SU-E-T-25: Real Time Simulator for Designing Electron Dual Scattering Foil Systems

PURPOSE

To create a user friendly, accurate, real time computer simulator to facilitate the design of dual foil scattering systems for electron beams on radiotherapy accelerators. The simulator should allow for a relatively quick, initial design that can be refined and verified with subsequent Monte Carlo (MC) calculations and measurements.

METHODS

The simulator consists of an analytical algorithm for calculating electron fluence and a graphical user interface (GUI) C++ program. The algorithm predicts electron fluence using Fermi-Eyges multiple Coulomb scattering theory with a refined Moliere formalism for scattering powers. The simulator also estimates central-axis x-ray dose contamination from the dual foil system. Once the geometry of the beamline is specified, the simulator allows the user to continuously vary primary scattering foil material and thickness, secondary scattering foil material and Gaussian shape (thickness and sigma), and beam energy. The beam profile and x-ray contamination are displayed in real time.

RESULTS

The simulator was tuned by comparison of off-axis electron fluence profiles with those calculated using EGSnrc MC. Over the energy range 7-20 MeV and using present foils on the Elekta radiotherapy accelerator, the simulator profiles agreed to within 2% of MC profiles from within 20 cm of the central axis. The x-ray contamination predictions matched measured data to within 0.6%. The calculation time was approximately 100 ms using a single processor, which allows for real-time variation of foil parameters using sliding bars.

CONCLUSIONS

A real time dual scattering foil system simulator has been developed. The tool has been useful in a project to redesign an electron dual scattering foil system for one of our radiotherapy accelerators. The simulator has also been useful as an instructional tool for our medical physics graduate students.

Assessing renal parenchymal volume on unenhanced CT as a marker for predicting renal function in patients with chronic kidney disease

OBJECTIVES

To estimate renal volume in chronic kidney disease (CKD) patients using a semiautomated software and compare them with split renal function estimates from radionuclide renogram (RR). We proposed that renal volume from unenhanced computed tomography (CT) scans may serve as surrogate marker for assessing renal function in CKD patients.

MATERIALS AND METHODS

Unenhanced multidetector CT scans of 26 patients with CKD (estimated glomerular filtration rate [eGFR] <60 mL/kg/body surface area [BSA]) and 10 controls (eGFR >60 mL/kg/BSA) were analyzed to calculate renal volumes using a semiautomated software (AMIRAV5.2.0). Volumes obtained were then correlated with corresponding eGFR and split renal function estimates from RR. Volumes were also compared with those obtained on enhanced scans in 10 cases (five disease group, five controls). Bland-Altman analysis was used to assess agreement between methods.

RESULTS

A moderately positive correlation was found between renal volume obtained on unenhanced CT and eGFR (r = 0.65, P < .0001), whereas a significantly high correlation with split function estimates from RR (r = 0.95, P < .001) was found. Bland-Altman analysis revealed a good agreement between renal volume from CT and renal function from RR (34/36 observations were within 95% CI and there were two outliers). Correlation between volumes obtained from unenhanced and enhanced CT scans was also significant (r = 0.96).

CONCLUSION

In patients with CKD, renal volume derived from unenhanced CT can possibly serve as a surrogate marker for assessing and monitoring renal function reserves to plan further management.

Consensus recommendations for current treatments and accelerating clinical trials for patients with neurofibromatosis type 2

Neurofibromatosis type 2 (NF2) is a tumor suppressor syndrome characterized by bilateral vestibular schwannomas (VS) which often result in deafness despite aggressive management. Meningiomas, ependymomas, and other cranial nerve and peripheral schwannomas are also commonly found in NF2 and collectively lead to major neurologic morbidity and mortality. Traditionally, the overall survival rate in patients with NF2 is estimated to be 38% at 20 years from diagnosis. Hence, there is a desperate need for new, effective therapies. Recent progress in understanding the molecular basis of NF2 related tumors has aided in the identification of potential therapeutic targets and emerging clinical therapies. In June 2010, representatives of the international NF2 research and clinical community convened under the leadership of Drs. D. Gareth Evans (University of Manchester) and Marco Giovannini (House Research Institute) to review the state of NF2 treatment and clinical trials. This manuscript summarizes the expert opinions about current treatments for NF2 associated tumors and recommendations for advancing therapies emerging from that meeting. The development of effective therapies for NF2 associated tumors has the potential for significant clinical advancement not only for patients with NF2 but for thousands of neuro-oncology patients afflicted with these tumors.

