated following colonization of the hen's oviduct. In this paper we aimed to analyze the role of flagella of Salmonella Enteritidis in colonization of the hen's oviduct. Using a transposon library screen we showed that mutants lacking functional flagella are significantly more efficient in colonizing the hen's oviduct in vivo. A micro-array analysis proved that transcription of a number of flagellar genes is down-regulated inside chicken oviduct cells. Flagella contain flagellin, a pathogen associated molecular pattern known to bind to Toll-like receptor 5, activating a pro-inflammatory cascade. In vitro tests using primary oviduct cells showed that flagellin is not involved in invasion. Using a ligated loop model, a diminished inflammatory reaction was seen in the oviduct resulting from injection of an aflagellated mutant compared to the wild-type. It is hypothesized that Salmonella Enteritidis downregulates flagellar gene expression in the oviduct and consequently prevents a flagellin-induced inflammatory response, thereby increasing its oviduct colonization efficiency.
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Affiliation(s)
- Sofie Kilroy
- Department of Pathology, Bacteriology and Avian Diseases, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, B-9820 Merelbeke, Belgium.
| | - Ruth Raspoet
- Department of Pathology, Bacteriology and Avian Diseases, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, B-9820 Merelbeke, Belgium.
| | - An Martel
- Department of Pathology, Bacteriology and Avian Diseases, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, B-9820 Merelbeke, Belgium.
| | - Leslie Bosseler
- Department of Pathology, Bacteriology and Avian Diseases, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, B-9820 Merelbeke, Belgium.
| | - Corinne Appia-Ayme
- John Innes Centre, Norwich Research Park, Colney Ln, Norwich NR4 7UH, Norwich, United Kingdom; Institute of Food Research, Norwich Research Park, Colney Ln, Norwich NR4 7UA, United Kingdom.
| | - Arthur Thompson
- Institute of Food Research, Norwich Research Park, Colney Ln, Norwich NR4 7UA, United Kingdom.
| | - Freddy Haesebrouck
- Department of Pathology, Bacteriology and Avian Diseases, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, B-9820 Merelbeke, Belgium.
| | - Richard Ducatelle
- Department of Pathology, Bacteriology and Avian Diseases, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, B-9820 Merelbeke, Belgium.
| | - Filip Van Immerseel
- Department of Pathology, Bacteriology and Avian Diseases, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, B-9820 Merelbeke, Belgium.
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Abstract
Salmonella Enteritidis (SE) is the predominant cause of the food-borne salmonellosis in humans, in part because this serotype has the unique ability to contaminate chicken eggs without causing discernible illness in the infected birds. Attempts to develop effective vaccines and eradicate SE from chickens are undermined by significant limitations in our current understanding of the genetic basis of pathogenesis of SE in this reservoir host. In this chapter, we summarize the infection kinetics and provide an overview of the current understanding of genetic factors underlying SE infection in the chicken host. We also discuss the important knowledge gaps that, if addressed, will improve our understanding of the complex biology of SE in young chickens and in egg laying hens.
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McWhorter AR, Chousalkar KK. In vitro invasive capacity of Salmonella strains into sections of the layer hen oviduct. Vet Microbiol 2016; 192:135-144. [DOI: 10.1016/j.vetmic.2016.07.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2016] [Revised: 06/26/2016] [Accepted: 07/07/2016] [Indexed: 10/21/2022]
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18
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Gast RK, Guraya R, Jones DR, Anderson KE, Karcher DM. Colonization of internal organs by Salmonella Enteritidis in experimentally infected laying hens housed in enriched colony cages at different stocking densities. Poult Sci 2016; 95:1363-9. [DOI: 10.3382/ps/pew037] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2015] [Accepted: 01/08/2016] [Indexed: 01/12/2023] Open
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Babu US, Harrison LM, Patel IR, Ramirez GA, Williams KM, Pereira M, Balan KV. Differential antibacterial response of chicken granulosa cells to invasion by Salmonella serovars. Poult Sci 2016; 95:1370-9. [DOI: 10.3382/ps/pew050] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Accepted: 12/14/2015] [Indexed: 01/27/2023] Open
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20
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Jakočiūnė D, Herrero-Fresno A, Jelsbak L, Olsen JE. Highly expressed amino acid biosynthesis genes revealed by global gene expression analysis of Salmonella enterica serovar Enteritidis during growth in whole egg are not essential for this growth. Int J Food Microbiol 2016; 224:40-6. [DOI: 10.1016/j.ijfoodmicro.2016.02.015] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Revised: 02/12/2016] [Accepted: 02/21/2016] [Indexed: 01/17/2023]
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21
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Intramacrophage Infection Reinforces the Virulence of Edwardsiella tarda. J Bacteriol 2016; 198:1534-42. [PMID: 26953340 DOI: 10.1128/jb.00978-15] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2015] [Accepted: 03/01/2016] [Indexed: 01/30/2023] Open
Abstract
UNLABELLED Edwardsiella tarda is an important pathogenic bacterium that can replicate in macrophages. However, how the intramacrophage infection process affects the virulence of this bacterium is essentially unknown. Here, we show that E. tarda replicates and induces a caspase-1-dependent cell pyroptosis in a murine macrophage model. Via pyroptosis, intracellular E. tarda escapes to the extracellular milieu, forming a unique bacterial population. Being different from the bacteria cultured alone, this unique population possesses a reprogrammed transcriptional profile, particularly with upregulated type III secretion system (T3SS)/T6SS cluster genes. Subsequent studies revealed that the macrophage-released population gains enhanced infectivity for host epithelial cells and increases resistance to multiple host defenses and hence displays significantly promoted virulence in vivo Further studies indicated that T3SS is essentially required for the macrophage infection process, while T6SS contributes to infection-induced bacterial virulence. Altogether, this work demonstrates that E. tarda can utilize macrophages as a niche for virulence priming and for spreading infection, suggesting a positive role for intramacrophage infection in bacterial pathogenesis. IMPORTANCE Many pathogens can replicate in macrophages, which is crucial for their pathogenesis. To survive in the macrophage cell, pathogens are likely to require fitness genes to counteract multiple host-killing mechanisms. Here, Edwardsiella tarda is proved to exit from macrophages during infection. This macrophage-released population displays a reprogrammed transcriptional profile with significantly upregulated type III secretion system (T3SS)/T6SS-related genes. Furthermore, both enhanced infectivity in epithelial cells and activated resistance to complex host defenses were conferred on this macrophage-primed population, which consequently promoted the full virulence of E. tarda in vivo Our work provides evidence that E. tarda can utilize macrophages as a niche for virulence priming and for spreading infection, highlighting the importance of the intramacrophage infection cycle for the pathogenesis of E. tarda.
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