Identification of Francisella tularensis in ascites in the context of typhoidal tularaemia

Tularaemia is a highly infectious, zoonotic disease caused by Francisella tularensis, which has become increasingly prevalent over the past decade. Depending on the route of infection, different clinical manifestations can be observed. We report a case of typhoidal tularaemia presenting as a febrile illness with gastrointestinal symptoms in a patient in her mid-80s. During the acute illness phase and in the context of alcohol-related liver cirrhosis, the patient developed progressive ascites. During paracentesis, spontaneous bacterial peritonitis was consistently reported. Blood culture revealed Gram-negative bacilli identified as F. tularensis upon microscopic examination. Immediate clinical improvement was observed after adaptation to a pathogen-specific antibiotic regime. Typhoidal tularaemia presents general, non-specific symptoms without the local manifestations seen in other forms of the disease, thus representing a diagnostic challenge. In the case of protracted fever and if the epidemiological context as well as possible exposure are compatible, tularaemia should be considered in the differential diagnosis.

Tularemia research activity: a bibliometric analysis between 1980 and 2020

INTRODUCTION

Tularemia disease attracts attention as an important contagious zoonosis that has increased its impact in recent years. The aim of the study is to analyze the publications on tularemia between 1980 and 2020.

METHODS

We performed literature retrieval in the Web of Science (WoS) on 22 September 2021. Search terms were "Francisella tularensis" and "Tularemia" in the article title for the period between January 1980 and December 2020. We determined the number of articles, keywords, countries, authors, and institutions for each publication. We visualized the data with the VOS viewer tool.

RESULTS

After all inclusion and exclusion criteria were applied finally, 1688 articles were analyzed. The number of articles has increased in recent years. The three most productive countries in tularemia were the USA (777 articles 46.03%), Sweden (113 articles 6.69%), and Turkey (95 articles, 5.63%). Most of the articles were from the journal of Infection and Immunity (II), Plos one, Journal of Clinical Microbiology (JCM), Emerging Infectious Diseases (EID), and Vaccine. Sjostedt A. and Umea University-Sweden were the most influential author and institution.

CONCLUSIONS

Productivity trend has been shown to increase in tularemia. High-income countries had a great influence on the literature in the field. Publications from the USA were in a high percentage among all articles. Related work may lead to the future direction of this dossier in the next years.

Host Immunity and Francisella tularensis: A Review of Tularemia in Immunocompromised Patients

Tularemia, caused by the bacterium Francisella tularensis, is an infrequent zoonotic infection, well known in immunocompetent (but poorly described in immunocompromised) patients. Although there is no clear literature data about the specific characteristics of this disease in immunocompromised patients, clinical reports seem to describe a different presentation of tularemia in these patients. Moreover, atypical clinical presentations added to the fastidiousness of pathogen identification seem to be responsible for a delayed diagnosis, leading to a” loss of chance” for immunocompromised patients. In this article, we first provide an overview of the host immune responses to Francisella infections and discuss how immunosuppressive therapies or diseases can lead to a higher susceptibility to tularemia. Then, we describe the particular clinical patterns of tularemia in immunocompromised patients from the literature. We also provide hints of an alternative diagnostic strategy regarding these patients. In conclusion, tularemia should be considered in immunocompromised patients presenting pulmonary symptoms or unexplained fever. Molecular techniques on pathological tissues might improve diagnosis with faster results.

Laboratory Methods for Detection of Infectious Agents and Serological Response in Humans With Tick-Borne Infections: A Systematic Review of Evaluations Based on Clinical Patient Samples

Background: For the most important and well-known infections spread by Ixodes ticks, Lyme borreliosis (LB) and tick-borne encephalitis (TBE), there are recommendations for diagnosis and management available from several health authorities and professional medical networks. However, other tick-borne microorganisms with potential to cause human disease are less known and clear recommendations on diagnosis and management are scarce. Therefore, we performed a systematic review of published studies and reviews focusing on evaluation of laboratory methods for clinical diagnosis of human tick-borne diseases (TBDs), other than acute LB and TBE. The specific aim was to evaluate the scientific support for laboratory diagnosis of human granulocytic anaplasmosis, rickettsiosis, neoehrlichiosis, babesiosis, hard tick relapsing fever, tularemia and bartonellosis, as well as tick-borne co-infections and persistent LB in spite of recommended standard antibiotic treatment.