An analysis of listening skills of healthcare students in Nigeria

BACKGROUND

Listening is a primary communication skill essential for human learning and reported to be positively correlated with school achievement. It enables the healthcare professional to explore fully the ideas and concerns of the patient during a healthcare encounter. It is especially needed by healthcare students and professionals in light of the study showing that the typical physician will interrupt a patient after about 18-23 seconds.

OBJECTIVE

The objective of this study was to measure the listening skills of the undergraduate health sciences students in a Nigerian setting and to attempt to explain different levels of individual listening skills.

METHODS

Selected undergraduate students in medicine, dentistry, nursing and physiotherapy who volunteered to complete a self-administered questionnaire were studied. The questionnaire contained seventeen items, ranked on a 5-point Likert scale on the various habits people adopt when listening to others and the students' three most recent academic test scores.

RESULTS

The mean (SD) score for the seventeen items was 2.72 (1.14) out of 5. Seven items had mean scores greater than 3.00, eight items had mean scores between 2.00 and 3.00, and two items had mean less than 2.00. The students had a minimum score of 27 and a maximum score of 67 compared with a possible 17 and 85. The mean (SD) score for the listening scale by the students was 46.87 (7.33). Eighty percent of the respondents had good listening skills. There were no statistically significant associations between the listening skills scores of the students and several possible explanatory variables - age, gender, course being studied and test scores.

CONCLUSION

The findings indicate that neither males nor females are the better listeners. It showed impressively high levels of listening skills among the respondents. There was the absence of explanatory variables which were significant in explaining differences between individual listening skill scores.

Analysis of the perception of institutional culture for health sector reform in Nigeria

Purpose

The purpose of this paper is to analyse the perception of institutional culture in four hospitals in Nigeria and its influence on the implementation of the health sector reform programme in the country.

Design/methodology/approach

A cross‐sectional study of 507 healthcare professionals and managers using a self‐administered questionnaire was carried our.

Findings

The overall perception of institutional culture was above average at 56.4 per cent. The perceptions of the two dimensions of institutional culture were: leadership 59.3 per cent and character 54.0 per cent. Two out of the 11 statements on institutional culture had levels of perception that were lower than 50 per cent. These were: “staff morale and job satisfaction are high at all levels, and regularly evaluated by the institution” (41.6 per cent) and “information is shared openly in the institution” (44.3 per cent).

Originality/value

There is a need to strengthen the character dimension of the institutional culture of Nigerian hospitals, especially staff morale and job satisfaction as well as the sharing of information in the hospitals.

Preparation and Characterization of Mn0.4Ni x Zn0.6−x Fe2O4 Soft Spinel Ferrites for Low and High Frequency Applications by Citrate Precursor Method

In the present study, preparation and characterization of Mn-Ni-Zn soft ferrites with chemical formula Mn0.4Ni x Zn0.6−x Fe2O4, where x = 0.0, 0.2 and 0.4, by citrate precursor method has been reported. Microstructural properties studied with the help of X-ray diffraction and scanning electron microscopy show that the samples have almost uniform sized crystallites and have single phase spinel structure. The properties like initial permeability, permeability loss, dielectric constant, dielectric loss are studied as a function of frequency. The d.c. resistivity of the samples is also studied. Variation of d.c. resistivity with composition, x, of the ferrite sample shows that pure zinc ferrite has more resistivity than that of nickel substituted zinc ferrite. The dispersion in the magnetic and electrical properties has been discussed by using various mechanisms, models and theories.

Consensus recommendations to accelerate clinical trials for neurofibromatosis type 2

PURPOSE

Neurofibromatosis type 2 (NF2) is a rare autosomal dominant disorder associated primarily with bilateral schwannomas seen on the superior vestibular branches of the eighth cranial nerves. Significant morbidity can result from surgical treatment of these tumors. Meningiomas, ependymomas, and other benign central nervous system tumors are also common in NF2. The lack of effective treatments for NF2 marks an unmet medical need.

EXPERIMENTAL DESIGN

Here, we provide recommendations from a workshop, cochaired by Drs. D. Gareth Evans and Marco Giovannini, of 36 international researchers, physicians, representatives of the biotechnology industry, and patient advocates on how to accelerate progress toward NF2 clinical trials.

RESULTS

Workshop participants reached a consensus that, based on current knowledge, the time is right to plan and implement NF2 clinical trials. Obstacles impeding NF2 clinical trials and how to address them were discussed, as well as the candidate therapeutic pipeline for NF2.

