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Chang G, Luo Z, Zhang Y, Xu X, Zhou T, Chen D, Li L, Wang X. Electron beam irradiation degrades the toxicity and alters the protein structure of Staphylococcus aureus alpha-hemolysin. Int J Biol Macromol 2023; 246:125608. [PMID: 37392914 DOI: 10.1016/j.ijbiomac.2023.125608] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2023] [Revised: 06/25/2023] [Accepted: 06/27/2023] [Indexed: 07/03/2023]
Abstract
α-Hemolysin (Hla) is a potent pore-forming toxin (PFT) produced by Staphylococcus aureus that exacerbates the pathogenesis of S. aureus enterotoxicity and plays a role in population food poisoning. Hla lyses cells by binding to host cell membranes and oligomerizing to form heptameric structures, thereby disrupting the cell barrier. Although the broad bactericidal effect of electron beam irradiation (EBI) has been demonstrated whether it has a damaging or degrading effect on Hla's remains unknown. In this study, EBI was found to have the effect of altering the secondary structure of Hla proteins, verifying that the damaging effect of EBI-treated Hla on intestinal and skin epithelial cell barriers was significantly reduced. It was noted by hemolysis and protein interactions that EBI treatment significantly disrupted the binding of Hla to its high-affinity receptor, but did not affect the binding between Hla monomers to form heptamers. Thus, EBI can effectively reduce the threat of Hla to food safety.
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Affiliation(s)
- Guanhong Chang
- College of Food Science and Engineering, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Zonghong Luo
- College of Food Science and Engineering, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Yao Zhang
- College of Food Science and Engineering, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Xu Xu
- College of Food Science and Engineering, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Ting Zhou
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - DiShi Chen
- Sichuan Animal Disease Prevention and Control Center, Chengdu 610041, China
| | - Li Li
- Sichuan Animal Disease Prevention and Control Center, Chengdu 610041, China
| | - Xin Wang
- College of Food Science and Engineering, Northwest A&F University, Yangling, Shaanxi 712100, China.
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Chang G, Luo Z, Zhang Y, Xu X, Zhou T, Wang X. Effect and Mechanism of Eliminating Staphylococcus aureus by Electron Beam Irradiation and Reducing the Toxicity of Its Metabolites. Appl Environ Microbiol 2023; 89:e0207522. [PMID: 36847554 PMCID: PMC10057028 DOI: 10.1128/aem.02075-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Accepted: 01/19/2023] [Indexed: 03/01/2023] Open
Abstract
The purpose of this study was to evaluate the mechanism of sterilization of Staphylococcus aureus by electron beam irradiation (0.5-, 1-, 2-, 4-, and 6-kGy treatments) and whether it reduces the toxicity of its fermentation supernatant. In this study, we investigated the mechanism of sterilization of S. aureus by electron beam irradiation using colony count, membrane potential, intracellular ATP, and UV absorbance measurements; we used hemolytic, cytotoxic, and suckling mouse wound models to verify that electron beam irradiation reduced the toxicity of the S. aureus fermentation supernatant. The results showed that 2 kGy of electron beam irradiation treatment completely inactivated S. aureus in suspension culture, and 4 kGy inactivated cells in S. aureus biofilms. This study suggests that the bactericidal effect of electron beam irradiation on S. aureus may be attributed to reversible damage to the cytoplasmic membrane, resulting in its leakage and the significant degradation of genomic DNA. The combined results of hemolytic, cytotoxic, and suckling mouse wound models demonstrated that the toxicity of S. aureus metabolites was significantly reduced when the electron beam irradiation dose was 4 kGy. In summary, electron beam irradiation has the potential to control S. aureus and reduce its toxic metabolites in food. IMPORTANCE Electron beam irradiation of >1 kGy damaged the cytoplasmic membrane, and reactive oxygen species (ROS) penetrated the cells. Electron beam irradiation of >4 kGy reduces the combined toxicity of virulent proteins produced by Staphylococcus aureus. Electron beam irradiation of >4 kGy can be used to inactivate Staphylococcus aureus and biofilms on milk.
