Development, Characterization, and Standardization of a Nose-Only Inhalation Exposure System for Exposure of Rabbits to Small-Particle Aerosols Containing Francisella tularensis.

Inhalation of Francisella tularensis causes pneumonic tularemia in humans, a severe disease with a 30 to 60% mortality rate. The reproducible delivery of aerosolized virulent bacteria in relevant animal models is essential for evaluating medical countermeasures. Here we developed optimized protocols for infecting New Zealand White (NZW) rabbits with aerosols containing F. tularensis We evaluated the relative humidity, aerosol exposure technique, and bacterial culture conditions to optimize the spray factor (SF), a central metric of aerosolization. This optimization reduced both inter- and intraday variability and was applicable to multiple isolates of F. tularensis Further improvements in the accuracy and precision of the inhaled pathogen dose were achieved through enhanced correlation of the bacterial culture optical density and the number of CFU. Plethysmograph data collected during exposures found that respiratory function varied considerably between rabbits, was not a function of weight, and did not improve with acclimation to the system. Live vaccine strain (LVS)-vaccinated rabbits were challenged via aerosol with human-virulent F. tularensis SCHU S4 that had been cultivated in either Mueller-Hinton broth (MHB) or brain heart infusion (BHI) broth. LVS-vaccinated animals challenged with SCHU S4 that had been cultivated in MHB experienced short febrile periods (median, 3.2 days), limited weight loss (<5%), and longer median survival times (∼18 days) that were significantly different from those for unvaccinated controls. In contrast, LVS-vaccinated rabbits challenged with SCHU S4 that had been cultivated in BHI experienced longer febrile periods (median, 5.5 days) and greater weight loss (>10%) than the unvaccinated controls and median survival times that were not significantly different from those for the unvaccinated controls. These studies highlight the importance of careful characterization and optimization of protocols for aerosol challenge with pathogenic agents.

Human Dose-Response Data for Francisella tularensis and a Dose- and Time-Dependent Mathematical Model of Early-Phase Fever Associated with Tularemia After Inhalation Exposure.

Military health risk assessors, medical planners, operational planners, and defense system developers require knowledge of human responses to doses of biothreat agents to support force health protection and chemical, biological, radiological, nuclear (CBRN) defense missions. This article reviews extensive data from 118 human volunteers administered aerosols of the bacterial agent Francisella tularensis, strain Schu S4, which causes tularemia. The data set includes incidence of early-phase febrile illness following administration of well-characterized inhaled doses of F. tularensis. Supplemental data on human body temperature profiles over time available from de-identified case reports is also presented. A unified, logically consistent model of early-phase febrile illness is described as a lognormal dose-response function for febrile illness linked with a stochastic time profile of fever. Three parameters are estimated from the human data to describe the time profile: incubation period or onset time for fever; rise time of fever; and near-maximum body temperature. Inhaled dose-dependence and variability are characterized for each of the three parameters. These parameters enable a stochastic model for the response of an exposed population through incorporation of individual-by-individual variability by drawing random samples from the statistical distributions of these three parameters for each individual. This model provides risk assessors and medical decisionmakers reliable representations of the predicted health impacts of early-phase febrile illness for as long as one week after aerosol exposures of human populations to F. tularensis.

A human macrophage-hepatocyte co-culture model for comparative studies of infection and replication of Francisella tularensis LVS strain and subspecies holarctica and mediasiatica.

BACKGROUND: Francisella tularensis, a gram-negative bacterium replicates intracellularly within macrophages and efficiently evades the innate immune response. It is able to infect and replicate within Kupffer cells, specialized tissue macrophages of the liver, and to modulate the immune response upon infection to its own advantage. Studies on Francisella tularensis liver infection were mostly performed in animal models and difficult to extrapolate to the human situation, since human infections and clinical observations are rare. RESULTS: Using a human co-culture model of macrophages and hepatocytes we investigated the course of infection of three Francisella tularensis strains (subspecies holarctica--wildtype and live vaccine strain, and mediasiatica--wildtype) and analyzed the immune response triggered upon infection. We observed that hepatocytes support the intracellular replication of Franciscella species in macrophages accompanied by a specific immune response inducing TNFα, IL-1ß, IL-6 and fractalkine (CX3CL1) secretion and the induction of apoptosis. CONCLUSIONS: We could demonstrate that this human macrophage/hepatocyte co-culture model reflects strain-specific virulence of Francisella tularensis. We developed a suitable tool for more detailed in vitro studies on the immune response upon liver cell infection by F. tularensis.

