101
|
Amani J, Mousavi SL, Rafati S, Salmanian AH. Immunogenicity of a plant-derived edible chimeric EspA, Intimin and Tir of Escherichia coli O157:H7 in mice. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2011; 180:620-7. [PMID: 21421410 DOI: 10.1016/j.plantsci.2011.01.004] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2010] [Revised: 12/26/2010] [Accepted: 01/05/2011] [Indexed: 05/30/2023]
Abstract
Transgenic plants offer the possibility to produce and deliver an oral immunogen on a large-scale with low production costs and minimal purification or enrichment. Cattles are important reservoirs of Escherichia coli O157:H7 and developing a specific immunity in animals would be invaluable. Intimin, Tir, and EspA proteins are the virulence factors expressed by LEE locus of enterohemorrhagic E. coli. We hypothesized that the chimeric recombinant forms of these effectors delivered as an edible-base vaccine would reduce colonization of bacteria in mice. A synthetic gene (eit) composed of espA (e), eae (i) and tir (t) attached by linkers was constructed. The gene was codon optimized and cloned into plant expression vectors adjacent to CaMV35S and FAE promoters for expression in tobacco and canola plants. Of total soluble protein 0.2% and 0.3% (in average) were detected in transgenic tobacco leaves and canola seeds respectively. Mice immunized either subcutaneously or orally with recombinant EIT and challenged with E. coli O157:H7 significantly exhibited reduced bacterial shedding. Application of transgenic plants containing trivalent immunogen is an effective tool for protection against E. coli O157:H7.
Collapse
MESH Headings
- Adhesins, Bacterial/genetics
- Adhesins, Bacterial/immunology
- Animals
- Brassica napus/genetics
- Cloning, Molecular
- Enzyme-Linked Immunosorbent Assay
- Escherichia coli O157/genetics
- Escherichia coli O157/immunology
- Escherichia coli O157/pathogenicity
- Escherichia coli Proteins/genetics
- Escherichia coli Proteins/immunology
- Female
- Immunity, Humoral
- Immunity, Mucosal
- Immunization/methods
- Mice
- Mice, Inbred BALB C
- Plants, Genetically Modified/metabolism
- Receptors, Cell Surface/genetics
- Receptors, Cell Surface/immunology
- Recombinant Fusion Proteins/immunology
- Nicotiana/genetics
- Transformation, Genetic
Collapse
Affiliation(s)
- Jafar Amani
- Department of Plant Biotechnology, National Institute of Genetic Engineering and Biotechnology (NIGEB), Tehran, Iran
| | | | | | | |
Collapse
|
102
|
Yekta MA, Cox E, Goddeeris BM, Vanrompay D. Reduction of Escherichia coli O157:H7 excretion in sheep by oral lactoferrin administration. Vet Microbiol 2011; 150:373-8. [PMID: 21511407 DOI: 10.1016/j.vetmic.2011.02.052] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2010] [Revised: 02/21/2011] [Accepted: 02/24/2011] [Indexed: 12/14/2022]
Abstract
Ruminants are an important reservoir of Escherichia coli O157:H7, therefore reducing E. coli O157:H7 excretion by these animals could play a key role in reducing human infections. The present study investigates the potential of bovine lactoferrin, a natural antimicrobial-immunomodulatory protein of milk, to prevent colonization and excretion of E. coli O157:H7 in sheep. The effect of two different doses of lactoferrin (1.5 g or 0.15 g per 12h) was evaluated on colonization of sheep intestine and faecal excretion of the NCTC12900 strain. Hereto, lactoferrin was orally administered to sheep during 30 consecutive days and sheep were experimentally infected with E. coli O157:H7 on the second day of the lactoferrin administration. Interestingly, both lactoferrin dosages significantly reduced the number of E. coli O157:H7 in faeces as well as the duration of faecal excretion. The high dose group showed a significantly higher antibody response against EspA and EspB, two structural proteins of the bacterial type III secretion system (TTSS), than the colonization control group. The results suggest that oral lactoferrin administration could be used to prevent persistent colonization of sheep with E. coli O157:H7.
Collapse
Affiliation(s)
- M Atef Yekta
- Laboratory of Immunology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, B-9820 Merelbeke, Belgium.
| | | | | | | |
Collapse
|
103
|
Immunization of sheep with a combination of intiminγ, EspA and EspB decreases Escherichia coli O157:H7 shedding. Vet Immunol Immunopathol 2011; 140:42-6. [DOI: 10.1016/j.vetimm.2010.11.010] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2010] [Revised: 11/07/2010] [Accepted: 11/11/2010] [Indexed: 12/22/2022]
|
104
|
Reduction of Escherichia coli O157:H7 shedding in cattle by addition of chitosan microparticles to feed. Appl Environ Microbiol 2011; 77:2611-6. [PMID: 21335379 DOI: 10.1128/aem.02587-10] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Enterohemorrhagic Escherichia coli O157:H7 (EHEC) is a significant human pathogen that resides in healthy cattle. It is thought that a reduction in the prevalence and numbers of EHEC in cattle will reduce the load of EHEC entering the food chain. To this end, an intervention strategy involving the addition of chitosan microparticles (CM) to feed in order to reduce the carriage of this pathogen in cattle was evaluated. Experiments with individual Holstein calves and a crossover study found that the addition of CM to feed decreased E. coli O157:H7 shedding. In the crossover study, CM resulted in statistically significant reductions in the numbers recovered from rectal swab samples (P < 0.05) and the duration of shedding (P < 0.05). The effects of feeding CM to calves differed, indicating that the optimal levels of CM may differ between animals or that other factors are involved in the interaction between CM and E. coli O157:H7. In vitro studies demonstrated that E. coli O157:H7 binds to CM, suggesting that the reduction in shedding may result at least in part from the binding of positively charged CM to negatively charged E. coli cells. Additional studies are needed to determine the impact of CM feeding on animal production, but the results from this study indicate that supplementing feed with CM reduces the shedding of E. coli O157:H7 in cattle.
Collapse
|
105
|
Zhang XS, Woolhouse MEJ. Escherichia coli O157 infection on Scottish cattle farms: dynamics and control. J R Soc Interface 2010; 8:1051-8. [PMID: 21084345 PMCID: PMC3104328 DOI: 10.1098/rsif.2010.0470] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
In this study, we parametrize a stochastic individual-based model of the transmission dynamics of Escherichia coli O157 infection among Scottish cattle farms and use the model to predict the impacts of both targeted and non-targeted interventions. We first generate distributions of model parameter estimates using Markov chain Monte Carlo methods. Despite considerable uncertainty in parameter values, each set of parameter values within the 95th percentile range implies a fairly similar impact of interventions. Interventions that reduce the transmission coefficient and/or increase the recovery rate of infected farms (e.g. via vaccination and biosecurity) are much more effective in reducing the level of infection than reducing cattle movement rates, which improves effectiveness only when the overall control effort is small. Targeted interventions based on farm-level risk factors are more efficient than non-targeted interventions. Herd size is a major determinant of risk of infection, and our simulations confirmed that targeting interventions at farms with the largest herds is almost as effective as targeting based on overall risk. However, because of the striking characteristic that the infection force depends weakly on the number of infected farms, no interventions that are less than 100 per cent effective can eradicate E. coli O157 infection from Scottish cattle farms, implying that eliminating the disease is impractical.
