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Kudva IT, Biernbaum EN, Cassmann ED, Palmer MV. Bovine Rectoanal Junction In Vitro Organ Culture Model System to Study Shiga Toxin-Producing Escherichia coli Adherence. Microorganisms 2023; 11:1289. [PMID: 37317263 DOI: 10.3390/microorganisms11051289] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Revised: 04/27/2023] [Accepted: 05/06/2023] [Indexed: 06/16/2023] Open
Abstract
Studies evaluating the interactions between Shiga toxin-producing Escherichia coli O157:H7 (O157) and the bovine recto-anal junction (RAJ) have been limited to either in vitro analyses of bacteria, cells, or nucleic acids at the RAJ, providing limited information. Alternatively, expensive in vivo studies in animals have been conducted. Therefore, our objective was to develop a comprehensive in vitro organ culture system of the RAJ (RAJ-IVOC) that accurately represents all cell types present in the RAJ. This system would enable studies that yield results similar to those observed in vivo. Pieces of RAJ tissue, obtained from unrelated cattle necropsies, were assembled and subjected to various tests in order to determine the optimal conditions for assaying bacterial adherence in a viable IVOC. O157 strain EDL933 and E. coli K12 with known adherence differences were used to standardize the RAJ-IVOC adherence assay. Tissue integrity was assessed using cell viability, structural cell markers, and histopathology, while the adherence of bacteria was evaluated via microscopy and culture methods. DNA fingerprinting verified the recovered bacteria against the inoculum. When the RAJ-IVOC was assembled in Dulbecco's Modified Eagle Medium, maintained at a temperature of 39 °C with 5% CO2 and gentle shaking for a duration of 3-4 h, it successfully preserved tissue integrity and reproduced the expected adherence phenotype of the bacteria being tested. The RAJ-IVOC model system provides a convenient method to pre-screen multiple bacteria-RAJ interactions prior to in vivo experiments, thereby reducing animal usage.
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Affiliation(s)
- Indira T Kudva
- Food Safety and Enteric Pathogens Research Unit, National Animal Disease Center, Agricultural Research Service, U.S. Department of Agriculture, Ames, IA 50010, USA
| | - Erika N Biernbaum
- Food Safety and Enteric Pathogens Research Unit, National Animal Disease Center, Agricultural Research Service, U.S. Department of Agriculture, Ames, IA 50010, USA
- Oak Ridge Institute for Science and Education, Oak Ridge, TN 37830, USA
| | - Eric D Cassmann
- Virus and Prion Research Unit, National Animal Disease Center, Agricultural Research Service, U.S. Department of Agriculture, Ames, IA 50010, USA
| | - Mitchell V Palmer
- Infectious Bacterial Diseases Research Unit, National Animal Disease Center, Agricultural Research Service, U.S. Department of Agriculture, Ames, IA 50010, USA
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Mucosal IFNγ production and potential role in protection in Escherichia coli O157:H7 vaccinated and challenged cattle. Sci Rep 2021; 11:9769. [PMID: 33963240 PMCID: PMC8105325 DOI: 10.1038/s41598-021-89113-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Accepted: 04/15/2021] [Indexed: 11/16/2022] Open
Abstract
Shiga-toxin producing Escherichia coli O157:H7 (O157)-based vaccines can provide a potential intervention strategy to limit foodborne zoonotic transmission of O157. While the peripheral antibody response to O157 vaccination has been characterized, O157-specific cellular immunity at the rectoanal junction (RAJ), a preferred site for O157 colonization, remains poorly described. Vaccine induced mucosal O157-specific antibodies likely provide some protection, cellular immune responses at the RAJ may also play a role in protection. Distinct lymphoid follicles were increased in the RAJ of vaccinated/challenged animals. Additionally, increased numbers of interferon (IFN)γ-producing cells and γδ + T cells were detected in the follicular region of the RAJ of vaccinated/challenged animals. Likewise, adjuvanted-vaccine formulation is critical in immunogenicity of the O157 parenteral vaccine. Local T cell produced IFNγ may impact epithelial cells, subsequently limiting O157 adherence, which was demonstrated using in vitro attachment assays with bovine epithelial cells. Thus, distinct immune changes induced at the mucosa of vaccinated and challenged animals provide insight of mechanisms associated with limiting O157 fecal shedding. Enhancing mucosal immunity may be critical in the further development of efficacious vaccines for controlling O157 in ruminants and thus limiting O157 transmission to humans.