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Affiliation(s)
- Guanhong Chang
- College of Food Science and Engineering, Northwest A&F University, Yangling, Shaanxi, China
| | - Zonghong Luo
- College of Food Science and Engineering, Northwest A&F University, Yangling, Shaanxi, China
| | - Yao Zhang
- College of Food Science and Engineering, Northwest A&F University, Yangling, Shaanxi, China
| | - Xu Xu
- College of Food Science and Engineering, Northwest A&F University, Yangling, Shaanxi, China
| | - Ting Zhou
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, China
| | - Xin Wang
- College of Food Science and Engineering, Northwest A&F University, Yangling, Shaanxi, China
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Scaturro M, Barello C, Giusti MD, Fontana S, Pinci F, Giuffrida MG, Ricci ML. Identification and characterization of genes, encoding the 3-hydroxybutyrate dehydrogenase and a putative lipase, in an avirulent spontaneousLegionella pneumophilaserogroup 6 mutant. APMIS 2014; 123:330-41. [DOI: 10.1111/apm.12349] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2014] [Accepted: 10/22/2014] [Indexed: 12/23/2022]
Affiliation(s)
- Maria Scaturro
- Department of Infectious Parasitic Immune-mediated Diseases; Istituto Superiore di Sanità; Rome Italy
| | - Cristina Barello
- Istituto di Scienze delle Produzioni Alimentari; CNR; Sezione di Torino; Colleretto Giacosa (TO) Italy
| | - Melania De Giusti
- Department of Infectious Parasitic Immune-mediated Diseases; Istituto Superiore di Sanità; Rome Italy
| | - Stefano Fontana
- Department of Infectious Parasitic Immune-mediated Diseases; Istituto Superiore di Sanità; Rome Italy
| | - Federica Pinci
- Department of Infectious Parasitic Immune-mediated Diseases; Istituto Superiore di Sanità; Rome Italy
| | - Maria Gabriella Giuffrida
- Istituto di Scienze delle Produzioni Alimentari; CNR; Sezione di Torino; Colleretto Giacosa (TO) Italy
| | - Maria Luisa Ricci
- Department of Infectious Parasitic Immune-mediated Diseases; Istituto Superiore di Sanità; Rome Italy
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Scaturro M, Meschini S, Arancia G, Stefano F, Ricci ML. Characterization of a spontaneous avirulent mutant of Legionella pneumophila Serogroup 6: Evidence of DotA and flagellin involvement in the loss of virulence. J Microbiol 2010; 47:768-73. [DOI: 10.1007/s12275-009-0103-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2009] [Accepted: 07/16/2009] [Indexed: 12/27/2022]
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Ricci ML, Torosantucci A, Scaturro M, Chiani P, Baldassarri L, Pastoris MC. Induction of protective immunity by Legionella pneumophila flagellum in an A/J mouse model. Vaccine 2006; 23:4811-20. [PMID: 16005118 DOI: 10.1016/j.vaccine.2005.05.013] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2004] [Accepted: 05/16/2005] [Indexed: 10/25/2022]
Abstract
The capacity of a purified preparation of Legionella pneumophila flagella (FLA) to induce protective immune responses was studied in an A/J mouse model. Animals immunized with FLA promptly mounted an anti-FLA antibody response and also developed a strong activation of both innate and adaptive cell-mediated immunity, as shown by an early release of pro-inflammatory cytokines in the peritoneal cavity, and by a positive cutaneous delayed-type hypersensitivity reaction and in vitro splenic lymphocyte proliferation in response to FLA antigens. Mice treated with FLA either i.v. or i.p. also survived (100% rate) a lethal i.p. challenge with L. pneumophila. Protection induced by FLA lasted for at least 30 days after treatment, but less than 60, and was effective against the challenge with different serogroups of L. pneumophila. Resistance conferred by FLA immunization could be partially transferred to naïve animals by the adoptive transfer of immune splenocytes but not by passive immunization with anti-FLA iperimmune sera. The capacity to induce protective immunity was specifically attributable to flagellar components, as demonstrated by the lack of protection in mice immunized with a sham flagella preparation from a non-flagellated bacterial strain or with protease-digested FLA. In addition, heat-denatured FLA was inactive, suggesting loss of immunogenicity following denaturation. The present study provides evidence that L. pneumophila flagellum is strongly immunogenic and capable to stimulate, without adjuvants, early natural and acquired, T-cell-mediated immune responses and to induce significant protection against a lethal bacterial challenge in A/J mice. Antigenic characterization of this bacterial organelle and elucidation of mechanisms underlying flagella-induced protection would be of great value in understanding the immunopathogenesis of the disease and in developing possible therapeutic strategies for human legionellosis.