CONCLUSIONS

Both phase 0 and phase II NF2 trials are near-term options for NF2 clinical trials. The number of NF2 patients in the population remains limited, and successful recruitment will require ongoing collaboration efforts between NF2 clinics.

Chloracne in seven organic chemists exposed to novel polycyclic halogenated chemical compounds (triazoloquinoxalines)

Chloracne is an acneiform eruption caused though poisoning by aromatic compounds (usually halogenated) showing a specific molecular configuration. We describe an outbreak of chloracne among seven discovery chemists who synthesized novel polycyclic halogenated chemical compounds which were classified as triazoloquinoxalines, not known to be chloracnegenic. The diagnosis of chloracne, made clinically, elicited a thorough risk assessment and monitoring programme by the occupational health department. The chemists were investigated by serum excretion rates, skin sampling for Propionibacterium acnes, skin biopsy and laboratory blood investigations. Sebum excretion was normal in five cases, raised in one case and severely reduced in another. Skin levels of P. acnes were normal in all patients except for the one subject who had low sebum excretion, in whom they were undetectable. One subject had a slightly raised serum level of alanine aminotransferase. There were no other signs of systemic toxicity. Two subjects were treated with an oral antibiotic, two received topical therapy only and three required no treatment at all. The patients have had thorough health surveillance at 6-monthly and yearly intervals. In each case the chloracne mostly resolved within 18-24 months although on examination about 3 years later, five of the seven still showed minor changes of chloracne. This outbreak emphasizes the need for vigilance in discovery science. The triazoloquinoxalines were not previously recognized as being chloracnegens although their chemical characteristics were subsequently identified as being in keeping with other chemicals that can cause chloracne. Chloracne can be a difficult diagnosis to make when it occurs in a novel setting: occupational physicians and dermatologists need to be vigilant when dealing with unusual eruptions in discovery chemists.

Cyclooxygenase-2 selective non-steroidal anti-inflammatory drugs (etodolac, meloxicam, celecoxib, rofecoxib, etoricoxib, valdecoxib and lumiracoxib) for osteoarthritis and rheumatoid arthritis: a systematic review and economic evaluation

OBJECTIVES

To review the clinical effectiveness and cost-effectiveness of cyclooxygenase-2 (COX-2) selective non-steroidal anti-inflammatory drugs (NSAIDs) (etodolac, meloxicam, celecoxib, rofecoxib, etoricoxib, valdecoxib and lumiracoxib) for osteoarthritis (OA) and rheumatoid arthritis (RA).

DATA SOURCES

Electronic databases were searched up to November 2003. Industry submissions to the National Institute for Health and Clinical Excellence (NICE) in 2003 were also reviewed.

REVIEW METHODS

Systematic reviews of randomised controlled trials (RCTs) and a model-based economic evaluation were undertaken. Meta-analyses were undertaken for each COX-2 selective NSAID compared with placebo and non-selective NSAIDs. The model was designed to run in two forms: the 'full Assessment Group Model (AGM)', which includes an initial drug switching cycle, and the 'simpler AGM', where there is no initial cycle and no opportunity for the patient to switch NSAID.