Methods: We performed a systematic literature search in 11 databases for research published from 2007 through 2017, and categorized potentially relevant references according to the predefined infections and study design. An expert group assessed the relevance and eligibility and reviewed the articles according to the QUADAS (diagnostic studies) or AMSTAR (systematic reviews) protocols, respectively. Clinical evaluations of one or several diagnostic tests and systematic reviews were included. Case reports, non-human studies and articles published in other languages than English were excluded.

Results: A total of 48 studies fulfilled the inclusion criteria for evaluation. The majority of these studies were based on small sample sizes. There were no eligible studies for evaluation of tick-borne co-infections or for persistent LB after antibiotic treatment.

Conclusions: Our findings highlight the need for larger evaluations of laboratory tests using clinical samples from well-defined cases taken at different time-points during the course of the diseases. Since the diseases occur at a relatively low frequency, single-center cross-sectional studies are practically not feasible, but multi-center case control studies could be a way forward.

A case of Francisella tularensis meningitis in a 64-year-old man treated with quinolones

We report a French case of tularemic meningitis - the second to be thoroughly described - and discuss the existing literature. The patient is a 64-year-old man with no medical history, who developed fever, cutaneous symptoms, and swollen lymph nodes within a week after a hunt. He was then diagnosed with meningitis caused by Francisella tularensis subsp. holarctica. Healing was quickly achieved ad integrum within 3 weeks with a course of ciprofloxacin. We discuss the existing literature about this specific issue, and try to shine a light on the superior efficacy and lesser toxicity of quinolones compared to the historical treatment.

Hypermetabolic pulmonary lesions on FDG-PET/CT: Tularemia or neoplasia?

OBJECTIVES

Pulmonary tularemia is a rare and little-known disease, whose clinical and radiological presentation can be confused with those of much more frequent pathologies, such as lung cancer or B-cell lymphoma (46,000 and 5,000 new cases respectively per year in France). Furthermore, PET/CT is a powerful tool for the diagnosis of malignancies or the exploration of fever of unknown origin. The objective of this study was to describe the characteristics of pulmonary tularemia and to determine whether its PET/CT aspect could help distinguish it from neoplasia.

METHODS

Retrospective observational study collecting all pulmonary tularemia cases for which a PET/CT was performed between 2016 and 2020.

RESULTS

Twenty-seven cases of pulmonary tularemia were analyzed. The sex ratio was 4.4, and the median age was 60 years. Clinical manifestations were mainly represented by fever (n=23), arthralgia (n=7) and cough (n=6). PET/CT revealed intensely hypermetabolic mediastinal adenopathies in all cases, associated with parenchymal (n=20) or pleural (n=6) lesions, suggesting neoplastic pathology in 15 patients. Cytopuncture or lymph node biopsy was performed in 16 patients, revealing non-specific adenitis (n=8), necrotic epithelio-gigantocellular granuloma (n=3), or were non-contributory (n=5). All patients reported significant environmental exposure. The outcome was favorable for all patients, spontaneously for 8 of them and after antibiotic therapy with either doxycycline or ciprofloxacin for the other 19.

CONCLUSIONS

Depending on the epidemiological setting, pulmonary tularemia may be considered an alternative diagnosis to lung cancer, lymphoma, or tuberculosis, in the presence of infectious symptoms and hypermetabolic pulmonary lesions and mediastinal lymphadenopathies on PET/CT.

Tularemia: A Case Series of Patients Diagnosed at the National Reference Center for Rickettsioses From 2008 to 2017

BACKGROUND

We describe the epidemiological, clinical, and prognostic aspects of 177 tularemia cases diagnosed at the National Reference Center for rickettsioses, coxiellosis, and bartonelloses between 2008 and 2017.

METHODS

All patients with a microbiological diagnosis of tularemia made in the laboratory were included. Clinical and epidemiological data were collected retrospectively from clinicians in charge of patients using a standardized questionnaire. Diagnostic methods used were indirect immunofluorescence serology, real-time polymerase chain reaction (PCR), and universal PCR targeting the 16S ribosomal ribonucleic acid gene.