[Epizootic and epidemic manifestation of natural foci of tularemia in Moscow region (1965-2013)].

AIM: Detection of contemporary features of tularemia focimanifestations, determination of territories of high epidemic risk in various landscape zones and creation of a map of foci territories of Moscow Region for isolation of tularemia infectious agent cultures and registered human morbidity for justified planning of prophylaxis measures. MATERIALS AND METHODS: Report materials of epizootologic examinations of natural foci for 1965-2013, 156 maps of epidemiologic examination of cases of human infection with tularemia, results of studies of casting of predatory birds and dung of predatory mammals were used. Registered morbidity and isolation of tularemia infectious agent cultures from 1965 to date were applied to an electronic map of Moscow Region by sign method using modern. GIS-technologies (MapInfo 10.5 program). Electronic maps Ingit at 1:200,000 scale, as well as Google Earth program were used to search for base points. RESULTS: Analysis of morbidity has revealed structure change in human tularemia morbidity--an increase of the fraction of urban population and a decrease of the fraction of patients among rural inhabitants, unimmunized against this infection are mostly ill. The presence of DNA of tularemia causative agent in biological objects in the complex with serologic and bacteriological studies was shown to allow to detect flaccid epizootics even at low numbers of rodents. CONCLUSION: Cartographic reflection of registered morbidity and isolation of tularemia infectious agent cultures allowed to show territories with various degrees of epizootic activity and epidemic manifestation. Positive results of serologic and molecular-genetic studies of environmental objects gives evident on epizootic activity and constant risk of aggravation of epidemic situation for this infection.

Tularaemia in Berlin - two independent cases in travellers returning from central Anatolia, Turkey, February 2011.

Tularaemia, though rare, has recently been increasingly reported in Germany. Most cases are indigenous infections. This report describes two epidemiologically independent infections with Francisella tularensis subspecies holarctica detected in Berlin in February 2011 that were acquired in central Anatolia, Turkey. In Turkey, there have been repeated tularaemia outbreaks since 2000 and the disease should therefore be considered as a differential diagnosis in travellers returning from that country.

Tularemia: A rare cause of pediatric lymph nodes adenitis.

Adenopathy in pediatrics can have many different causes: infectious, tumoral, and inflammatory. We report the case of an 8-year-old patient with a febrile popliteal ulceration associated with an inflammatory satellite inguinal lymph node adenitis. Serological tests and polymerase chain reaction analyses confirmed the diagnosis of ulceroglandular tularemia. An appropriate antimicrobial therapy led to a full recovery. This case reminds us to consider tularemia as a potential emergent disease in children presenting with subacute to chronic lymphadenopathy and thereby to choose the correct diagnostic tool and appropriate antimicrobial therapy.

You're the Flight Surgeon.

Warneke J, Pavelites J. You're the flight surgeon: tularemia. Aerosp Med Hum Perform. 2020; 91(5):379-381.

Substituted diphenyl ethers as a broad-spectrum platform for the development of chemotherapeutics for the treatment of tularaemia.

OBJECTIVES: The National Institute of Allergy and Infectious Disease classifies Francisella tularensis as a Category A priority pathogen. Despite the availability of drugs for treating tularaemia, the mortality in naturally acquired cases can still approach 30%. In addition, the usefulness of existing drugs for treatment in response to exposure or for prophylaxis is limited because of toxicity and delivery concerns. The aim of this study was to assess the efficacy of the lead alkyl-substituted diphenyl ether, SBPT04, in the F. tularensis murine model of infection. METHODS: SBPT04 was delivered by intraperitoneal (ip) and oral (po) routes, and mice were monitored for morbidity, mortality and relapse of disease. Pharmacokinetic studies were performed to evaluate bioavailability. Phase I and Phase II metabolism of SBPT04 was assessed in mouse and human microsomes. RESULTS: SBPT04, a potent inhibitor of the enoyl-ACP reductase enzyme ftuFabI, has efficacy against F. tularensis in the murine model of infection when delivered by both ip and po routes. SBPT04 delivered ip cleared infection by day 4 of treatment, and SBPT04 delivered po resulted in delayed dissemination. Importantly, SBPT04 delivered ip or po demonstrated efficacy with no signs of relapse of disease. Pharmacokinetic studies show increased serum concentrations following ip delivery compared with po delivery, which correlates with the observed survival rate of 100%. CONCLUSIONS: In addition to being a potent lead, this work substantiates substituted diphenyl ethers as a platform for the development of novel broad-spectrum chemotherapeutics to other bacterial agents in addition to F. tularensis.