RESULTS

Compared with non-selective NSAIDs, the COX-2 selective NSAIDs were found to be equally as efficacious as the non-selective NSAIDs (although meloxicam was found to be of inferior or equivalent efficacy) and also to be associated with significantly fewer clinical upper gastrointestinal (UGI) events (although relatively small numbers of clinical gastrointestinal (GI) and myocardial infarction (MI) events were reported across trials). Subgroup analyses of clinical and complicated UGI events and MI events in relation to aspirin use, steroid use, prior GI history and Helicobacter pylori status were based on relatively small numbers and were inconclusive. In the RCTs that included direct COX-2 comparisons, the drugs were equally tolerated and of equal efficacy. Trials were of insufficient size and duration to allow comparison of risk of clinical UGI events, complicated UGI events and MIs. One RCT compared COX-2 (celecoxib) with a non-selective NSAID combined with a gastroprotective agent (diclofenac combined with omeprazole); this included arthritis patients who had recently suffered a GI haemorrhage. Although no significant difference in clinical GI events was reported, the number of events was small and more such studies, where patients genuinely need NSAIDs, are required to confirm these data. A second trial showed that rofecoxib was associated with fewer diarrhoea events than a combination of diclofenac and misoprostol (Arthrotec). Previously published cost-effectiveness analyses indicated a wide of range of possible incremental cost per quality-adjusted life-year (QALY) gained estimates. Using the simpler AGM, with ibuprofen or diclofenac alone as the comparator, all of the COX-2 products are associated with higher costs (i.e. positive incremental costs) and small increases in effectiveness (i.e. positive incremental effectiveness), measured in terms of QALYs. The magnitude of the incremental costs and the incremental effects, and therefore the incremental cost-effectiveness ratios, vary considerably across all COX-2 selective NSAIDs. The base-case incremental cost per QALY results for COX-2 selective NSAIDs compared with diclofenac for the simpler model are: celecoxib (low dose) 68,400 pounds; celecoxib (high dose) 151,000 pounds; etodolac (branded) 42,400 pounds; etodolac (generic) 17,700 pounds; etoricoxib 31,300 pounds; lumiracoxib 70,400 pounds; meloxicam (low dose) 10,300 pounds; meloxicam (high dose) 17,800 pounds; rofecoxib 97,400 pounds; and valdecoxib 35,500 pounds. When the simpler AGM was run using ibuprofen or diclofenac combined with proton pump inhibitor (PPI) as the comparator, the results change substantially, with the COX-2 selective NSAIDs looking generally unattractive from a cost-effectiveness point of view (COX-2 selective NSAIDs were dominated by ibuprofen or diclofenac combined with PPI in most cases). This applies both to 'standard' and 'high-risk' arthritis patients defined in terms of previous GI ulcers. The full AGM produced results broadly in line with the simpler model.

CONCLUSIONS

The COX-2 selective NSAIDs examined were found to be similar to non-selective NSAIDs for the symptomatic relief of RA and OA and to provide superior GI tolerability (the majority of evidence is in patients with OA). Although COX-2 selective NSAIDs offer protection against serious GI events, the amount of evidence for this protective effect varied considerably across individual drugs. The volume of trial evidence with regard to cardiovascular safety also varied substantially between COX-2 selective NSAIDs. Increased risk of MI compared to non-selective NSAIDs was observed among those drugs with greater volume of evidence in terms of exposure in patient-years. Economic modelling shows a wide range of possible costs per QALY gained in patients with OA and RA. Costs per QALY also varied if individual drugs were used in 'standard' or 'high'-risk patients, the choice of non-selective NSAID comparator and whether that NSAID was combined with a PPI. With reduced costs of PPIs, future primary research needs to compare the effectiveness and cost-effectiveness of COX-2 selective NSAIDs relative to non-selective NSAIDs with a PPI. Direct comparisons of different COX-2 selective NSAIDs, using equivalent doses, that compare GI and MI risk are needed. Pragmatic studies that include a wider range of people, including the older age groups with a greater burden of arthritis, are also necessary to inform clinical practice.

Inhibition of airway eosinophilia and pulmonary pathology in a mouse model of allergic asthma by the live vaccine strain of Francisella tularensis

BACKGROUND

It has been suggested that exposure to certain microbes and their products, particularly during neonatal and early childhood periods, may shift the immune response towards a T-helper cell (Th) 1 phenotype and thereby prevent the development of and/or alleviate the clinical symptoms of allergic airway diseases.

OBJECTIVE

We evaluated the ability of the live vaccine strain (LVS) of Francisella tularensis to suppress airway eosinophilia and pulmonary pathology in a murine model of allergic airway disease.

METHODS

C57BL/6 mice were sensitized by intraperitoneal injection of ovalbumin (OVA) on days 1 and 14, and challenged intranasally (i.n.) with OVA on day 21 or thereafter. Some sensitized mice were i.n. treated with live LVS or its cell-free sonicate extract (CFSE) before i.n. OVA challenge. Bronchoalveolar lavage fluid, regional lymph node cells, lung tissues and serum samples were collected 3-7 days after the i.n. challenge.

RESULTS

Intranasal and, to a lesser degree, intradermal immunization of OVA-sensitized mice with LVS suppressed the development of airway eosinophilia and associated pulmonary pathology induced by i.n. OVA challenge. Moreover, CFSE prepared from LVS showed a similar inhibitory effect whereas neither LPS nor DNA purified from F. tularensis LVS had such an effect. The inhibition was associated with the reduction in mRNA expression and protein levels of Th2 cytokines IL-5 and IL-13 in the lungs and the enhanced production of OVA-induced IFN-gamma by local draining lymph node cells, but not with the serum levels of OVA-specific IgG1 or IgE.