Collapse
Affiliation(s)
- Xu-Sheng Zhang
- Centre for Infectious Diseases, University of Edinburgh, , Kings Buildings, West Mains Road, Edinburgh EH9 3JT, UK.
| | | |
Collapse
|
106
|
Immunogenic properties of chimeric protein from espA, eae and tir genes of Escherichia coli O157:H7. Vaccine 2010; 28:6923-9. [DOI: 10.1016/j.vaccine.2010.07.061] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2010] [Revised: 07/16/2010] [Accepted: 07/19/2010] [Indexed: 01/18/2023]
|
107
|
Misyurina O, Asper DJ, Deng W, Finlay BB, Rogan D, Potter AA. The role of Tir, EspA, and NleB in the colonization of cattle by Shiga toxin producingEscherichia coliO26:H11. Can J Microbiol 2010; 56:739-47. [DOI: 10.1139/w10-059] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Shiga toxin producing Escherichia coli (STEC) O26:H11 is an enteric pathogen capable of causing severe hemorrhagic colitis that can lead to hemolytic uremic syndrome. This organism is able to colonize cattle and human intestinal epithelial cells by secreting effectors via a type III secretion system (T3SS). In this investigation, we examined the role of 2 effectors, Tir and NleB, and the structural translocator component EspA in the adherence of STEC to epithelial cells and in the colonization of cattle. Isogenic deletion mutants were constructed and using microscopy and flow cytometry compared to the wild-type strain in their ability to adhere to HEp-2 cells. A competitive assay was also used to measure the capacity of the mutants to colonize the intestinal tract of cattle, where both the mutant and the parental strains were introduced orally at the same time. Genomic DNA was extracted from enriched fecal samples collected at various time points, and quantitative real-time PCR was used to quantify bacteria. A significant reduction in fecal shedding was observed, and adherence to HEp-2 cells was decreased for the tir and espA mutants. Deletion of the nleB gene did not have a significant effect on the adherence of HEp-2 cells; however, in an in vivo model, it strongly reduced the ability of STEC O26:H11 to colonize the bovine intestinal tract.
Collapse
Affiliation(s)
- Olga Misyurina
- Vaccine and Infectious Disease Organization, University of Saskatchewan, 120 Veterinary Road, Saskatoon, SK S7N 5E3, Canada
- Michael Smith Laboratories, University of British Columbia, 2185 East Mall, Vancouver, BC V6T 1Z4, Canada
- Bioniche Life Sciences, 231 Dundas Street East, Belleville, ON K8N 1E2, Canada
| | - David J. Asper
- Vaccine and Infectious Disease Organization, University of Saskatchewan, 120 Veterinary Road, Saskatoon, SK S7N 5E3, Canada
- Michael Smith Laboratories, University of British Columbia, 2185 East Mall, Vancouver, BC V6T 1Z4, Canada
- Bioniche Life Sciences, 231 Dundas Street East, Belleville, ON K8N 1E2, Canada
| | - Wanyin Deng
- Vaccine and Infectious Disease Organization, University of Saskatchewan, 120 Veterinary Road, Saskatoon, SK S7N 5E3, Canada
- Michael Smith Laboratories, University of British Columbia, 2185 East Mall, Vancouver, BC V6T 1Z4, Canada
- Bioniche Life Sciences, 231 Dundas Street East, Belleville, ON K8N 1E2, Canada
| | - B. Brett Finlay
- Vaccine and Infectious Disease Organization, University of Saskatchewan, 120 Veterinary Road, Saskatoon, SK S7N 5E3, Canada
- Michael Smith Laboratories, University of British Columbia, 2185 East Mall, Vancouver, BC V6T 1Z4, Canada
- Bioniche Life Sciences, 231 Dundas Street East, Belleville, ON K8N 1E2, Canada
| | - Dragan Rogan
- Vaccine and Infectious Disease Organization, University of Saskatchewan, 120 Veterinary Road, Saskatoon, SK S7N 5E3, Canada
- Michael Smith Laboratories, University of British Columbia, 2185 East Mall, Vancouver, BC V6T 1Z4, Canada
- Bioniche Life Sciences, 231 Dundas Street East, Belleville, ON K8N 1E2, Canada
| | - Andrew A. Potter
- Vaccine and Infectious Disease Organization, University of Saskatchewan, 120 Veterinary Road, Saskatoon, SK S7N 5E3, Canada
- Michael Smith Laboratories, University of British Columbia, 2185 East Mall, Vancouver, BC V6T 1Z4, Canada
- Bioniche Life Sciences, 231 Dundas Street East, Belleville, ON K8N 1E2, Canada
| |
Collapse
|
108
|
Vande Walle K, Yekta MA, Verdonck F, De Zutter L, Cox E. Rectal inoculation of sheep with E. coli O157:H7 results in persistent infection in the absence of a protective immune response. Vet Microbiol 2010; 147:376-82. [PMID: 20675082 DOI: 10.1016/j.vetmic.2010.06.033] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2010] [Revised: 06/07/2010] [Accepted: 06/29/2010] [Indexed: 11/16/2022]
Abstract
Escherichia coli (E. coli) O157:H7 can cause haemorrhagic colitis and the haemolytic uremic syndrome in humans. Ruminants are the main reservoir for this bacterium: they can harbour the bacteria in the gastrointestinal tract without showing clinical symptoms. The reason for this persistence is still unclear, although it has been suggested that E. coli O157:H7 can suppress the immune system. To investigate the effects on the immune system of ruminants, an infection model is needed that mimics a long-term infection as it can occur in both sheep and cattle. As the terminal rectum has recently been identified as a primary colonisation site in cattle, we developed a rectal inoculation model for sheep and used this model to study immune responses against selected virulence factors of E. coli O157:H7 (intimin, EspA and EspB). Sheep were infected and re-infected when E. coli O157:H7 excretion was no longer detectable. The animals did not develop serum or local antibody responses but showed a cellular response against EspA and intimin respectively 9 and 16 days after infection. This response was also present 5 days after re-infection, albeit lower, and did not prevent animals from being re-infected. These results demonstrate that E. coli O157:H7 can be persistently present in the large intestine of sheep without inducing a clear protective immune response.
Collapse
Affiliation(s)
- Kris Vande Walle
- Laboratory of Immunology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium.
| | | | | | | | | |
Collapse
|
109
|
Cai K, Gao X, Li T, Hou X, Wang Q, Liu H, Xiao L, Tu W, Liu Y, Shi J, Wang H. Intragastric immunization of mice with enterohemorrhagicEscherichia coliO157:H7 bacterial ghosts reduces mortality and shedding and induces a Th2-type dominated mixed immune response. Can J Microbiol 2010; 56:389-98. [DOI: 10.1139/w10-025] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A bacterial ghost (BG)-based vaccine was developed against enterohemorrhagic Escherichia coli O157:H7 infection. The aim of this study was to evaluate the protective effect of E. coli O157:H7 BGs in a mouse model and to reveal the mechanism of the immune response. Booster immunization provided a higher protection rate (84%) than single-dose immunization (56%). Intragastric immunization of E. coli O157:H7 BGs induced both humoral and cellular immune responses. The proliferative response of CD4+T cells was mediated by the antigen-presenting cells. The humoral immune response dominated the immune response, while the cellular immune response developed later. Inflammatory reaction was balanced by the mixed Th1/Th2 immune response. The immune sera anti-adhesion effect was confirmed by the inhibition effect, which could inhibit >90% of the adhesion of E. coli O157:H7 to Hep-2 target cells in vitro. Antibody titer specific for intimin, a molecule important for adhesion of E. coli O157:H7 to target cells, correlated with specific immunoglobulin A or G antibody titer. Therefore, it might be feasible to clinically test BG vaccines in the future.