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The Escherichia coli O157:H7 carbon starvation-inducible lipoprotein Slp contributes to initial adherence in vitro via the human polymeric immunoglobulin receptor. PLoS One 2019; 14:e0216791. [PMID: 31188867 PMCID: PMC6561548 DOI: 10.1371/journal.pone.0216791] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2018] [Accepted: 04/29/2019] [Indexed: 01/19/2023] Open
Abstract
Escherichia coli O157:H7 is the most well-studied serotype of the enterohemorrhagic E. coli (EHEC) class of E. coli intestinal pathogens and is responsible for many outbreaks of serious food-borne illness worldwide each year. Adherence mechanisms are a critical component of its pathogenesis, persistence in natural reservoirs, and environmental contamination. E. coli O157:H7 has a highly effective virulence operon, the Locus of Enterocyte Effacement (LEE), and its encoded intimate adherence mechanism is well characterized. However, factors involved in the preceding initial attachment are not well understood. In this study, we propose a mechanism of initial adherence used by E. coli O157:H7 in vitro. We describe a bacterial protein not previously reported to be involved in adherence, Slp, and its interactions with the human host protein polymeric immunoglobulin receptor (pIgR). The human pIgR has previously been shown to act as an adherence receptor for some mucosal pathogens and is highly expressed in the intestine. Following observation of significant colocalization between E. coli O157:H7 bacteria and pIgR location on Caco-2 cells, a co-immunoprecipitation (Co-IP) assay using a human recombinant Fc-tagged pIgR protein led to the identification of this protein. Disruption of Slp expression in E. coli O157:H7, through deletion of its encoding gene slp, produced a significant adherence deficiency to Caco-2 cells at early time points associated with initial adherence. Plasmid complementation of the slp gene fully restored the wild-type phenotype. Furthermore, immunofluorescence microscopy revealed evidence that this interaction is specific to the pathogenic strains of E. coli tested and not the nonpathogenic control strain E. coli K12. Additionally, deletion of slp gene resulted in the absence of the corresponding protein band in further Co-IP assays, while the plasmid-encoded slp gene complementation of the deletion mutant strain restored the wild-type pattern. These data support the proposal that Slp directly contributes to initial adherence, with the pIgR protein as its proposed receptor.
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Kieckens E, Rybarczyk J, Li RW, Vanrompay D, Cox E. Potential immunosuppressive effects of Escherichia coli O157:H7 experimental infection on the bovine host. BMC Genomics 2016; 17:1049. [PMID: 28003017 PMCID: PMC5178093 DOI: 10.1186/s12864-016-3374-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Accepted: 12/05/2016] [Indexed: 01/05/2023] Open
Abstract
BACKGROUND Enterohaemorrhagic Escherichia coli (EHEC), like E. coli O157:H7 are frequently detected in bovine faecal samples at slaughter. Cattle do not show clinical symptoms upon infection, but for humans the consequences after consuming contaminated beef can be severe. The immune response against EHEC in cattle cannot always clear the infection as persistent colonization and shedding in infected animals over a period of months often occurs. In previous infection trials, we observed a primary immune response after infection which was unable to protect cattle from re-infection. These results may reflect a suppression of certain immune pathways, making cattle more prone to persistent colonization after re-infection. To test this, RNA-Seq was used for transcriptome analysis of recto-anal junction tissue and ileal Peyer's patches in nine Holstein-Friesian calves in response to a primary and secondary Escherichia coli O157:H7 infection with the Shiga toxin (Stx) negative NCTC12900 strain. Non-infected calves served as controls. RESULTS In tissue of the recto-anal junction, only 15 genes were found to be significantly affected by a first infection compared to 1159 genes in the ileal Peyer's patches. Whereas, re-infection significantly changed the expression of 10 and 17 genes in the recto-anal junction tissue and the Peyer's patches, respectively. A significant downregulation of 69 immunostimulatory genes and a significant upregulation of seven immune suppressing genes was observed. CONCLUSIONS Although the recto-anal junction is a major site of colonization, this area does not seem to be modulated upon infection to the same extent as ileal Peyer's patches as the changes in gene expression were remarkably higher in the ileal Peyer's patches than in the recto-anal junction during a primary but not a secondary infection. We can conclude that the main effect on the transcriptome was immunosuppression by E. coli O157:H7 (Stx-) due to an upregulation of immune suppressive effects (7/12 genes) or a downregulation of immunostimulatory effects (69/94 genes) in the ileal Peyer's patches. These data might indicate that a primary infection promotes a re-infection with EHEC by suppressing the immune function.