RESULTS

The series included 54 females and 123 males (sex ratio, 2.28; mean age, 47.38 years). Eighty-nine (50.2%) were confirmed as having tularemia on the basis of a positive Francisella tularensis PCR or seroconversion, and 88 (49.8%) were considered as probable due to a single positive serum. The regions of France that were most affected included Pays de la Loire (22% of cases), Nouvelle Aquitaine (18.6% of cases), and Grand Est (12.4% of cases). Patients became infected mainly through contact with rodents or game (38 cases, 21.4%), through tick-bites (23 cases, 12.9%), or during outdoor leisure activities (37 cases, 20.9%). Glandular and ulceroglandular forms were the most frequent (109 cases, 61.5%). Two aortitis, an infectious endocarditis, a myocarditis, an osteoarticular infection, and a splenic hematoma were also diagnosed. Tularemia was discovered incidentally in 54.8% of cases. Seventy-eight patients were hospitalized, and no deaths were reported.

CONCLUSIONS

Our data suggest that in an endemic area and/or in certain epidemiological contexts, tularemia should be sought to allow an optimized antibiotic therapy and a faster recovery.

Optimized MALDI TOF Mass Spectrometry Identification of Francisella tularensis Subsp. holarctica

Francisella tularensis is a tier 1 agent causing the zoonosis tularemia. This highly infectious Gram-negative bacterium is occasionally isolated from human samples (especially blood samples) in routine clinical microbiology laboratories. A rapid and accurate method for identifying this pathogen is needed in order to optimize the infected patient’s healthcare management and prevent contamination of the laboratory personnel. MALDI TOF mass spectrometry has become the gold standard for the rapid identification of most human pathogens. However, F. tularensis identification using such technology and commercially available databases is currently considered unreliable. Real-time PCR-based methods for rapid detection and accurate identification of F. tularensis are not available in many laboratories. As a national reference center for tularemia, we developed a MALDI TOF database allowing accurate identification of the species F. tularensis and its differentiation from the closely related neighbor species F. tularensis subsp. novicida and F. philomiragia. The sensitivity and specificity of this database were validated by testing 71 F. tularensis strains and 165 strains from 63 species not belonging to the Francisella genus. We obtained accurate identification at the species level and differentiation of all the tested bacterial strains. In particular, F. tularensis could be accurately differentiated from other small Gram-negative bacilli occasionally isolated from human samples, including species of the HACEK group and Brucella melitensis.

Early Diagnosis of Tularemia by Flow Cytometry, Czech Republic, 2003-20151

We retrospectively assessed the utility of a flow cytometry–based test quantifying the percentage of CD3+ T cells with the CD4–/CD8– phenotype for predicting tularemia diagnoses in 64 probable and confirmed tularemia patients treated during 2003–2015 and 342 controls with tularemia-like illnesses treated during 2012–2015 in the Czech Republic. The median percentage of CD3+/CD4–/CD8– T cells in peripheral blood was higher in tularemia patients (19%, 95% CI 17%–22%) than in controls (3%, 95% CI 2%–3%). When we used 8% as the cutoff, this test’s sensitivity was 0.953 and specificity 0.895 for distinguishing cases from controls. The CD3+/CD4–/CD8– T cells increased a median of 7 days before tularemia serologic test results became positive. This test supports early presumptive diagnosis of tularemia for clinically suspected cases 7–14 days before diagnosis can be confirmed by serologic testing in regions with low prevalences of tularemia-like illnesses.

Pulmonary tularaemia: a differential diagnosis to lung cancer

Background

Pulmonary manifestations of tularaemia are reported to be infrequent in previous publications. During 2016, we noticed an increase in the number of hospitalised patients with pulmonary tularaemia in Eastern Norway. We aimed to investigate primary pulmonary tularaemia in Eastern Norway in terms of symptoms, radiological and microbiological findings, incidence and risk exposure.

Methods

A retrospective analysis of consecutive primary pulmonary tularaemia cases from 2016 until 2018 was conducted.

Results

From 1 September, 2016 until 31 December, 2018, 22 patients were diagnosed with primary pulmonary tularaemia at Innlandet Hospital Trust, representing 48% of all reported tularaemia cases in the region. A peak annual incidence of 3.4 in 100 000 was found in 2017.