Collapse
Affiliation(s)
- Kun Cai
- State Key Laboratory of Pathogens and Biosecurity, Beijing Institute of Microbiology and Epidemiology, No. 20 Dongdajie, Fengtai District, Beijing 100071, P.R. China
| | - Xiang Gao
- State Key Laboratory of Pathogens and Biosecurity, Beijing Institute of Microbiology and Epidemiology, No. 20 Dongdajie, Fengtai District, Beijing 100071, P.R. China
| | - Tao Li
- State Key Laboratory of Pathogens and Biosecurity, Beijing Institute of Microbiology and Epidemiology, No. 20 Dongdajie, Fengtai District, Beijing 100071, P.R. China
| | - Xiaojun Hou
- State Key Laboratory of Pathogens and Biosecurity, Beijing Institute of Microbiology and Epidemiology, No. 20 Dongdajie, Fengtai District, Beijing 100071, P.R. China
| | - Qin Wang
- State Key Laboratory of Pathogens and Biosecurity, Beijing Institute of Microbiology and Epidemiology, No. 20 Dongdajie, Fengtai District, Beijing 100071, P.R. China
| | - Hao Liu
- State Key Laboratory of Pathogens and Biosecurity, Beijing Institute of Microbiology and Epidemiology, No. 20 Dongdajie, Fengtai District, Beijing 100071, P.R. China
| | - Le Xiao
- State Key Laboratory of Pathogens and Biosecurity, Beijing Institute of Microbiology and Epidemiology, No. 20 Dongdajie, Fengtai District, Beijing 100071, P.R. China
| | - Wei Tu
- State Key Laboratory of Pathogens and Biosecurity, Beijing Institute of Microbiology and Epidemiology, No. 20 Dongdajie, Fengtai District, Beijing 100071, P.R. China
| | - Yuenan Liu
- State Key Laboratory of Pathogens and Biosecurity, Beijing Institute of Microbiology and Epidemiology, No. 20 Dongdajie, Fengtai District, Beijing 100071, P.R. China
| | - Jing Shi
- State Key Laboratory of Pathogens and Biosecurity, Beijing Institute of Microbiology and Epidemiology, No. 20 Dongdajie, Fengtai District, Beijing 100071, P.R. China
| | - Hui Wang
- State Key Laboratory of Pathogens and Biosecurity, Beijing Institute of Microbiology and Epidemiology, No. 20 Dongdajie, Fengtai District, Beijing 100071, P.R. China
| |
Collapse
|
110
|
Interventions to reduce verocytotoxigenic Escherichia coli in ground beef in Argentina: A simulation study. Prev Vet Med 2010; 94:36-42. [DOI: 10.1016/j.prevetmed.2009.11.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2009] [Revised: 11/09/2009] [Accepted: 11/17/2009] [Indexed: 11/30/2022]
|
111
|
Estes DM, Dow SW, Schweizer HP, Torres AG. Present and future therapeutic strategies for melioidosis and glanders. Expert Rev Anti Infect Ther 2010; 8:325-38. [PMID: 20192686 PMCID: PMC2856610 DOI: 10.1586/eri.10.4] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Burkholderia pseudomallei and Burkholderia mallei are the causative agents of melioidosis and glanders, respectively. Both Gram-negative pathogens are endemic in many parts of the world. Although natural acquisition of these pathogens is rare in the majority of countries, these bacteria have recently gained much interest because of their potential as bioterrorism agents. In modern times, their potential destructive impact on public health has escalated owing to the ability of these pathogens to cause opportunistic infections in diabetic and perhaps otherwise immunocompromised people, two growing populations worldwide. For both pathogens, severe infection in humans carries a high mortality rate, both species are recalcitrant to antibiotic therapy - B. pseudomallei more so than B. mallei - and no licensed vaccine exists for either prophylactic or therapeutic use. The potential malicious use of these organisms has accelerated the investigation of new ways to prevent and to treat the diseases. The availability of several B. pseudomallei and B. mallei genome sequences has greatly facilitated target identification and development of new therapeutics. This review provides a compilation of literature covering studies in antimelioidosis and antiglanders antimicrobial drug discovery, with a particular focus on potential novel therapeutic approaches to combat these diseases.
Collapse
Affiliation(s)
- D Mark Estes
- Department of Microbiology and Immunology, Department of Pathology and The Sealy Center for Vaccine Development, University of Texas Medical Branch, Galveston, TX 77555-1070, USA, Tel.: +1 409 266 6523, Fax: +1 409 266 6810,
| | - Steven W Dow
- Department of Microbiology, Immunology and Pathology, Colorado State University, College of Veterinary Medicine and Biomedical Science, Fort Collins, CO 80523, USA,
| | - Herbert P Schweizer
- Department of Microbiology, Immunology and Pathology, Colorado State University, College of Veterinary Medicine and Biomedical Science, Fort Collins, CO 80523, USA,
| | - Alfredo G Torres
- Department of Microbiology and Immunology, Department of Pathology and The Sealy Center for Vaccine Development, University of Texas Medical Branch, Galveston, TX 77555-1070, USA,
| |
Collapse
|
112
|
Salmonella enterica serovar Typhimurium vaccine strains expressing a nontoxic Shiga-like toxin 2 derivative induce partial protective immunity to the toxin expressed by enterohemorrhagic Escherichia coli. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2010; 17:529-36. [PMID: 20147499 DOI: 10.1128/cvi.00495-09] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Shiga-like toxin 2 (Stx2)-producing enterohemorrhagic Escherichia coli (referred to as EHEC or STEC) strains are the primary etiologic agents of hemolytic-uremic syndrome (HUS), which leads to renal failure and high mortality rates. Expression of Stx2 is the most relevant virulence-associated factor of EHEC strains, and toxin neutralization by antigen-specific serum antibodies represents the main target for both preventive and therapeutic anti-HUS approaches. In the present report, we describe two Salmonella enterica serovar Typhimurium aroA vaccine strains expressing a nontoxic plasmid-encoded derivative of Stx2 (Stx2DeltaAB) containing the complete nontoxic A2 subunit and the receptor binding B subunit. The two S. Typhimurium strains differ in the expression of flagellin, the structural subunit of the flagellar shaft, which exerts strong adjuvant effects. The vaccine strains expressed Stx2DeltaAB, either cell bound or secreted into the extracellular environment, and showed enhanced mouse gut colonization and high plasmid stability under both in vitro and in vivo conditions. Oral immunization of mice with three doses of the S. Typhimurium vaccine strains elicited serum anti-Stx2B (IgG) antibodies that neutralized the toxic effects of the native toxin under in vitro conditions (Vero cells) and conferred partial protection under in vivo conditions. No significant differences with respect to gut colonization or the induction of antigen-specific antibody responses were detected in mice vaccinated with flagellated versus nonflagellated bacterial strains. The present results indicate that expression of Stx2DeltaAB by attenuated S. Typhimurium strains is an alternative vaccine approach for HUS control, but additional improvements in the immunogenicity of Stx2 toxoids are still required.
Collapse
|
113
|
Berry ED, Wells JE. Escherichia coli O157:H7: recent advances in research on occurrence, transmission, and control in cattle and the production environment. ADVANCES IN FOOD AND NUTRITION RESEARCH 2010; 60:67-117. [PMID: 20691954 DOI: 10.1016/s1043-4526(10)60004-6] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Escherichia coli O157:H7 is a zoonotic pathogen that is an important cause of human foodborne and waterborne disease, with a spectrum of illnesses ranging from asymptomatic carriage and diarrhea to the sometimes fatal hemolytic uremic syndrome. Outbreaks of E. coli O157:H7 disease are often associated with undercooked beef, but there are other sources of transmission, including water, produce, and animal contact, which can often be linked directly or indirectly to cattle. Thus, preharvest control of this pathogen in cattle production should have a large impact on reducing the risk of human foodborne illness. In this review, we will summarize preharvest research on E. coli O157:H7 in cattle and the production environment, focusing on factors that may influence the transmission, prevalence, and levels of this pathogen, such as season, diet, high-level shedders, and animal stress. In addition, we will discuss recent research on the reduction of this pathogen in cattle production, including vaccination, probiotics, bacteriophage, and manure treatments.
Collapse
Affiliation(s)
- Elaine D Berry
- U.S. Department of Agriculture, Agricultural Research Service, U.S. Meat Animal Research Center, Clay Center, Nebraska, USA.
| | | |
Collapse
|
114
|
Karmali MA, Gannon V, Sargeant JM. Verocytotoxin-producing Escherichia coli (VTEC). Vet Microbiol 2010; 140:360-70. [DOI: 10.1016/j.vetmic.2009.04.011] [Citation(s) in RCA: 352] [Impact Index Per Article: 25.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2009] [Revised: 03/27/2009] [Accepted: 04/03/2009] [Indexed: 01/10/2023]
|
115
|
Abstract
BACKGROUND The quantification of uncertainty and variability is a key component of quantitative risk analysis. Recent advances in Bayesian statistics make it ideal for integrating multiple sources of information, of different types and quality, and providing a realistic estimate of the combined uncertainty in the final risk estimates. METHODS We present two case studies related to foodborne microbial risks. In the first, we combine models to describe the sequence of events resulting in illness from consumption of milk contaminated with VTEC O157. We used Monte Carlo simulation to propagate uncertainty in some of the inputs to computer models describing the farm and pasteurisation process. Resulting simulated contamination levels were then assigned to consumption events from a dietary survey. Finally we accounted for uncertainty in the dose-response relationship and uncertainty due to limited incidence data to derive uncertainty about yearly incidences of illness in young children. Options for altering the risk were considered by running the model with different hypothetical policy-driven exposure scenarios. In the second case study we illustrate an efficient Bayesian sensitivity analysis for identifying the most important parameters of a complex computer code that simulated VTEC O157 prevalence within a managed dairy herd. This was carried out in 2 stages, first to screen out the unimportant inputs, then to perform a more detailed analysis on the remaining inputs. The method works by building a Bayesian statistical approximation to the computer code using a number of known code input/output pairs (training runs). RESULTS We estimated that the expected total number of children aged 1.5-4.5 who become ill due to VTEC O157 in milk is 8.6 per year, with 95% uncertainty interval (0,11.5). The most extreme policy we considered was banning on-farm pasteurisation of milk, which reduced the estimate to 6.4 with 95% interval (0,11). In the second case study the effective number of inputs was reduced from 30 to 7 in the screening stage, and just 2 inputs were found to explain 82.8% of the output variance. A combined total of 500 runs of the computer code were used. CONCLUSION These case studies illustrate the use of Bayesian statistics to perform detailed uncertainty and sensitivity analyses, integrating multiple information sources in a way that is both rigorous and efficient.