Paediatric oropharyngeal tularaemia requiring surgical intervention.

Tularaemia is a rare infectious disease endemic in most European countries caused by the bacterium Francisella tularensis 1 Patients often show acute non-specific symptoms, which causes a delay in diagnosis and proper treatment, potentially resulting in significant morbidities such as deep neck abscess, meningitis, endocarditis and septic shock. The authors present a case of a 5-year old boy with a 4-day history of fever, sore throat and painful cervical lymphadenopathy, whose clinical progression worsened despite being treated with recommended antibiotics as per WHO guidelines once the diagnosis of Tularaemia was confirmed by serologic tests. He developed a parapharyngeal abscess and a persistent left necrotic cervical lymph node, which both were surgically drained and excised, respectively, and an extended course of antibiotic was given. Subsequently, the patient fully recovered from the illness and the follow-up was negative for relapse.

Francisella tularensis subsp. tularensis Schu S4 disulfide bond formation protein B, but not an RND-type efflux pump, is required for virulence.

Francisella tularensis subsp. tularensis is a highly virulent bacterium that is a CDC select agent. Despite advancements in the understanding of its biology, details pertaining to virulence are poorly understood. In previous work, we identified a transposon insertion mutant in the FTT0107c locus that was defective in intracellular survival in HepG2 and J77A.1 cells. Here, we report that this mutant was also highly attenuated in vivo. The FTT0107c locus is predicted to encode an ortholog of the disulfide bond formation B protein (DsbB). This designation was confirmed by complementation of an Escherichia coli dsbB mutant. This dsbB mutant of Schu S4 was highly attenuated in mice, but unlike what has been reported for Francisella novicida, intranasal immunization with a sublethal dose did not induce protection against wild-type challenge. dsbB was found to be transcribed in an operon with acrA and acrB, which encode an RND-type efflux pump. However, this pump did not make a significant contribution to virulence because strains with nonpolar deletions in acrA and acrB behaved like wild-type strain Schu S4 with respect to intracellular growth and in vivo virulence. This result is in contrast to a report that an acrB mutant of a live vaccine strain of F. tularensis has decreased virulence in mice. Overall, these results demonstrate key differences between the virulence requirements of Schu S4 and less virulent subspecies of Francisella. We have shown that DsbB is a key participant in intracellular growth and virulence, and our results suggest that there are critical virulence factors that contain disulfide bonds.

Initial delay in the immune response to Francisella tularensis is followed by hypercytokinemia characteristic of severe sepsis and correlating with upregulation and release of damage-associated molecular patterns.

"Francisella tularensis subsp. novicida" intranasal infection causes a rapid pneumonia in mice with mortality at 4 to 6 days with a low dose of bacteria (10(2) bacteria). The short time to death suggests that there is a failure of the innate immune response. As the neutrophil is often the first cell type to infiltrate sites of infection, we focused on the emigration of neutrophils in this infection, as well as cytokines involved in their recruitment. The results indicated that there was a significant delay in the influx of neutrophils into the bronchoalveolar lavage fluid of F. tularensis subsp. novicida-infected mice. The delay in neutrophil recruitment in F. tularensis subsp. novicida-infected mice correlated with a delay in the upregulation of multiple proinflammatory cytokines and chemokines, as well as a delay in caspase-1 activation. Strikingly, the initial delay in the upregulation of cytokines through 1 day postinfection was followed by profound upregulation of multiple cytokines and chemokines to levels consistent with hypercytokinemia described for severe sepsis. This finding was further supported by a bacteremia and the cellular relocalization and release of high-mobility group box-1 and S100A9, both of which are damage-associated molecular pattern molecules and are known to be mediators of severe sepsis.