All 22 patients lived in, or had recently visited, rural areas. Eighteen patients reported risk exposure for tularaemia, such as wood chopping, outdoor activities and farming prior to symptom onset. All patients experienced fever, and 19 patients had respiratory symptoms. Ten patients were in spontaneous recovery at diagnosis.

All patients had a chest computed tomography scan. Overall, 19 patients had pulmonary lesions and 18 had enlarged intrathoracic lymph nodes. The computed tomography images were described as suspicious of malignancy in 17 patients.

Conclusion

Pulmonary manifestations in tularaemia occurred more frequently in our region than expected from previous reports. Although all patients had symptoms consistent with infection, the majority were primarily investigated considering lung cancer due to the radiology report. In endemic areas, pulmonary tularaemia may be an important differential diagnosis to lung cancer.

Pulmonary tularaemia is possibly more frequent than previously reported. Due to similar radiological findings, pulmonary tularaemia may be an important differential diagnosis to lung cancer in endemic areas.https://bit.ly/2RcEPfN

Ecology of Francisella tularensis

Tularemia is a Holarctic zoonosis caused by the gamma proteobacterium Francisella tularensis and is considered to be a vector-borne disease. In many regions, human risk is associated with the bites of flies, mosquitoes, or ticks. But the biology of the agent is such that risk may be fomite related, and large outbreaks can occur due to inhalation or ingestion of contaminated materials. Such well-documented human risk factors suggest a role for these risk factors in the enzootic cycle as well. Many arthropods support the growth or survival of the agent, but whether arthropods (ticks in particular) are obligately required for the perpetuation of F. tularensis remains to be demonstrated. As with most zoonoses, our knowledge of the ecology of F. tularensis has been driven with the objective of understanding human risk. In this review, we focus on the role of the arthropod in maintaining F. tularensis, particularly with respect to long-term enzootic persistence.

Antibiotic susceptibility of Francisella tularensis subsp. holarctica strains isolated from tularaemia patients in France between 2006 and 2016

Objectives

To determine the in vitro susceptibility to 18 antibiotics of human strains of Francisella tularensis isolated in France between 2006 and 2016, to check the absence of acquired resistance and to evaluate potential therapeutic alternatives.

Methods

Fifty-nine clinically unrelated F. tularensis subsp. holarctica strains identified at the French National Reference Centre for Francisella as belonging to the phylogenetic subclade B.FTNF002-00 were used. MICs were determined in CAMHB medium supplemented with 2% PolyViteX®, using the CLSI broth microdilution method.

Results

All strains were susceptible to fluoroquinolones (ofloxacin, ciprofloxacin, levofloxacin and moxifloxacin; MIC range: 0.016-0.25 mg/L), aminoglycosides (gentamicin and tobramycin; MIC range: ≤0.03-0.25 mg/L), doxycycline (MIC range: 0.125-0.25 mg/L) and chloramphenicol (MIC range: 0.5-2 mg/L). The erythromycin MIC range (0.5-2 mg/L) confirmed that all isolates belonged to biovar I of F. tularensis subsp. holarctica. Azithromycin and telithromycin displayed lower MIC ranges (0.25-1 and 0.03-0.5 mg/L, respectively). The tigecycline MIC range (0.25-1 mg/L) was slightly higher than that of doxycycline. All strains were resistant to ampicillin, meropenem, daptomycin, clindamycin and linezolid.

Conclusions

F. tularensis strains isolated in France remain susceptible to antibiotic classes recommended for tularaemia treatment. Because fluoroquinolones display the lowest MIC90, have bactericidal activity and have lower therapeutic failure rates compared with doxycycline, they may be advocated as first-line treatment of mild cases of tularaemia, predominant in Europe. MIC data also indicate that azithromycin or telithromycin may be possible therapeutic options against biovar I strains from Western Europe in case of contraindication to first-line antibiotics.

Severe infections due to Francisella tularensis ssp. holarctica in solid organ transplant recipient: report of two cases and review of literature

Background

Tularemia is a rare zoonotic infection caused by bacterium Francisella tularensis. It has been well described in immunocompetent patients but poorly described in immunocompromised patients notably in solid organ transplant recipients.

Case presentations

We report here two cases of tularemia in solid organ transplant recipients including first case after heart transplant. We also carried out an exhaustive review of literature describing characteristics of this infection in solid organ transplant recipients.