Collapse
Affiliation(s)
- Marc C Kennedy
- Food and Environment Research Agency, Sand Hutton, York, YO41 1LZ, UK
| | - Helen E Clough
- National Centre for Zoonosis Research, University of Liverpool, Leahurst, Neston, South Wirral, CH64 7TE, UK
| | - Joanne Turner
- Department of Veterinary Clinical Science, University of Liverpool, Leahurst, Neston, South Wirral, CH64 7TE, UK
| |
Collapse
|
116
|
In silico analysis of chimeric espA, eae and tir fragments of Escherichia coli O157:H7 for oral immunogenic applications. Theor Biol Med Model 2009; 6:28. [PMID: 19995413 PMCID: PMC3224939 DOI: 10.1186/1742-4682-6-28] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2009] [Accepted: 12/08/2009] [Indexed: 01/23/2023] Open
Abstract
Background In silico techniques are highly suited for both the discovery of new and development of existing vaccines. Enterohemorrhagic Escherichia coli O157:H7 (EHEC) exhibits a pattern of localized adherence to host cells, with the formation of microcolonies, and induces a specific histopathological lesion (attaching/effacing). The genes encoding the products responsible for this phenotype are clustered on a 35-kb pathogenicity island. Among these proteins, Intimin, Tir, and EspA, which are expressed by attaching-effacing genes, are responsible for the attachment to epithelial cell that leads to lesions. Results We designed synthetic genes encoding the carboxy-terminal fragment of Intimin, the middle region of Tir and the carboxy-terminal part of EspA. These multi genes were synthesized with codon optimization for a plant host and were fused together by the application of four repeats of five hydrophobic amino acids as linkers. The structure of the synthetic construct gene, its mRNA and deduced protein and their stabilities were analyzed by bioinformatic software. Furthermore, the immunogenicity of this multimeric recombinant protein consisting of three different domains was predicted. Conclusion a structural model for a chimeric gene from LEE antigenic determinants of EHEC is presented. It may define accessibility, solubility and immunogenecity.
Collapse
|
117
|
McNeilly TN, Mitchell MC, Rosser T, McAteer S, Low JC, Smith DGE, Huntley JF, Mahajan A, Gally DL. Immunization of cattle with a combination of purified intimin-531, EspA and Tir significantly reduces shedding of Escherichia coli O157:H7 following oral challenge. Vaccine 2009; 28:1422-8. [PMID: 19903545 DOI: 10.1016/j.vaccine.2009.10.076] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2009] [Revised: 09/28/2009] [Accepted: 10/14/2009] [Indexed: 01/06/2023]
Abstract
Enterohemorrhagic Escherichia coli (EHEC) O157:H7 is a human pathogen that can cause gastrointestinal disease with potentially fatal consequences as a result of systemic Shiga toxin activity. Cattle are the main reservoir host of EHEC O157 and interventions need to be developed that prevent cattle colonization or limit shedding of the organism from this host. EHEC O157 predominately colonizes the bovine terminal rectum and requires a type III secretion system (T3SS) for adherence and persistence at this site. A vaccine based on concentrated bacterial supernatant that contains T3S proteins has shown some efficacy. Here we have demonstrated that vaccination with a combination of antigens associated with T3S-mediated adherence; the translocon filament protein, EspA, the extracellular region of the outer membrane adhesin, intimin, and the translocated intimin receptor (Tir) significantly reduced shedding of EHEC O157 from experimentally infected animals. Furthermore, this protection may be augmented by addition of H7 flagellin to the vaccine preparation that has been previously demonstrated to be partially protective in cattle. Protection correlates with systemic and mucosal antibody responses to the defined antigens and validates the targeting of these colonization factors.
Collapse
Affiliation(s)
- Tom N McNeilly
- Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik, EH26 0PZ, UK
| | | | | | | | | | | | | | | | | |
Collapse
|
118
|
Fox JT, Thomson DU, Drouillard JS, Thornton AB, Burkhardt DT, Emery DA, Nagaraja T. Efficacy ofEscherichia coliO157:H7 Siderophore Receptor/Porin Proteins–Based Vaccine in Feedlot Cattle Naturally SheddingE. coliO157. Foodborne Pathog Dis 2009; 6:893-9. [DOI: 10.1089/fpd.2009.0336] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- J. Trent Fox
- Department of Diagnostic Medicine/Pathobiology, Kansas State University, Manhattan, Kansas
| | - Daniel U. Thomson
- Department of Clinical Sciences, Kansas State University, Manhattan, Kansas
| | - James S. Drouillard
- Department of Animal Sciences and Industry, Kansas State University, Manhattan, Kansas
| | - Ashley B. Thornton
- Department of Diagnostic Medicine/Pathobiology, Kansas State University, Manhattan, Kansas
| | | | | | - T.G. Nagaraja
- Department of Diagnostic Medicine/Pathobiology, Kansas State University, Manhattan, Kansas
| |
Collapse
|
119
|
|
120
|
Smith DR, Moxley RA, Klopfenstein TJ, Erickson GE. A Randomized Longitudinal Trial to Test the Effect of Regional Vaccination Within a Cattle Feedyard on Escherichia coli O157:H7 Rectal Colonization, Fecal Shedding, and Hide Contamination. Foodborne Pathog Dis 2009; 6:885-92. [DOI: 10.1089/fpd.2009.0299] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- David R. Smith
- Department of Veterinary and Biomedical Sciences, University of Nebraska–Lincoln, Lincoln, Nebraska
| | - Rodney A. Moxley
- Department of Veterinary and Biomedical Sciences, University of Nebraska–Lincoln, Lincoln, Nebraska
| | | | - Galen E. Erickson
- Department of Animal Science, University of Nebraska–Lincoln, Lincoln, Nebraska
| |
Collapse
|
121
|
Gu J, Liu Y, Yu S, Wang H, Wang Q, Yi Y, Zhu F, Yu XJ, Zou Q, Mao X. Enterohemorrhagic Escherichia coli trivalent recombinant vaccine containing EspA, intimin and Stx2 induces strong humoral immune response and confers protection in mice. Microbes Infect 2009; 11:835-41. [DOI: 10.1016/j.micinf.2009.04.024] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2009] [Revised: 04/22/2009] [Accepted: 04/23/2009] [Indexed: 11/27/2022]
|
122
|
Thomson DU, Loneragan GH, Thornton AB, Lechtenberg KF, Emery DA, Burkhardt DT, Nagaraja TG. Use of a Siderophore Receptor and Porin Proteins-Based Vaccine to Control the Burden ofEscherichia coliO157:H7 in Feedlot Cattle. Foodborne Pathog Dis 2009; 6:871-7. [DOI: 10.1089/fpd.2009.0290] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Daniel U. Thomson
- Department of Clinical Sciences, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas
| | - Guy H. Loneragan
- Department of Agricultural Sciences, West Texas A&M University, Canyon, Texas
| | - Ashley B. Thornton
- Department of Clinical Sciences, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas
| | | | | | | | - Triuvoor G. Nagaraja
- Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas
| |
Collapse
|
123
|
Kim HN, Hong Y, Lee I, Bradford SA, Walker SL. Surface Characteristics and Adhesion Behavior of Escherichia coli O157:H7: Role of Extracellular Macromolecules. Biomacromolecules 2009; 10:2556-64. [DOI: 10.1021/bm900516y] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Hyunjung N. Kim
- Department of Chemical and Environmental Engineering, and Department of Chemistry, University of California, Riverside, California 92521, and USDA, ARS, US Salinity Laboratory, Riverside, California 92507
| | - Yongsuk Hong
- Department of Chemical and Environmental Engineering, and Department of Chemistry, University of California, Riverside, California 92521, and USDA, ARS, US Salinity Laboratory, Riverside, California 92507
| | - Ilkeun Lee
- Department of Chemical and Environmental Engineering, and Department of Chemistry, University of California, Riverside, California 92521, and USDA, ARS, US Salinity Laboratory, Riverside, California 92507
| | - Scott A. Bradford
- Department of Chemical and Environmental Engineering, and Department of Chemistry, University of California, Riverside, California 92521, and USDA, ARS, US Salinity Laboratory, Riverside, California 92507
| | - Sharon L. Walker
- Department of Chemical and Environmental Engineering, and Department of Chemistry, University of California, Riverside, California 92521, and USDA, ARS, US Salinity Laboratory, Riverside, California 92507