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Affiliation(s)
- E. Kieckens
- Laboratory of Immunology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium
- Laboratory of Immunology and Animal Biotechnology, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Ghent, Belgium
| | - J. Rybarczyk
- Laboratory of Immunology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium
- Laboratory of Immunology and Animal Biotechnology, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Ghent, Belgium
| | - R. W. Li
- USDA-ARS, Bovine Functional Genomics Laboratory, Beltsville, MD USA
| | - D. Vanrompay
- Laboratory of Immunology and Animal Biotechnology, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Ghent, Belgium
| | - E. Cox
- Laboratory of Immunology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium
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Strain-dependent cellular immune responses in cattle following Escherichia coli O157:H7 colonization. Infect Immun 2014; 82:5117-31. [PMID: 25267838 DOI: 10.1128/iai.02462-14] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Enterohemorrhagic Escherichia coli (EHEC) O157:H7 causes hemorrhagic diarrhea and potentially fatal renal failure in humans. Ruminants are considered to be the primary reservoir for human infection. Vaccines that reduce shedding in cattle are only partially protective, and their underlying protective mechanisms are unknown. Studies investigating the response of cattle to colonization generally focus on humoral immunity, leaving the role of cellular immunity unclear. To inform future vaccine development, we studied the cellular immune responses of cattle during EHEC O157:H7 colonization. Calves were challenged either with a phage type 21/28 (PT21/28) strain possessing the Shiga toxin 2a (Stx2a) and Stx2c genes or with a PT32 strain possessing the Stx2c gene only. T-helper cell-associated transcripts at the terminal rectum were analyzed by reverse transcription-quantitative PCR (RT-qPCR). Induction of gamma interferon (IFN-γ) and T-bet was observed with peak expression of both genes at 7 days in PT32-challenged calves, while upregulation was delayed, peaking at 21 days, in PT21/28-challenged calves. Cells isolated from gastrointestinal lymph nodes demonstrated antigen-specific proliferation and IFN-γ release in response to type III secreted proteins (T3SPs); however, responsiveness was suppressed in cells isolated from PT32-challenged calves. Lymph node cells showed increased expression of the proliferation marker Ki67 in CD4(+) T cells from PT21/28-challenged calves, NK cells from PT32-challenged calves, and CD8(+) and γδ T cells from both PT21/28- and PT32-challenged calves following ex vivo restimulation with T3SPs. This study demonstrates that cattle mount cellular immune responses during colonization with EHEC O157:H7, the temporality of which is strain dependent, with further evidence of strain-specific immunomodulation.