CONCLUSION

F. tularensis LVS is capable of suppressing allergic airway inflammation probably through a Th1-mediated suppression of an ongoing Th2 response mechanism, and raises the possibility of exploring LVS and its components as potential therapeutic modalities for human allergic asthma.

The Met Office Hadley Centre climate modelling capability: the competing requirements for improved resolution, complexity and dealing with uncertainty

Predictions of future climate change require complex computer models of the climate system to represent the full range of processes and interactions that influence climate. The Met Office Hadley Centre uses 'families' of models as part of the Met Office Unified Model Framework to address different classes of problems. The HadGEM family is a suite of state-of-the-art global environment models that are used to reduce uncertainty and represent and predict complex feedbacks. The HadCM3 family is a suite of well established but cheaper models that are used for multiple simulations, for example, to quantify uncertainty or to test the impact of multiple emissions scenarios.

Tri-axial plantar pressure sensor: design, calibration and characterization

A novel tri-axial plantar pressure sensor has been developed. This sensor simultaneously measures vertical plantar pressure and anterior-posterior and medial-lateral shear plantar pressures utilizing a central post, four parallel plates, and a commercial miniature pressure transducer. As a subject walks over the sensor, the central post is deflected and the shear pressures are measured utilizing capacitive sensing technology. The miniature pressure transducer (MPT) is simultaneously loaded to measure the vertical pressure. Each individual tri-axial plantar pressure sensor has the capability of measuring shear forces ranging from 0 to 15 N and vertical pressures ranging from 0 to 28 MPa. The shear component of the tri-axial pressure sensor has a sensitivity of 1.3 mV/g, a non-linearity of 8.3 %, and hysteresis of 7.3 %. The commercial vertical MPT has a sensitivity of 220 nv/V/psi, a non-linearity of 0.094%, and a hysteresis of 0.567%. An array of individual tri-axial plantar pressure sensors in the form of a platform will be developed to measure plantar pressure in patients. This pressure platform is placed on the surface of a walkway and is suitable for barefoot walking trials.

Dynamic-threshold level set method for volumetry of porcine kidney in CT images in vivo and ex vivo assessment of the accuracy of volume measurement

RATIONALE AND OBJECTIVE

We sought to assess the accuracy of a novel computerized volumetry method, called dynamic-thresholding (DT) level set, in determining the renal volume of pigs in CT images on the basis of in vivo and ex vivo reference standards.

METHODS AND MATERIALS

Eight Yorkshire breed anesthetized pigs (weight range 45-50 kg) were scanned on a 64-slice multidetector CT scanner (Sensation 64; Siemens) after injection of an iodinated (300 mg I/ml) contrast agent through an IV cannula. The kidneys of the pigs were then surgically resected and scanned by CT in the same manner. Both in vivo and ex vivo CT images were subjected to our computerized volumetry using DT level set method. The resulting volumes of the kidneys were compared with in vivo and ex vivo reference standards: the former was established by manual contouring of the kidneys on the CT images by an experienced radiologist, and the latter was established as the water displacement volume of the resected kidney.

RESULTS

The comparisons of the in vivo and ex vivo measurements by our volumetric scheme with the associated reference standards yielded a mean difference of 1.73 +/- 1.24% and 3.38 +/- 2.51%, respectively. The correlation coefficients were 0.981 and 0.973 for in vivo and ex vivo comparisons, respectively. The mean difference between in vivo and ex vivo reference standards was 5.79 +/- 4.26%, and the correlation coefficient between the two standards was 0.760.

CONCLUSION

Our computerized volumetry using the DT level set method can provide accurate in vivo and ex vivo measurements of kidney volume, despite a large difference between the two reference standards. This technique can be employed in human subjects for the determination of renal volume for preoperative surgical planning and assessment of oncology treatment.

Biomechanics of femoral deformity in osteogenesis imperfecta (OI): a quantitative approach to rehabilitation

Skeletal deformity is an important characteristic of osteogenesis imperfecta (OI). To study the influence of deformity in stress/strain distribution, a finite element analysis (TEA) of the femur during physiological loading was developed. The diaphysis was altered mathematically to reflect different clinical deformities of OI. Joint reaction and muscle forces were adapted from the literature to reproduce the loading environment at 10% gait cycle (loading response, LR). The goal of the study was to quantitatively describe the stress/strain distribution while comparing the extent of deformity. The results showed that deformity could deteriorate the stress/strain distribution. The study offers a quantitative means for rehabilitative intervention.