Tularemia: an experience of 13 cases including a rare myocarditis in a referral center in Eastern Switzerland (Central Europe) and a review of the literature

BACKGROUND

Tularemia, a zoonotic disease caused by Francisella tularensis, can cause a broad spectrum of disease in humans including six major clinical presentations: the ulceroglandular, glandular, oculoglandular, oropharyngeal, typhoidal and pneumonic form. The epidemiology and ecology and thus transmission of tularemia are complex, depending on conditions unique to specific locations.

CASE SERIES AND METHODS

Thirteen cases with different forms of the disease and one very rare case of a myocarditis are reported, discussed, and reviewed within the scope of current literature.

CONCLUSION

Tularemia is a rare, but emerging disease in Central Europe with glandular and ulceroglandular disease as its predominant forms. Transmission is mainly caused by contact with lagomorphs, rodents and tick bites. However, domestic cats may play an important role in transmission too. Myocarditis is probably a worldwide, but very rare manifestation of tularemia.

Usefulness of a single-assay chemiluminescence test (Tularaemia VIRCLIA IgG + IgM monotest) for the diagnosis of human tularemia. Comparison of five serological tests

The aim of this work was to ascertain the usefulness of a new commercially-available single-assay chemiluminescence test (CHT) for the diagnosis of human tularemia (Tularaemia VIRCLIA IgG + IgM monotest, Vircell, Santa Fe, Granada, Spain). A total of 773 sera from 773 patients including 364 initial sera from patients with diagnosed tularemia, patients with suspected tularemia not confirmed (100), healthy people (152), patients with serology positive to Brucella (97), patients diagnosed with other infectious diseases (30), and patients diagnosed with autoimmune diseases (30) were included. All sera were tested by CHT, "in-house" microagglutination test (MAT), immunochromatographic test (ICT) (Virapid Tularaemia, Vircell, Santa Fe Granada, Spain), and "in-house" ELISA IgG, and ELISA IgM. Of the total initial sera, 334 (sensitivity 91.8%) were positive in the CHT, 332 (sensitivity 91.2%) in the MAT, 330 (sensitivity 90.7%) in the ICT, and 328 (sensitivity 90.1%) in the ELISA IgG and ELISA IgM tests. The specificity of the CHT was 96.7%; of the MAT, 100%; of the ICT, 98.7%; and of the ELISA IgG and ELISA IgM, 97.4%. In the group of patients with serology positive to Brucella, at least 12.4% of sera were positive in tularemia tests (12.4% in ELISA IgM, 13.4% in MAT, 14.4% in ICT, and 15.5% in CHT and ELISA IgG). In conclusion, CHT presents a sensitivity and specificity in early diagnosis of human tularemia, similar to MAT, ICT, and ELISA IgG and ELISA IgM. Its single assay design allows lower costs, especially in areas of low endemicity or inter-epidemic periods.

Evaluation of In-House and Commercial Serological Tests for Diagnosis of Human Tularemia

Tularemia is a zoonosis caused by the bacterium Francisella tularensis Its specific diagnosis remains based on serological methods, while F. tularensis is rarely detected in clinical samples by culture or PCR. The aim of the present study was to evaluate the performance of the Serion enzyme-linked immunosorbent assay (ELISA) classic Francisella tularensis IgG and IgM tests (Virion/Serion GmbH Institute, Würzburg, Germany) and the VIRapid tularemia immunochromatographic test (ICT) (Vircell, Granada, Spain) compared to that of the in-house microagglutination test (MAT) and indirect immunofluorescence assay (IFA) currently used at the French National Reference Center for Francisella We evaluated 256 consecutive sera from 208 patients, including 51 confirmed and 23 probable tularemia cases, and 134 control patients not infected with F. tularensis The IFA tests displayed 72.5% sensitivity for IgM (cutoff titer ≥80) and 74.5% for IgG (cutoff titer ≥160), and 99.3% specificity for both IgM and IgG. Using cutoffs advocated by the manufacturer, the Serion ELISAs displayed 88.2% sensitivity for IgM and 86.3% for IgG antibodies; specificity was 94.8% for IgM and 95.5% for IgG. Compared to MAT and IFA tests, the Serion ELISAs allowed earlier detection of specific antibodies (1 to 2 weeks versus 2 to 3 weeks after the onset of symptoms). The ICT sensitivity and specificity were 90% and 83.6%, respectively, when considering the cutoff advocated by the manufacturer. In conclusion, the Serion ELISAs are useful as screening tests for tularemia diagnosis, but additional confirmatory tests (such as MAT and IFA) are needed, especially in areas of low endemicity.