Type IV pili in Francisella tularensis: roles of pilF and pilT in fiber assembly, host cell adherence, and virulence.

Francisella tularensis, a highly virulent facultative intracellular bacterium, is the causative agent of tularemia. Genome sequencing of all F. tularensis subspecies revealed the presence of genes that could encode type IV pili (Tfp). The live vaccine strain (LVS) expresses surface fibers resembling Tfp, but it was not established whether these fibers were indeed Tfp encoded by the pil genes. We show here that deletion of the pilF putative Tfp assembly ATPase in the LVS resulted in a complete loss of surface fibers. Disruption of the pilT putative disassembly ATPase also caused a complete loss of pili, indicating that pilT functions differently in F. tularensis than in model Tfp systems such as those found in Pseudomonas aeruginosa and Neisseria spp. The LVS pilF and pilT mutants were attenuated for virulence in a mouse model of tularemia by the intradermal route. Furthermore, although absence of pili had no effect on the ability of the LVS to replicate intracellularly, the pilF and pilT mutants were defective for adherence to macrophages, pneumocytes, and hepatocytes. This work confirms that the surface fibers expressed by the LVS are encoded by the pil genes and provides evidence that the Francisella pili contribute to host cell adhesion and virulence.

Outbreak of tularemia: a case-control study and environmental investigation in Turkey.

OBJECTIVE: The aim of this study was to identify the potential factors associated with infection sources and modes of transmission during a recent outbreak (October 2004) of tularemia in Suluova, Turkey. METHODS: Following the diagnosis of five patients with tularemia in October 2004, active surveillance was initiated to identify further cases. This was a matched case-control study with analysis based on the first 43 cases of tularemia (probable or suspected) and 43 matched controls. A probable case was defined as a patient, resident in Suluova, who had signs and symptoms (regional lymphadenopathy and fever) compatible with tularemia and a positive serology or PCR for Francisella tularensis during the period October 21 to November 31, 2004. A suspected case was defined as a patient with compatible signs and symptoms who did not meet the laboratory criteria for a probable case, who also had no laboratory evidence of infection by other microorganisms, and who was resident in Suluova between the same dates. The microagglutination test was used for serological diagnosis. A standardized questionnaire was used to collect information on general demographics, exposure to all known sources of tularemia infection, potential risk factors related to water and animals (i.e., fishing, farming, hunting, and other activities), and the environmental conditions of the house. PCR was used to screen for evidence of the tularemia agents in clinical samples from patients and water samples. RESULTS: The overall attack rate was 2.3 per 1000 population (86/38000). Twenty-eight suspected cases and 15 probable cases of tularemia were included in the study. The most common presenting symptom was lymphadenopathy present in 95.3%, followed by fever (83.7%) and sore throat (79.1%). Twenty-eight out of 43 were reported to have painful lymph nodes. F. tularensis was detected by PCR in samples obtained from the ulcerated lesions of two patients. In the multivariate logistic regression model, keeping a domestic animal in the garden was associated with an increased risk of contracting the disease (OR=10.87; 95% CI: 1.26-93.65; p=0.03). F. tularensis was detected by PCR in the water sample obtained from the rivulet that passes through Suluova. CONCLUSIONS: The results of this study show that case-control studies may be useful for analyzing epidemics and for identifying the source of infection. In order to prevent water-related zoonotic infections, water and sewerage systems should be improved.

The Cynomolgus Macaque Natural History Model of Pneumonic Tularemia for Predicting Clinical Efficacy Under the Animal Rule.