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Real-time PCR methodology for selective detection of viable Escherichia coli O157:H7 cells by targeting Z3276 as a genetic marker. Appl Environ Microbiol 2012; 78:5297-304. [PMID: 22635992 DOI: 10.1128/aem.00794-12] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The goal of this study was to develop a sensitive, specific, and accurate method for the selective detection of viable Escherichia coli O157:H7 cells in foods. A unique open reading frame (ORF), Z3276, was identified as a specific genetic marker for the detection of E. coli O157:H7. We developed a real-time PCR assay with primers and probe targeting ORF Z3276 and confirmed that this assay was sensitive and specific for E. coli O157:H7 strains (n = 298). Using this assay, we can detect amounts of genomic DNA of E. coli O157:H7 as low as a few CFU equivalents. Moreover, we have developed a new propidium monoazide (PMA)-real-time PCR protocol that allows for the clear differentiation of viable from dead cells. In addition, the protocol was adapted to a 96-well plate format for easy and consistent handling of a large number of samples. Amplification of DNA from PMA-treated dead cells was almost completely inhibited, in contrast to the virtually unaffected amplification of DNA from PMA-treated viable cells. With beef spiked simultaneously with 8 × 10(7) dead cells/g and 80 CFU viable cells/g, we were able to selectively detect viable E. coli O157:H7 cells with an 8-h enrichment. In conclusion, this PMA-real-time PCR assay offers a sensitive and specific means to selectively detect viable E. coli O157:H7 cells in spiked beef. It also has the potential for high-throughput selective detection of viable E. coli O157:H7 cells in other food matrices and, thus, will have an impact on the accurate microbiological and epidemiological monitoring of food safety and environmental sources.
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Verotoxin-2 activates mitogen-activated protein kinases in bovine adherent peripheral blood mononuclear cells. J Comp Pathol 2011; 147:20-3. [PMID: 22014416 DOI: 10.1016/j.jcpa.2011.08.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2011] [Revised: 08/11/2011] [Accepted: 08/19/2011] [Indexed: 11/20/2022]
Abstract
The effects of verotoxin (VT) on the mitogen-activated protein (MAP) kinase signalling pathways were investigated in bovine adherent peripheral blood mononuclear cells (PBMCs). VT2 stimulated a transient activation of both p38 MAP kinase and extracellular-regulated kinase (ERK) and stimulated an increase in tumour necrosis factor-α release from PBMCs. Bovine PBMCs react with very similar kinetics to human peripheral blood monocytes, despite the gross differences in disease outcome of the two species on infection with verotoxigenic Escherichia coli.
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Al-Qadiri HM, Lu X, Al-Alami NI, Rasco BA. Survival of Escherichia coli O157:H7 and Campylobacter jejuni in bottled purified drinking water under different storage conditions. J Food Prot 2011; 74:254-60. [PMID: 21333145 DOI: 10.4315/0362-028x.jfp-10-368] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Survival of Escherichia coli O157:H7 and Campylobacter jejuni that were separately inoculated into bottled purified drinking water was investigated during storage at 22, 4, and -18 °C for 5, 7, and 2 days, respectively. Two inoculation levels were used, 1 and 10 CFU/ml (10(2) and 10(3) CFU/100 ml). In samples inoculated with 10(2) CFU/100 ml, C. jejuni was not detectable (>2-log reduction) after storage under the conditions specified above. E. coli O157:H7 was detected on nonselective and selective media at log reductions of 1.08 to 1.25 after storage at 22 °C, 1.19 to 1.56 after storage at 4 °C, and 1.54 to 1.98 after storage at -18 °C. When the higher inoculation level of 10(3) CFU/100 ml was used, C. jejuni was able to survive at 22 and 4 °C, with 2.25- and 2.17-log reductions, respectively, observed on nonselective media. At these higher inoculation levels, E. coli O157:H7 was detectable at 22, 4, and -18 °C, with log reductions of 0.76, 0.97, and 1.21, respectively, achieved on nonselective media. Additionally, E. coli O157:H7 showed significant differences in culturability (P<0.05) on the nonselective and selective culture media under the different storage conditions, with storage at -18 °C for 2 days being the treatment most inhibiting. The percentage of sublethal injury of E. coli O157:H7 ranged from ∼33 to 75%, indicating that microbial examination of bottled water must be done carefully, otherwise false-negative results or underestimation of bacterial numbers could pose a health risk when low levels of pathogens are present.