| |
Collapse
|
124
|
Smith DR, Moxley RA, Peterson RE, Klopfenstein TJ, Erickson GE, Bretschneider G, Berberov EM, Clowser S. A two-dose regimen of a vaccine against type III secreted proteins reduced Escherichia coli O157:H7 colonization of the terminal rectum in beef cattle in commercial feedlots. Foodborne Pathog Dis 2009; 6:155-61. [PMID: 19105625 DOI: 10.1089/fpd.2008.0136] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
A large-scale clinical vaccine trial of commercially fed cattle was conducted to test the efficacy of a two-dose regimen of a vaccine product against type III secreted proteins of enterohemorrhagic Escherichia coli O157:H7 on the probability to detect the same organism from terminal rectal mucosa (TRM) as a measure of gut colonization. Vaccine was administered to all cattle within treated pens at arrival processing and at reimplant processing. At harvest, TRM was collected from a sample of cattle from within vaccinated and nonvaccinated pens. The TRM were collected by scraping the mucosa of the terminal rectum 3-5 cm proximal to the rectoanal juncture. E. coli O157:H7 was isolated and identified from TRM using standard culture methods involving selective enrichment, immunomagnetic separation, and PCR confirmation. The probability to detect E. coli O157:H7 from TRM was modeled using a generalized linear mixed model with a logit link function and accounting for random effects of pen within feedlot. Seven hundred eighteen cattle were tested from within 21 pens of cattle (11 vaccinated and 10 not vaccinated) representing 3683 cattle. E. coli O157:H7 was cultured from 68 of 718 (9.5%) TRM samples. Eleven of 382 (2.9%) vaccinated cattle and 57 of 336 (17.0%) nonvaccinated cattle were TRM culture positive. From the multilevel logistic model, vaccinated cattle were 92% less likely to be colonized with E. coli O157:H7 than nonvaccinated cattle (odds ratio [OR] = 0.07, p = 0.0008). Additional explanatory variables were region of the state (OR = 7.4, p = 0.04), and pens with fewer cattle (OR = 0.22, p = 0.05). We concluded that the two-dose vaccine regimen effectively reduced the probability for E. coli O157:H7 colonization of the terminal rectum of commercially fed cattle at harvest.
Collapse
Affiliation(s)
- David R Smith
- Department of Veterinary and Biomedical Sciences, University of Nebraska-Lincoln, 68583-0905, USA.
| | | | | | | | | | | | | | | |
Collapse
|
125
|
Maternally and naturally acquired antibodies to Shiga toxins in a cohort of calves shedding Shiga-toxigenic Escherichia coli. Appl Environ Microbiol 2009; 75:3695-704. [PMID: 19363081 DOI: 10.1128/aem.02869-08] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Calves become infected with Shiga toxin-producing Escherichia coli (STEC) early in life, which frequently results in long-term shedding of the zoonotic pathogen. Little is known about the animals' immunological status at the time of infection. We assessed the quantity and dynamics of maternal and acquired antibodies to Shiga toxins (Stx1 and Stx2), the principal STEC virulence factors, in a cohort of 27 calves. Fecal and serum samples were taken repeatedly from birth until the 24th week of age. Sera, milk, and colostrums of dams were also assessed. STEC shedding was confirmed by detection of stx in fecal cultures. Stx1- and Stx2-specific antibodies were quantified by Vero cell neutralization assay and further analyzed by immunoblotting. By the eighth week of age, 13 and 15 calves had at least one stx(1)-type and at least one stx(2)-type positive culture, respectively. Eleven calves had first positive cultures only past that age. Sera and colostrums of all dams and postcolostral sera of all newborn calves contained Stx1-specific antibodies. Calf serum titers decreased rapidly within the first 6 weeks of age. Only five calves showed Stx1-specific seroconversion. Maternal and acquired Stx1-specific antibodies were mainly directed against the StxA1 subunit. Sparse Stx2-specific titers were detectable in sera and colostrums of three dams and in postcolostral sera of their calves. None of the calves developed Stx2-specific seroconversion. The results indicate that under natural conditions of exposure, first STEC infections frequently coincide with an absence of maternal and acquired Stx-specific antibodies in the animals' sera.
Collapse
|
126
|
Thornton AB, Thomson DU, Loneragan GH, Fox JT, Burkhardt DT, Emery DA, Nagaraja TG. Effects of a siderophore receptor and porin proteins-based vaccination on fecal shedding of Escherichia coli O157:H7 in experimentally inoculated cattle. J Food Prot 2009; 72:866-9. [PMID: 19435240 DOI: 10.4315/0362-028x-72.4.866] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The efficacy of a vaccine containing outer membrane siderophore receptor and porin (SRP) proteins for reducing fecal prevalence and shedding of Escherichia coli O157:H7 was evaluated in cattle inoculated with E. coli O157:H7. Thirty calves were randomly assigned to one of two groups, and on days 1 and 21 these calves were given subcutaneous injections of either a placebo (control) or the vaccine. Blood was collected weekly to monitor the serum anti-SRP antibody titers. Two weeks after the second vaccination, calves were orally inoculated with a mixture of five strains of nalidixic acid-resistant (NalR) E. coli O157:H7. Fecal samples and rectoanal mucosal swabs were collected daily for the first 5 days and then three times each week for the following 4 weeks to determine the presence and enumerate the fecal concentration of NalR E. coli O157:H7. At necropsy on day 35, gut contents and tissue swabs were collected to determine the presence and concentration of NalR E. coli O157:H7. Vaccinated cattle had significantly higher anti-SRP antibody titers than did control cattle, with a significant treatment x week interaction (P < 0.01). Vaccination of cattle with the SRP protein tended to decrease fecal concentration (1.9 versus 1.6 log CFU/g) of NalR E. coli O157:H7 (P = 0.10). The number of calves that were fecal culture positive for E. coli O157:H7 was lower (P = 0.05) in the vaccinated group than in the control group. The E. coli O157:H7 SRP vaccine tended to reduce fecal prevalence and concentration of E. coli O157:H7 in cattle orally inoculated with NalR E. coli 0157:H7 and may be a useful prehavest intervention strategy. Future research must be conducted on natural prevalence in feedlot operations to further evaluate the efficacy of this novel vaccine.
Collapse
Affiliation(s)
- A B Thornton
- Department of Clinical Sciences, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas 66506-5606, USA
| | | | | | | | | | | | | |
Collapse
|
127
|
Wells TJ, McNeilly TN, Totsika M, Mahajan A, Gally DL, Schembri MA. The Escherichia coli O157:H7 EhaB autotransporter protein binds to laminin and collagen I and induces a serum IgA response in O157:H7 challenged cattle. Environ Microbiol 2009; 11:1803-14. [PMID: 19508554 DOI: 10.1111/j.1462-2920.2009.01905.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Enterohaemorrhagic Escherichia coli (EHEC) are a subgroup of Shiga toxin-producing E. coli that cause gastrointestinal disease with the potential for life-threatening sequelae. Cattle serve as the natural reservoir for EHEC and outbreaks occur sporadically as a result of contaminated beef and other farming products. While certain EHEC virulence mechanisms have been extensively studied, the factors that mediate host colonization are poorly defined. Previously, we identified four proteins (EhaA,B,C,D) from the prototypic EHEC strain EDL933 that belong to the autotransporter (AT) family. Here we characterize the EhaB AT protein. EhaB was shown to be located at the cell surface and overexpression in E. coli K-12 resulted in significant biofilm formation under continuous flow conditions. Overexpression of EhaB in E. coli K12 and EDL933 backgrounds also promoted adhesion to the extracellular matrix proteins collagen I and laminin. An EhaB-specific antibody revealed that EhaB is expressed in E. coli EDL933 following in vitro growth. EhaB also cross-reacted with serum IgA from cattle challenged with E. coli O157:H7, indicating that EhaB is expressed in vivo and elicits a host IgA immune response.