Francisella tularensis is a highly infectious Gram-negative bacterium that is the etiologic agent of tularemia in animals and humans and a Tier 1 select agent. The natural incidence of pneumonic tularemia worldwide is very low; therefore, it is not feasible to conduct clinical efficacy testing of tularemia medical countermeasures (MCM) in human populations. Development and licensure of tularemia therapeutics and vaccines need to occur under the Food and Drug Administration's (FDA's) Animal Rule under which efficacy studies are conducted in well-characterized animal models that reflect the pathophysiology of human disease. The Tularemia Animal Model Qualification (AMQ) Working Group is seeking qualification of the cynomolgus macaque (Macaca fascicularis) model of pneumonic tularemia under Drug Development Tools Qualification Programs with the FDA based upon the results of studies described in this manuscript. Analysis of data on survival, average time to death, average time to fever onset, average interval between fever and death, and bacteremia; together with summaries of clinical signs, necropsy findings, and histopathology from the animals exposed to aerosolized F. tularensis Schu S4 in five natural history studies and one antibiotic efficacy study form the basis for the proposed cynomolgus macaque model. Results support the conclusion that signs of pneumonic tularemia in cynomolgus macaques exposed to 300-3,000 colony forming units (cfu) aerosolized F. tularensis Schu S4, under the conditions described herein, and human pneumonic tularemia cases are highly similar. Animal age, weight, and sex of animals challenged with 300-3,000 cfu Schu S4 did not impact fever onset in studies described herein. This study summarizes critical parameters and endpoints of a well-characterized cynomolgus macaque model of pneumonic tularemia and demonstrates this model is appropriate for qualification, and for testing efficacy of tularemia therapeutics under Animal Rule.

Ocular Manifestations of Mosquito-Transmitted Diseases.

Of the 3,548 known mosquito species, about 100 transmit human diseases. Mosquitoes are distributed globally throughout tropical and temperate regions where standing water sources are available for egg laying and the maturation of larva. Female mosquitoes require blood meals for egg production. This is the main pathway for disease transmission. Mosquitoes carry several pathogenic organisms responsible for significant ocular pathology and vision loss including West Nile, Rift Valley, chikungunya, dengue viruses, various encephalitis viruses, malarial parasites, Francisella tularensis, microfilarial parasites, including Dirofilaria, Wuchereria, and Brugia spp., and human botfly larvae. Health care providers may not be familiar with many of these mosquito-transmitted diseases or their associated ocular findings delaying diagnosis, treatment, and recovery of visual function. This article aims to provide an overview of the ocular manifestations associated with mosquito-transmitted diseases.

New approaches to diagnosis and therapy of tularemia.

Francisella tularensis is a potent pathogen and a cause of severe human disease. The outcome of tularemia will depend on rapid insertion of appropriate antibiotics. Until recently, effective clinical handling was hampered by shortcomings in laboratory diagnostics. No suitable direct methods were available and, because of risks and isolate recovery difficulties associated with laboratory work, culture has been rarely practiced. Due to achievements from work on modern technology, however, tularemia can now be rapidly and specifically diagnosed. Conventional PCR has been successfully applied on wound specimens of patients acquiring tularemia, and prospects for application on other human specimens are promising. Besides allowing diagnostics at high sensitivity and specificity, the PCR technology will also facilitate the identification of cases of tularemia presenting with aberrant signs and symptoms. Antibiotics for efficacious treatment of tularemia have been available for several decades. Although highly valuable, these drugs are afflicted with adverse effects and/or are available only for parenteral therapy. Recently, quinolones have been shown to afford a new valuable option for treatment of tularemia caused by F. tularensis subsp. holarctica (type B). Experience in treating more severe disease caused by F. tularensis subsp. tularensis (type A) is currently limited. In essence, the clinical handling of tularemia is currently facilitated by new achievements in molecular diagnostics and, at least with regard to type B tularemia, by the introduction of quinolones for therapy.

Mucosal immunopathogenesis of Francisella tularensis.

Respiratory infection with Francisella tularensis is the deadliest form of disease and represents the most likely route to be used by bioterrorists. Although mucosal surfaces represent the first line of defense against respiratory tularemia, and in fact, against the great majority of human pathogens, little is known about protective immunity at these sites. The objective of this chapter is to review recent data examining the importance of various pulmonary immune mechanisms in defense against F. tularensis infection and to evaluate potential strategies for induction of protective lung immunity. Aerosol and intranasal mouse infection models have yielded essentially equivalent results and have implicated an important role for Th1-type immune responses in protection, including IFN-gamma, TNF-alpha, and IL-12. The cells responsible for protection in the lung are not well-characterized but NK cells are an early target for activation after infection although it appears that CD8 T cells might be most critical for host resistance. In addition, it is becoming increasingly clear that antibodies can provide prophylactic and therapeutic protection against pulmonary infection but only in the presence of active cell-mediated immunity. In fact, in vitro exposure of resting macrophages to antibody-coated bacteria in the absence of IFN-gamma can actually enhance infection. Although various immune mechanisms can be shown to be important for protection against attenuated strains such as LVS, the real challenge for the future is to design efficacious approaches to prevent disease by highly virulent strains such as SchuS4.