Francisella tularensis and other bacteria in hares and ticks in North Rhine-Westphalia (Germany)

Tularemia is a zoonotic disease caused by the bacterium Francisella tularensis. The disease can be transmitted to humans through contact with infected animals such as the European brown hare (Lepus europaeus) and ticks as vectors. The aim of this study was to isolate F. tularensis from ticks and hares in North Rhine-Westphalia using cysteine heart agar to determine their genetic relatedness and to identify other bacteria that grow on this medium. 848 European brown hares and 1556 questing ticks (all Ixodes ricinus) from forests were tested using cultivation and MALDI-TOF mass spectrometry or partial 16S rRNA gene sequencing. The majority of F. tularensis isolates from hares (n=24; 96%) and genomic F. tularensis DNA recovered from ticks belonged to the basal genetic clade IV and subclade B.18. These isolates were sensitive to erythromycin and were assigned to biovar I. Only a single strain isolated from a hare was assigned to basal clade I (B.12/B.35). All isolates were sensitive to tetracycline, doxycycline, streptomycin, gentamicin, chloramphenicol, and ciprofloxacin. Only 4 tick pools were positive for F. tularensis and cultivation was not successful in any of the pools. Most of the other isolated bacteria belonged to the order Bacillales with 36 Staphylococcus isolates, 9 Bacillus isolates and 8 Paenibacillus isolates. Prominent members of Enterobacterales were represented by different genera like Pantoea, Erwinia, Raoultella etc. Several of the bacterial species were soil or plant-associated, but some of the bacterial species were found in I. ricinus for the first time. Our results showed that F. tularensis was detected only in few ticks of an endemic area, but ticks were also infected by several other bacteria with zoonotic potential. Therefore, a wider spectrum of pathogens should be considered if a patient was bitten by a tick.

In vitro and in vivo evaluation of fluoroquinolone resistance associated with DNA gyrase mutations in Francisella tularensis, including in tularaemia patients with treatment failure

Fluoroquinolones (FQs) are highly effective for treating tularaemia, a zoonosis caused by Francisella tularensis, but failures and relapses remain common in patients with treatment delay or immunocompromised status. FQ-resistant strains of F. tularensis harboring mutations in the quinolone-resistance determining region (QRDR) of gyrA and gyrB, the genes encoding subunits A and B of DNA gyrase, have been selected in vitro. Such mutants have never been isolated from humans as this microorganism is difficult to culture. In this study, the presence of FQ-resistant mutants of F. tularensis was assessed in tularaemia patients using combined culture- and PCR-based approaches. We analyzed 42 F. tularensis strains and 82 tissue samples collected from 104 tularaemia cases, including 32 (30.7%) with FQ treatment failure or relapse. Forty F. tularensis strains and 55 clinical samples were obtained before any FQ treatment, while 2 strains and 15 tissue samples were collected after treatment. FQ resistance was evaluated by the minimum inhibitory concentration (MIC) for the bacterial strains, and by newly developed PCR-based methods targeting the gyrA and gyrB QRDRs for both the bacterial strains and the clinical samples. None of the F. tularensis strains displayed an increased MIC compared with FQ-susceptible controls. Neither gyrA nor gyrB QRDR mutation was found in bacterial strains and tissue samples tested, including those from patients with FQ treatment failure or relapse. Further phenotypic and genetic resistance traits should be explored to explain the poor clinical response to FQ treatment in such tularaemia patients.