Collapse
Affiliation(s)
- Timothy J Wells
- School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane Queensland 4072, Australia
| | | | | | | | | | | |
Collapse
|
128
|
Abstract
The prevention of infectious diseases of animals by vaccination has been routinely practiced for decades and has proved to be one of the most cost-effective methods of disease control. However, since the pioneering work of Pasteur in the 1880s, the composition of veterinary vaccines has changed very little from a conceptual perspective and this has, in turn, limited their application in areas such as the control of chronic infectious diseases. New technologies in the areas of vaccine formulation and delivery as well as our increased knowledge of disease pathogenesis and the host responses associated with protection from disease offer promising alternatives for vaccine formulation as well as targets for the prevention of bacterial disease. These new vaccines have the potential to lessen our reliance on antibiotics for disease control, but will only reach their full potential when used in combination with other intervention strategies.
Collapse
|
129
|
Bretschneider G, Berberov EM, Moxley RA. Enteric mucosal antibodies to Escherichia coli O157:H7 in adult cattle. Vet Rec 2009; 163:218-9. [PMID: 18708656 DOI: 10.1136/vr.163.7.218] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Affiliation(s)
- G Bretschneider
- Department of Veterinary and Biomedical Sciences, University of Nebraska, Fair St, East Campus Loop, Lincoln, NE 68583-0905, USA
| | | | | |
Collapse
|
130
|
La Ragione RM, Best A, Woodward MJ, Wales AD. Escherichia coli O157:H7 colonization in small domestic ruminants. FEMS Microbiol Rev 2008; 33:394-410. [PMID: 19207740 DOI: 10.1111/j.1574-6976.2008.00138.x] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Enterohaemorrhagic Escherichia coli O157:H7 was first implicated in human disease in the early 1980s, with ruminants cited as the primary reservoirs. Preliminary studies indicated cattle to be the sole source of E. coli O157:H7 outbreaks in humans; however, further epidemiological studies soon demonstrated that E. coli O157:H7 was widespread in other food sources and that a number of transmission routes existed. More recently, small domestic ruminants (sheep and goats) have emerged as important sources of E. coli O157:H7 human infection, particularly with the widespread popularity of petting farms and the increased use of sheep and goat food products, including unpasteurized cheeses. Although the colonization and persistence characteristics of E. coli O157:H7 in the bovine host have been studied intensively, this is not the case for small ruminants. Despite many similarities to the bovine host, the pathobiology of E. coli O157:H7 in small domestic ruminants does appear to differ significantly from that described in cattle. This review aims to critically review the current knowledge regarding colonization and persistence of E. coli O157:H7 in small domestic ruminants, including comparisons with the bovine host where appropriate.
Collapse
Affiliation(s)
- Roberto M La Ragione
- Department of Food and Environmental Safety, Veterinary Laboratories Agency, Addlestone, Surrey, UK.
| | | | | | | |
Collapse
|
131
|
Franz E, van Bruggen AH. Ecology ofE. coliO157:H7 andSalmonella entericain the Primary Vegetable Production Chain. Crit Rev Microbiol 2008; 34:143-61. [DOI: 10.1080/10408410802357432] [Citation(s) in RCA: 136] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
|
132
|
Chase-Topping M, Gally D, Low C, Matthews L, Woolhouse M. Super-shedding and the link between human infection and livestock carriage of Escherichia coli O157. Nat Rev Microbiol 2008; 6:904-12. [PMID: 19008890 PMCID: PMC5844465 DOI: 10.1038/nrmicro2029] [Citation(s) in RCA: 268] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Cattle that excrete more Escherichia coli O157 than others are known as super-shedders. Super-shedding has important consequences for the epidemiology of E. coli O157 in cattle--its main reservoir--and for the risk of human infection, particularly owing to environmental exposure. Ultimately, control measures targeted at super-shedders may prove to be highly effective. We currently have only a limited understanding of both the nature and the determinants of super-shedding. However, super-shedding has been observed to be associated with colonization at the terminal rectum and might also occur more often with certain pathogen phage types. More generally, epidemiological evidence suggests that super-shedding might be important in other bacterial and viral infections.
Collapse
Affiliation(s)
- Margo Chase-Topping
- Centre for Infectious Diseases, University of Edinburgh, Kings Buildings, Edinburgh, EH9 3JT, UK.
| | | | | | | | | |
Collapse
|
133
|
Smith DR, Moxley RA, Peterson RE, Klopfenstein TJ, Erickson GE, Clowser SL. A Two-Dose Regimen of a Vaccine AgainstEscherichia coliO157:H7 Type III Secreted Proteins Reduced Environmental Transmission of the Agent in a Large-Scale Commercial Beef Feedlot Clinical Trial. Foodborne Pathog Dis 2008; 5:589-98. [DOI: 10.1089/fpd.2008.0080] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- David R. Smith
- Department of Veterinary and Biomedical Sciences, University of Nebraska—Lincoln, Lincoln, Nebraska
| | - Rodney A. Moxley
- Department of Veterinary and Biomedical Sciences, University of Nebraska—Lincoln, Lincoln, Nebraska
| | - Robert E. Peterson
- Department of Animal Science, University of Nebraska—Lincoln, Lincoln, Nebraska
| | | | - Galen E. Erickson
- Department of Animal Science, University of Nebraska—Lincoln, Lincoln, Nebraska
| | - Sharon L. Clowser
- Department of Veterinary and Biomedical Sciences, University of Nebraska—Lincoln, Lincoln, Nebraska
| |
Collapse
|
134
|
Efficient immune responses against Intimin and EspB of enterohaemorragic Escherichia coli after intranasal vaccination using the TLR2/6 agonist MALP-2 as adjuvant. Vaccine 2008; 26:5662-7. [DOI: 10.1016/j.vaccine.2008.07.027] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2008] [Revised: 07/06/2008] [Accepted: 07/14/2008] [Indexed: 01/07/2023]
|
135
|
Epithelial and mesenchymal cells in the bovine colonic mucosa differ in their responsiveness to Escherichia coli Shiga toxin 1. Infect Immun 2008; 76:5381-91. [PMID: 18765725 DOI: 10.1128/iai.00553-08] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Bovine colonic crypt cells express CD77 molecules that potentially act as receptors for Shiga toxins (Stx). The implication of this finding for the intestinal colonization of cattle by human pathogenic Stx-producing Escherichia coli (STEC) remains undefined. We used flow cytometric and real-time PCR analyses of primary cultures of colonic crypt cells to evaluate cell viability, CD77 expression, and gene transcription in the presence and absence of purified Stx1. A subset of cultured epithelial cells had Stx receptors which were located mainly intracellularly, with a perinuclear distribution, and were resistant to Stx1-induced apoptosis and Stx1 effects on chemokine expression patterns. In contrast, a population of vimentin-positive cells, i.e., mesenchymal/nonepithelial cells that had high numbers of Stx receptors on their surface, was depleted from the cultures by Stx1. In situ, CD77(+) cells were located in the lamina propria of the bovine colon by using immunofluorescence staining. A newly established vimentin-positive crypt cell line with high CD77 expression resisted the cytolethal effect of Stx1 but responded to Stx1 with a significant increase in interleukin-8 (IL-8), GRO-alpha, MCP-1, and RANTES mRNA. Combined stimulation with lipopolysaccharide and Stx1 increased IL-10 mRNA. Our results show that bovine colonic crypt cells of epithelial origin are resistant to both the cytotoxic and modulatory effects of Stx1. In contrast, some mucosal mesenchymal cells, preliminarily characterized as mucosal macrophages, are Stx1-responsive cells that may participate in the interaction of STEC with the bovine intestinal mucosa.