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Affiliation(s)
- Hamzah M Al-Qadiri
- Department of Nutrition and Food Technology, Faculty of Agriculture, The University of Jordan, Amman 11942, Jordan.
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Ray PC, Yu H, Fu PP. Nanogold-based sensing of environmental toxins: excitement and challenges. JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH. PART C, ENVIRONMENTAL CARCINOGENESIS & ECOTOXICOLOGY REVIEWS 2011; 29:52-89. [PMID: 21424976 DOI: 10.1080/10590501.2011.551315] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
There have been tremendous advances in the past ten years on the development of various nanomaterials-based sensors for detection of environmental toxins. Nanogold is of special interest because of its unique shape- and size-dependent optical properties, hyper-quenching ability, super surface-enhanced Raman and dynamic light scattering, and surface-modifiability by small organic molecules and biomolecules. These unique optical properties of nanogold have been explored for ultra-sensitive detection, while its surface-modifiability has been explored for selectivity. In general, the nanogold-based sensors are highly selective and sensitive along with simple sample preparation and sensor design. In this review article, we intend to capture some of the recent advances in nanogold-based sensor development and mechanistic studies, especially for bacteria, heavy metals, and nitroaromatic compounds. Undoubtedly, these developments will generate a lot of excitement for environmental scientists and toxicologists as well as the general public.
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Affiliation(s)
- Paresh Chandra Ray
- Department of Chemistry and Biochemistry, Jackson State University, Jackson, MS 39217, USA.
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Gene expression in the digestive tissues of ruminants and their relationships with feeding and digestive processes. Animal 2010; 4:993-1007. [DOI: 10.1017/s1751731109991285] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Singh AK, Senapati D, Wang S, Griffin J, Neely A, Candice P, Naylor KM, Varisli B, Kalluri JR, Ray PC. Gold Nanorod Based Selective Identification of Escherichia coli Bacteria Using Two-Photon Rayleigh Scattering Spectroscopy. ACS NANO 2009; 3:1906-12. [PMID: 19572619 PMCID: PMC2888863 DOI: 10.1021/nn9005494] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The presence of E. coli in foodstuffs and drinking water is a chronic worldwide problem. The worldwide food production industry is worth about U.S. $578 billion, and the demand for biosensors to detect pathogens and pollutants in foodstuffs is growing day by day. Driven by the need, we report for the first time that two-photon Rayleigh scattering (TPRS) properties of gold nanorods can be used for rapid, highly sensitive and selective detection of Escherichia coli bacteria from aqueous solution, without any amplification or enrichment in 50 colony forming units (cfu)/mL level with excellent discrimination against any other bacteria. TPRS intensity increases 40 times when anti- E. coli antibody-conjugated nanorods were mixed with various concentrations of Escherichia coli O157:H7 bacterium. The mechanism of TPRS intensity change has been discussed. This bionanotechnology assay could be adapted in studies using antibodies specific for various bacterial pathogens for the detection of a wide variety of bacterial pathogens used as bioterrorism agents in food, clinical samples, and environmental samples.