Pneumonic tularemia on Martha's Vineyard: clinical, epidemiologic, and ecological characteristics.

Martha's Vineyard, Massachusetts, is the site of the only two recognized outbreaks of primary pneumonic tularemia in the United States. Beginning in 2000 and continuing through 2006, 59 presumed or confirmed tularemia cases have been reported from Martha's Vineyard, with more than 60% of these presumed to be due to inhalation of the agent. A joint CDC/Massachusetts Department of Public Health case-control study identified landscaping activities such as lawnmowing or brush cutting to be important risk factors. The fomites that serve as the basis for risk for landscapers, however, remain unidentified. Clinically, cases generally have a pneumonic component, but the development of pulmonary signs can be greatly delayed. The spectrum of illness ranges from relatively mild disease, in which cases may be treated on an outpatient basis, to severe illness requiring hospitalization. In each scenario, gentamicin therapy tends to rapidly induce defervescence, although exceptions have been noted. Even with heightened awareness during the current outbreak, physicians may easily miss a diagnosis of tularemia, usually by attributing illness to the more common Febrile illnesses. Dog ticks appear to maintain the agent on this island, with as many as 5% infected by the agent of tularemia. The main hosts for dog ticks, skunks and raccoons, are very frequently seroreactive, suggesting the possibility for their involvement in environmental contamination due to their peridomestic habits. Why tularemia is prevalent on Martha's Vineyard and why it commonly presents as a pneumonic disease there remain undescribed.

Tularemia: history, epidemiology, pathogen physiology, and clinical manifestations.

Francisella tularensis has been recognized as a human pathogen for almost 100 years and is the etiological agent of the zoonotic disease tularemia. Soon after its discovery, it became recognized as an important pathogen in several parts of the world, for example, in the United States and Soviet Union. The number of tularemia cases in the two countries peaked in the 1940s and has thereafter steadily declined. Despite this decline, there was still much interest in the pathogen in the 1950s and 1960s since it is highly infectious and transmissible by aerosol, rendering it a potent biothreat agent. In fact, it was one of the agents that was given the highest priority in the offensive programs of the United States and Soviet Union. After termination of the offensive programs in the 1960s, the interest in F. tularensis diminished significantly and little research was carried out for several decades. Outbreaks of tularemia during the last decade in Europe, for example, in Kosovo, Spain, and Scandinavia, led to a renewed public interest in the disease. This, together with a massive increase in the research funding, in particular in the United States since 2001, has resulted in a significant increase in the number of active Francisella researchers. This article summarizes, predominantly with a historical perspective, the epidemiology and clinical manifestations of tularemia and the physiology of F. tularensis.

A 65-Year-Old Groundskeeper With High Fever, Pulmonary Nodules, and Thoracic Lymphadenopathy.

A 65-year-old man with treated latent tuberculous infection presented with 1 week of fevers (up to 39.6°C), chills, headache, lightheadedness, and malaise. He reported a chronic, nonproductive cough without hemoptysis but denied other localizing symptoms, sick contacts, or recent travel. He lived in an urban area in eastern Colorado and owned one healthy dog but otherwise denied known animal exposures. He was a retired oil driller who had worked in southern Arizona, New Mexico, and northern Mexico (Sonora region). Other travel included 3 years in the early 1970s working as a military aircraft mechanic in Vietnam, Laos, and Thailand. Six weeks prior to admission, he began work as a groundskeeper on a golf course that had experienced recent flooding, using a riding mower and exposing himself to airborne dust and organic debris. He smoked a pipe daily for 30 years but quit 2 months prior to presentation, although he continued to smoke marijuana weekly. He denied intravenous drug use.