Collapse
|
136
|
Abstract
Biosecurity is emerging as a major global health priority for which innovative and unprecedented solutions are needed. Biosecurity is a challenging biocomplexity problem involving multifaceted processes such as interactions between humans and nonhuman biota, anthropogenic environmental and ecological factors, and socioeconomic and political pressures. Key to an effective biosecurity strategy will be fundamental understanding of evolutionary, anthropogenic and environmental driving forces at play in transmission and perpetuation of infectious diseases. Biosecurity solutions will depend on increased support of basic biomedical research and public education, enhanced healthcare preparedness, alternative strategies for ensuringsafety, and improved interagency cooperation regarding global health policy. © 2008 Wiley Periodicals, Inc. Complexity, 2008.
Collapse
|
137
|
Hermesch DR, Thomson DU, Loneragan GH, Renter DR, White BJ. Effects of a commercially available vaccine againstSalmonella entericaserotype Newport on milk production, somatic cell count, and shedding ofSalmonellaorganisms in female dairy cattle with no clinical signs of salmonellosis. Am J Vet Res 2008; 69:1229-34. [DOI: 10.2460/ajvr.69.9.1229] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
|
138
|
Dudley EG. In VivoExpression Technology and Signature-Tagged Mutagenesis Screens for Identifying Mechanisms of Survival of Zoonotic Foodborne Pathogens. Foodborne Pathog Dis 2008; 5:473-85. [DOI: 10.1089/fpd.2008.0104] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Affiliation(s)
- Edward G. Dudley
- Department of Food Science, Penn State University, University Park, Pennsylvania
| |
Collapse
|
139
|
Kudva IT, Calderwood SB, John M. Proteomics-based expression library screening - a platform technology for rapid discovery of pathogen-specific markers of infection. ACTA ACUST UNITED AC 2008; 2:979-89. [PMID: 23495870 DOI: 10.1517/17530059.2.8.979] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND The development of new management modalities is imperative for reducing the global burden of infectious diseases. OBJECTIVE To develop a platform technology for rapid definition of comprehensive pathogen immunoproteomes (the repertoire of microbial proteins that elicit and interact with host immune responses). METHODS Standard molecular biology techniques were coupled with cutting-edge proteomics to develop proteomics-based expression library screening (PELS). RESULTS Proof of principle of PELS was demonstrated by defining a comprehensive immunoproteome of the human gastrointestinal pathogen, Escherichia coli O157:H7, in bovine reservoirs in just 3 weeks. CONCLUSIONS PELS, an immunoproteomics-based platform technology, is a rapid and inexpensive alternative to protein/antigen arrays/chips. It is applicable to any parasitic, fungal, viral or bacterial pathogen (or commensal) that: has a sequenced genome; can be cultured in the laboratory; and elicits host humoral immune responses during the process of infection/disease.
Collapse
Affiliation(s)
- Indira T Kudva
- Massachusetts General Hospital, Division of Infectious Diseases, Boston, MA 02114, USA +1 781 244 4505 ;
| | | | | |
Collapse
|
140
|
Babiuk S, Asper DJ, Rogan D, Mutwiri GK, Potter AA. Subcutaneous and intranasal immunization with type III secreted proteins can prevent colonization and shedding of Escherichia coli O157:H7 in mice. Microb Pathog 2008; 45:7-11. [DOI: 10.1016/j.micpath.2008.01.005] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2007] [Revised: 01/23/2008] [Accepted: 01/25/2008] [Indexed: 10/22/2022]
|
141
|
Dewell GA, Simpson CA, Dewell RD, Hyatt DR, Belk KE, Scanga JA, Morley PS, Grandin T, Smith GC, Dargatz DA, Wagner BA, Salman MD. Impact of transportation and lairage on hide contamination with Escherichia coli O157 in finished beef cattle. J Food Prot 2008; 71:1114-8. [PMID: 18592735 DOI: 10.4315/0362-028x-71.6.1114] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Transportation of cattle from the feedlot to the slaughter plant could influence hide contamination of Escherichia coli O157. A study was initiated to investigate the influence of transportation and lairage on shedding and hide contamination of E. coli O157. Fecal and hide samples were obtained from 40 pens of harvest-ready beef cattle at the feedlot prior to transport and again at the slaughter plant immediately after slaughter. Potential risk factors for hide contamination at the feedlot, during transport, and at slaughter were evaluated. A multilevel Poisson regression model was used to evaluate if transportation and lairage were associated with hide contamination by E. coli O157 in finished beef cattle. Lots of cattle held in E. coli O157-positive lairage pens had eight times greater risk of having positive slaughter hide samples compared with cattle held in culture-negative pens (relative risk, 8.0; 95% confidence interval, 1.6 to 38.8). Lots of cattle that were held in lairage pens contaminated with feces had three times greater risk for positive slaughter hide samples compared with cattle held in clean pens (relative risk, 3.1; 95% confidence interval, 1.2 to 7.9). Lots of cattle that were transported for long distances (> 160.9 km) had twice the risk of having positive hide samples at slaughter compared with cattle transported a shorter distance (relative risk, 2.4; 95% confidence interval, 1.1 to 5.1). These findings suggest that transportation and lairage should be considered in E. coli O157 control strategies.
Collapse
Affiliation(s)
- G A Dewell
- Animal Population Health Institute, Colorado State University, Fort Collins, Colorado 80523, USA
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
142
|
Escherichia coli O157:H7 colonization in cattle following systemic and mucosal immunization with purified H7 flagellin. Infect Immun 2008; 76:2594-602. [PMID: 18362130 DOI: 10.1128/iai.01452-07] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Escherichia coli O157:H7 is an important pathogen of humans. Cattle are most frequently identified as the primary source of infection, and therefore, reduction in E. coli O157:H7 prevalence in cattle by vaccination represents an attractive strategy for reducing the incidence of human disease. H7 flagella have been implicated in intestinal-epithelial colonization of E. coli O157:H7 and may represent a useful target for vaccination. In this study, calves were immunized either systemically with H7 flagellin by intramuscular injection or mucosally via the rectum with either H7 or H7 incorporated into poly(DL-lactide-co-glycolide) microparticles (PLG:H7). Systemic immunization resulted in high levels of flagellin-specific immunoglobulin G (IgG) and IgA in both serum and nasal secretions and detectable levels of both antibody isotypes in rectal secretions. Rectal administration of flagellin resulted in levels of rectal IgA similar to those by the intramuscular route but failed to induce any other antibody response, whereas rectal immunization with PLG:H7 failed to induce any H7-specific antibodies. Following subsequent oral challenge with E. coli O157:H7, reduced colonization rates and delayed peak bacterial shedding were observed in the intramuscularly immunized group compared to nonvaccinated calves, but no reduction in total bacterial shedding occurred. Rectal immunization with either H7 or PLG:H7 had no effect on subsequent bacterial colonization or shedding. Furthermore, purified H7-specific IgA and IgG from intramuscularly immunized calves were shown to reduce intestinal-epithelial binding in vitro. These results indicate that H7 flagellin may be a useful component in a systemic vaccine to reduce E. coli O157:H7 colonization in cattle.
Collapse
|
143
|
Transmission and quantification of verocytotoxin-producing Escherichia coli O157 in dairy cattle and calves. Epidemiol Infect 2008; 137:114-23. [PMID: 18346284 DOI: 10.1017/s0950268808000320] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Data from a field study of 14 months duration in a naturally colonized dairy herd and data from an experiment with calves were used to quantify transmission of verocytotoxin-producing Escherichia coli (VTEC O157) in cattle. For the latter, two groups of 10 calves were randomly assigned and put out in one of two pastures. From each group, five animals were experimentally inoculated with 109 c.f.u. O157 VTEC and, considered infectious, put back in their group. Each of the susceptible contact calves became positive within 6 days of being reunited. The estimate of the basic reproduction ratio (R0) in the experiment was 7.3 (95% CI 3.92-11.5), indicating that each infectious calf will infect seven other calves on average during an assumed infectious period of 28 days in a fully susceptible population. The R0 among dairy cows appeared to be about 10 times lower (0.70, 95% CI 0.48-1.04). After the transmission experiment, six contact-infected animals that were shedding continuously during the experiment were housed in a tie stall during winter. After 40 days, all six tested negative for O157 VTEC. In June, after a period of 34 weeks in which the heifers remained negative, they were put out in a clean and isolated pasture to observe whether they started shedding again. On each pasture that was infected with O157 VTEC during the transmission experiment the previous summer, newly purchased susceptible calves were placed. None of the heifers or calves started shedding during 14 weeks, indicating that both the heifers and the previously contaminated pasture did not function as reservoir of O157 VTEC.