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Affiliation(s)
- Anant K. Singh
- Department of Chemistry, Jackson State University, Jackson, MS, USA
| | - Dulal Senapati
- Department of Chemistry, Jackson State University, Jackson, MS, USA
| | - Shuguang Wang
- Department of Chemistry, Jackson State University, Jackson, MS, USA
| | - Jelani Griffin
- Department of Chemistry, Jackson State University, Jackson, MS, USA
| | - Adria Neely
- Department of Chemistry, Jackson State University, Jackson, MS, USA
| | - Perry Candice
- Department of Chemistry, Jackson State University, Jackson, MS, USA
| | | | - Birsen Varisli
- Department of Chemistry, Jackson State University, Jackson, MS, USA
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Best A, Clifford D, Crudgington B, Cooley WA, Nunez A, Carter B, Weyer U, Woodward MJ, La Ragione RM. Intermittent Escherichia coli O157:H7 colonisation at the terminal rectum mucosa of conventionally-reared lambs. Vet Res 2008; 40:9. [PMID: 18959839 PMCID: PMC2695016 DOI: 10.1051/vetres:2008047] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2008] [Accepted: 10/28/2008] [Indexed: 12/24/2022] Open
Abstract
In cattle, the lymphoid rich regions of the rectal-anal mucosa at the terminal rectum are the preferred site for Escherichia coli O157:H7 colonisation. All cattle infected by rectal swab administration demonstrate long-term E. coli O157:H7 colonisation, whereas orally challenged cattle do not demonstrate long-term E. coli O157:H7 colonisation in all animals. Oral, but not rectal challenge of sheep with E. coli O157:H7 has been reported, but an exact site for colonisation in sheep is unknown. To determine if E. coli O157:H7 can effectively colonise the ovine terminal rectum, in vitro organ culture (IVOC) was initiated. Albeit sparsely, large, densely packed E. coli O157:H7 micro-colonies were observed on the mucosa of ovine and control bovine terminal rectum explants. After necropsy of orally inoculated lambs, bacterial enumeration of the proximal and distal gastrointestinal tract did suggest a preference for E. coli O157:H7 colonisation at the ovine terminal rectum, albeit for both lymphoid rich and non-lymphoid sites. As reported for cattle, rectal inoculation studies were then conducted to determine if all lambs would demonstrate persistent colonisation at the terminal rectum. After necropsy of E. coli O157:H7 rectally inoculated lambs, most animals were not colonised at gastrointestinal sites proximal to the rectum, however, large densely packed micro-colonies of E. coli O157:H7 were observed on the ovine terminal rectum mucosa. Nevertheless, at the end point of the study (day 14), only one lamb had E. coli O157:H7 micro-colonies associated with the terminal rectum mucosa. A comparison of E. coli O157:H7 shedding yielded a similar pattern of persistence between rectally and orally inoculated lambs. The inability of E. coli O157:H7 to effectively colonise the terminal rectum mucosa of all rectally inoculated sheep in the long term, suggests that E. coli O157:H7 may colonise this site, but less effectively than reported previously for cattle.
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Affiliation(s)
- Angus Best
- Department of Food and Environmental Safety, Veterinary Laboratories Agency (VLA), Weybridge, Woodham Lane, New Haw, Addlestone, Surrey, KT15 3NB, United Kingdom.
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Soni K, Lu L, Jesudhasan P, Hume M, Pillai S. Influence of Autoinducer-2 (AI-2) and Beef Sample Extracts on E. coli O157:H7 Survival and Gene Expression of Virulence Genes yadK and hhA. J Food Sci 2008; 73:M135-9. [DOI: 10.1111/j.1750-3841.2007.00654.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Detection of viable but nonculturable Escherichia coli O157:H7 bacteria in drinking water and river water. Appl Environ Microbiol 2008; 74:1502-7. [PMID: 18203853 DOI: 10.1128/aem.02125-07] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A sensitive method for specific detection of viable Escherichia coli O157:H7 cells, including viable but nonculturable (VBNC) cells, in water samples was developed. This method involved capture of the bacterial cells on a low-protein-binding membrane and direct extraction and purification of RNA followed by reverse transcription-PCR and electronic microarray detection of the rfbE and fliC genes of E. coli O157:H7. It detected as few as 1 CFU of E. coli O157:H7 in diluted cultures, 3 to 4 CFU/liter in tap water, 7 CFU/liter in river water, and 50 VBNC cells in 1 liter of river water, demonstrating the best limit of detection reported to date for VBNC cells in environmental water samples.
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