The effect of induced stress on the relationship between perfectionism and unhealthy eating attitudes

It has previously been shown that stress situations reveal an association between perfectionism and unhealthy eating attitudes in nonclinical females. The present study aimed to extend these findings by also measuring psychological and physiological reactions to induced stress. Forty-two female university students completed measures of state anxiety, perfectionism and unhealthy eating attitudes on two occasions: an average day and after a task designed to induce stress. Physiological responses to stress were measured before, and immediately after the task. Whilst Body Dissatisfaction was associated with aspects of perfectionism both at baseline and immediately after the stress task, Drive for Thinness was only associated with Concern over Mistakes and Personal Standards after the task. These findings confirm previous work showing that stress encourages a relationship between disturbed eating behaviours and perfectionism and therefore, have implications for prevention and early intervention programmes for eating disorders.

Dysfunctional Core Beliefs in Eating Disorders: A Review

Until recently, it was widely accepted that eating-disordered symptoms are caused and maintained by patterns of maladaptive thinking (negative automatic thoughts and dysfunctional assumptions) regarding body size, shape, and weight. However, current research and clinical investigations suggest that broader patterns of maladaptive thinking exist in cognitive organization of eating psychopathology and that cognitive therapy for eating disorders might benefit from in-depth consideration of the individual’s cognitive content. For these reasons, research into the impact of core beliefs in eating disorders has increased in recent years. This article provides a review and critique of the existing findings. The main methodological problems of examining core beliefs in eating disorders are discussed, and the conceptual issues that arise in this area are also reviewed. Finally, suggestions for the directions of future research are also made.

Rehabilitative orthotics evaluation in children with diplegic cerebral palsy: kinematics and kinetics

Ankle foot orthoses (AFOs) are prescribed for ambulatory children with spastic diplegia to improve biomechanical alignment and functional capability. The purpose of this study was to employ quantitative motion analysis of the lower extremity to investigate two rehabilitative orthotics. The effects of hinged ankle foot orthoses (HAFO) and dynamic ankle foot orthoses (DAFO) for joint ankle management in children with cerebral palsy were compared. Sixteen (16) independently ambulatory children with a diagnosis of spastic diplegic cerebral palsy (7.5 +/- 2.9 yrs.) were included in the study. The biomechanical effects of two AFO designs were compared to barefoot using a 3-D motion analysis system. Significant differences between braced and unbraced conditions were found in peak ankle dorsiflexion, and peak ankle plantarflexion, knee stance peak flexion, knee swing peak flexion, hip stance peak flexion, and peak ankle plantarflexion moment (p < 0.01). Differences between the HAFO and DAFO were not seen in the kinematic and kinetic metrics. Further development of dynamic testing is suggested in order to advance our understanding of orthotic intervention. The value of quantitative description of gait dynamics is clearly indicated for rehabilitative application.

Mouse model of oral infection with virulent type A Francisella tularensis

Francisella tularensis is a gram-negative facultative intracellular pathogen and the causative agent of tularemia. Little is known about the immunopathogenesis of oral infection with this pathogen. Here, for the first time, we examined the susceptibility of mice to intragastric inoculation with virulent type A F. tularensis and characterized the course of infection and the associated host responses. Both immunocompetent and immunodeficient mice were relatively susceptible to intragastric inoculation of type A F. tularensis with a 50% lethal dose (LD(50)) of 10(6) organisms, which was 100,000-fold higher than the LD(100) for intradermal or respiratory routes of infection. Mice deficient in gamma interferon or tumor necrosis factor receptors 1 and 2 were more susceptible than wild-type controls to oral infection with a high dose of the pathogen. After oral inoculation, F. tularensis appeared first in the mesenteric lymph nodes (MLN) and then rapidly spread to the livers and spleens, where the organism multiplied to high numbers and induced marked neutrophilic infiltration and severe tissue necrosis. Infected mice showed rapid increases in tissue cytokine mRNA expression, which peaked in the MLN at 2 days postinfection (dpi) and in the liver and spleen at 3 dpi. The levels of gamma interferon, interleukin-1beta (IL-1beta), IL-6, tumor necrosis factor alpha, macrophage inflammatory protein 1alpha, KC, interferon-inducible protein 10, and monocyte chemotactic protein 1 were elevated from day 2 postinoculation onward. Moreover, mice intradermally immunized with the live vaccine strain of F. tularensis showed little survival advantage over naive mice after oral challenge with type A F. tularensis. These results suggest that type A F. tularensis is an effective oral pathogen that can cause fatal systemic infection and could pose a public health concern, particularly to immunocompromised individuals, if ingested in contaminated water and food.