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Affiliation(s)
- Maria Luisa Ricci
- Department of Infectious, Parasitic and Immune-Mediated Diseases, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Roma, Italy.
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Schiavoni G, Mauri C, Carlei D, Belardelli F, Pastoris MC, Proietti E. Type I IFN protects permissive macrophages from Legionella pneumophila infection through an IFN-gamma-independent pathway. THE JOURNAL OF IMMUNOLOGY 2004; 173:1266-75. [PMID: 15240719 DOI: 10.4049/jimmunol.173.2.1266] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Legionella pneumophila is an intracellular pathogen whose replication in macrophages is mainly controlled by IFN-gamma. Freshly isolated peritoneal macrophages elicited in vivo with thioglycolate (TG) from A/J mice are highly permissive to L. pneumophila growth in vitro, while TG-elicited macrophages from CD1 mice are resistant. In this study, we show that when CD1 TG-macrophages are cultured for 7 days, they become permissive to Legionella infection. We demonstrate that treatment with type I IFN (IFN-alphabeta) totally inhibits the growth of L. pneumophila in both freshly isolated A/J and in vitro-aged CD1 TG-macrophages. IFN-alphabeta protective effect on permissive macrophages was comparable to that induced by IFN-gamma. Even low doses of either IFN-alpha or IFN-beta alone were effective in inhibiting L. pneumophila multiplication in macrophage cultures. Notably, treatment of resistant, freshly isolated CD1 TG-macrophages with Ab to mouse IFN-alphabeta significantly enhanced their susceptibility to Legionella infection in vitro, thus implying a role of endogenous IFN-alphabeta in mediating the natural resistance of macrophages to L. pneumophila infection. Finally, addition of anti-IFN-gamma-neutralizing Ab did not restore Legionella growth in IFN-alpha- or IFN-beta-treated A/J or CD1 permissive macrophages, indicating that IFN-alphabeta effect was not mediated by IFN-gamma. This observation was further confirmed by the finding that IFN-alphabeta was effective in inhibiting L. pneumophila replication in macrophages from IFN-gamma receptor-deficient mice. Taken together, our results provide the first evidence for a role of IFN-alphabeta in the control of L. pneumophila infection in mouse models of susceptible macrophages and suggest the existence of different pathways for the control of intracellular bacteria in macrophages.
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Guo BP, Mekalanos JJ. Rapid genetic analysis of Helicobacter pylori gastric mucosal colonization in suckling mice. Proc Natl Acad Sci U S A 2002; 99:8354-9. [PMID: 12060779 PMCID: PMC123071 DOI: 10.1073/pnas.122244899] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Previously described animal models for Helicobacter pylori infection have been limited by cumbersome host requirements (e.g., germ-free conditions or unusual species) or are applicable to only special subsets of H. pylori strains (e.g., fresh clinical isolates or animal-adapted derivatives). Here, we report that 5- to 6-day-old outbred CD-1 (ICR) suckling mice support 24-h colonization of all H. pylori strains tested (SS1, 26695 SmR-1, 43504 SmR-1, and G27 SmR-1), including lab-passaged strains that cannot be adapted for colonization of adult animals. Total colony-forming units (cfu) recovered from infection with lab-passaged strains did not differ from those with mouse-adapted SS1. We also tested this model's ability to detect colonization defects in strains carrying mutations in known virulence genes by coinfecting with wild-type H. pylori and measuring differential recovery. This competition assay identified colonization defects in several classes of known attenuated mutants, including those defective in acid resistance (ureA), metabolism (frdA), motility (motB), and chemotaxis (cheY). A mutant defective in copA (copper transporting P-type ATPase) is nonattenuated in adult and infant mice. Possibly because of the limited duration of infection, our model did not identify defects in vacuolating cytotoxin (vacA) or gamma-glutamyltranspeptidase (ggt) as attenuating, in contrast to results from other animal models. We also identified a new virulence gene (HP0507) encoding a conserved hypothetical protein, which is important for colonization in our model. The suckling mouse model offers a rapid method to identify colonization defects in any H. pylori strain and may have utility as a new tool for studying immunity to primary infection.
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Affiliation(s)
- Betty P Guo
- Department of Microbiology and Molecular Genetics, Harvard Medical School, 200 Longwood Avenue, Armenise 408, Boston, MA 02115
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