Collapse
|
144
|
Henderson H. Direct and indirect zoonotic transmission of Shiga toxin–producingEscherichia coli. J Am Vet Med Assoc 2008; 232:848-59. [DOI: 10.2460/javma.232.6.848] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
|
145
|
Tabe ES, Oloya J, Doetkott DK, Bauer ML, Gibbs PS, Khaitsa ML. Comparative effect of direct-fed microbials on fecal shedding of Escherichia coli O157:H7 and Salmonella in naturally infected feedlot cattle. J Food Prot 2008; 71:539-44. [PMID: 18389697 DOI: 10.4315/0362-028x-71.3.539] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The effect of direct-fed microbials (DFM) on fecal shedding of Escherichia coli O157:H7 and Salmonella in naturally infected feedlot cattle was evaluated in a clinical trial involving 138 feedlot steers. Following standard laboratory methods, fecal samples collected from steers were evaluated for change in the detectable levels of E. coli O157:H7 and Salmonella shed in feces after DFM treatment. Sampling of steers was carried out every 3 weeks for 84 days. A significant reduction (32%) in fecal shedding of E. coli O157:H7 (P < 0.001), but not Salmonella (P = 0.24), was observed among the treatment steers compared with the control group during finishing. The probability of recovery of E. coli O157:H7 from the feces of treated and control steers was 34.0 and 66.0%, respectively. Steers placed on DFM supplement were almost three times less likely to shed E. coli O157:H7 (odds ratio, 0.36; 95% confidence interval, 0.25 to 0.53; P < 0.001) in their feces as opposed to their control counterparts. The probability of recovery of Salmonella from the feces of the control (14.0%) and the treated (11.3%) steers was similar. However, the DFM significantly reduced probability of new infections with Salmonella among DFM-treated cattle compared with controls (nontreated ones). It appears that DFM as applied in our study are capable of significantly reducing fecal shedding of E. coli O157:H7 in naturally infected cattle but not Salmonella. The factors responsible for the observed difference in the effects of DFM on E. coli O157:H7 and Salmonella warrants further investigation.
Collapse
Affiliation(s)
- Ebot S Tabe
- The Great Plains Institute of Food Safety, North Dakota State University, Fargo, North Dakota 58105-5727, USA
| | | | | | | | | | | |
Collapse
|
146
|
Gerdts V, Littel-van den Hurk SVD, Griebel PJ, Babiuk LA. Use of animal models in the development of human vaccines. Future Microbiol 2008; 2:667-75. [PMID: 18041907 DOI: 10.2217/17460913.2.6.667] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Over the past 100 years, animal infectious disease research has played a crucial role in the development of human vaccines. In fact, many of today's vaccines are based on utilizing animal pathogens, either in the form of an attenuated vaccine or as a vaccine vector. Vaccine development has become increasingly complex with chronic and newly emerging diseases, a demand for therapeutic vaccines for noninfectious diseases, extended vaccine in the neonate and the elderly, and increasing concerns regarding vaccine safety. Furthermore, the evaluation of quantity and quality of immune responses and the ability to efficiently translate the results of basic research into the clinic are critical to ensure that vaccines meet their therapeutic potential. Here, we review the importance of animal models for developing and testing novel human vaccines, discuss the limitations of existing animal models in knowledge translation, and summarize the needs and criteria for future animal models. We argue that efficient translation of basic vaccine research to clinical therapies will depend upon the availability of appropriate animal models to address each of the questions which arise during vaccine development.
Collapse
Affiliation(s)
- Volker Gerdts
- Vaccine & Infectious Disease Organization & Department of Veterinary Microbiology, University of Saskatchewan, 120 Veterinary Rd, Saskatoon, SK S7N 5E3, Canada.
| | | | | | | |
Collapse
|
147
|
Diarrheal disease vaccines. Vaccines (Basel) 2008. [DOI: 10.1016/b978-1-4160-3611-1.50048-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] Open
|
148
|
Abstract
PURPOSE OF REVIEW Shiga toxin-producing Escherichia coli cause hemorrhagic colitis and hemolytic uremic syndrome. We will summarize the literature on incidence and outcomes of these infections, and then review the pathogenesis to explain the current recommendations against antibiotic use and to suggest alternative therapies. RECENT FINDINGS Shiga toxin-producing E. coli continue to be prevalent in the industrialized world because of dissemination in food products contaminated by ruminant feces. Declines in ground beef-related outbreaks have been matched by increased cases related to green vegetables. Fifteen percent of patients infected with E. coli O157:H7 progress to hemolytic uremic syndrome, but this figure may reach 50% if antibiotics are used. Mechanisms for bacteriophage induction causing Shiga toxin production, and for Shiga toxin dissemination to endothelium in gut, kidney and brain, may explain the negative effects of antibiotics and lead to rational therapies. Shiga toxin binders were not effective in clinical trials, but more avid binding agents may be. Current treatment recommendations are to maintain hydration to prevent thrombotic complications. Human vaccines are unlikely to be utilized. Cattle vaccines may prove the most significant approach to this disease. SUMMARY Improved understanding of Shiga toxin-producing Escherichia coli pathophysiology and progression to hemolytic uremic syndrome provides the basis for prevention, prophylactic and treatment strategies.
Collapse
|
149
|
Lavigne JP, Blanc-Potard AB. Molecular evolution of Salmonella enterica serovar Typhimurium and pathogenic Escherichia coli: from pathogenesis to therapeutics. INFECTION GENETICS AND EVOLUTION 2007; 8:217-26. [PMID: 18226587 DOI: 10.1016/j.meegid.2007.11.005] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2007] [Revised: 11/20/2007] [Accepted: 11/22/2007] [Indexed: 12/31/2022]
Abstract
Salmonella enterica serovar Typhimurium (S. Typhimurium) and certain Escherichia coli are human pathogens that have evolved through the acquisition of multiple virulence determinants by horizontal gene transfer. Similar genetic elements, as pathogenicity islands and virulence plasmids, have driven molecular evolution of virulence in both species. In addition, the contribution of prophages has been recently highlighted as a reservoir for pathogenic diversity. Characterization of horizontally acquired virulence genes has several clinical implications. First, identification of virulence determinants that have a sporadic distribution and are specifically associated with a pathotype and/or a pathology can be useful markers for risk assessment and diagnosis. Secondly, virulence factors widely distributed in pathogenic strains, but absent from non-pathogenic bacteria, are interesting targets for the development of novel antimicrobial chemotherapies and vaccines. Here, we summarize the horizontally acquired virulence factors of S. Typhimurium, enterohemorrhagic E. coli O157:H7 and uropathogenic E. coli, and we describe their use in novel therapeutic approaches.
Collapse
Affiliation(s)
- Jean-Philippe Lavigne
- Institut National de la Santé et de la Recherche Médicale, Espri 26, Avenue J.F. Kennedy, 30908 Nîmes Cedex 02, France
| | | |
Collapse
|
150
|
Abstract
Type III secretion systems (T3SSs) are complex bacterial structures that provide gram-negative pathogens with a unique virulence mechanism enabling them to inject bacterial effector proteins directly into the host cell cytoplasm, bypassing the extracellular milieu. Although the effector proteins vary among different T3SS pathogens, common pathogenic mechanisms emerge, including interference with the host cell cytoskeleton to promote attachment and invasion, interference with cellular trafficking processes, cytotoxicity and barrier dysfunction, and immune system subversion. The activity of the T3SSs correlates closely with infection progression and outcome, both in animal models and in human infection. Therefore, to facilitate patient care and improve outcomes, it is important to understand the T3SS-mediated virulence processes and to target T3SSs in therapeutic and prophylactic development efforts.
Collapse
|