Francisella tularensis prevalence and load in Dermacentor reticulatus ticks in an endemic area in Central Europe

A total of 7778 host-seeking adult Dermacentor reticulatus (Ixodida: Ixodidae) ticks were examined for the prevalence of Francisella tularensis holarctica (Thiotrichales: Francisellaceae) in a natural focus of tularaemia in the floodplain forest-meadow ecosystem along the lower reaches of the Dyje (Thaya) river in South Moravia (Czech Republic) between 1995 and 2013. Ticks were pooled (10 specimens per pool) and their homogenates inoculated subcutaneously in 4-week-old specific pathogen-free mice. Dead mice were sectioned, their spleens cultivated on thioglycollate-glucose-blood agar and impression smears from the spleen, liver and heart blood were Giemsa-stained. Sixty-four pools were positive for F. tularensis: the overall minimum infection rate (MIR) was 0.82%. Overall MIRs for the 4714 female and 3064 male D. reticulatus examined were 0.89 and 0.72%, respectively; MIRs fluctuated across years between 0.0 and 2.43%. The estimated bacterial load in infected ticks varied from 0.84 to 5.34 log₁₀ infectious F. tularensis cells per tick (i.e. from about seven to 220 000 cells). Ticks with low loads were more prevalent; more than 1000 infectious cells were detected in 24 ticks (0.3% of all ticks and 37.5% of infected ticks). Monitoring of D. reticulatus for the presence and cell numbers of F. tularensis may be a valuable tool in the surveillance of tularaemia.

Seroprevalence of seven pathogens transmitted by the Ixodes ricinus tick in forestry workers in France

In order to assess the level of occupational exposure to the main pathogens transmitted by the Ixodes ricinus tick, a seroprevalence study was performed on serum samples collected in 2003 from 2975 forestry workers of northeastern France. The global seroprevalence estimated for the seven pathogens studied was 14.1% (419/2975) for Borrelia burgdorferi sl, 5.7% (164/2908) for Francisella tularensis, 2.3% (68/2941) for tick-borne encephalitis virus, 1.7% (50/2908) for Anaplasma phagocytophilum and 1.7% (48/2908) for Bartonella henselae. The seroprevalences of Babesia divergens and Babesia microti studied in a subgroup of participants seropositive for at least one of these latter pathogens were 0.1% (1/810) and 2.5% (20/810), respectively. Borrelia burgdorferi sl seroprevalence was significantly higher in Alsace and Lorraine and F. tularensis seroprevalence was significantly higher in Champagne-Ardenne and Franche-Comté. The results of this survey also suggest low rates of transmission of Bartonella henselae and F. tularensis by ticks and a different west/east distribution of Babesia species in France. The frequency and potential severity of these diseases justify continued promotion of methods of prevention of I. ricinus bites.

Molecular mechanisms underlying the emergence of bacterial pathogens: an ecological perspective

The rapid emergence of new bacterial diseases negatively affects both human health and agricultural productivity. Although the molecular mechanisms underlying these disease emergences are shared between human- and plant-pathogenic bacteria, not much effort has been made to date to understand disease emergences caused by plant-pathogenic bacteria. In particular, there is a paucity of information in the literature on the role of environmental habitats in which plant-pathogenic bacteria evolve and on the stress factors to which these microbes are unceasingly exposed. In this microreview, we focus on three molecular mechanisms underlying pathogenicity in bacteria, namely mutations, genomic rearrangements and the acquisition of new DNA sequences through horizontal gene transfer (HGT). We briefly discuss the role of these mechanisms in bacterial disease emergence and elucidate how the environment can influence the occurrence and regulation of these molecular mechanisms by directly impacting disease emergence. The understanding of such molecular evolutionary mechanisms and their environmental drivers will represent an important step towards predicting bacterial disease emergence and developing sustainable management strategies for crops.

Evolutionary Insights into IL17A in Lagomorphs

In leporids, IL17A had been implicated in the host defense against extracellular pathogens, such as Francisella tularensis that infects hares and rabbits and causes the zoonotic disease tularemia. Here, we studied IL17A from five lagomorphs, European rabbit, pygmy rabbit, brush rabbit, European brown hare, and American pika. We observed that this protein is highly conserved between these species, with a similarity of 97-99% in leporids and ~88% between leporids and American pika. The exon/intron structure, N-glycosylation sites, and cysteine residues are conserved between lagomorphs. However, at codon 88, one of the interaction sites between IL17A and its receptor IL17RA, there is an Arg>Pro mutation that only occurs in European rabbit and European brown hare. This could induce critical alterations in the IL17A structure and conformation and consequently modify its function. The differences observed between leporids and humans or rodents might also represent important alterations in protein structure and function. In addition, as for other interleukins, IL17A sequences of human and European rabbit are more closely related than the sequences of human and mouse or European rabbit and mouse. This study gives further support to the hypothesis that European rabbit might be a more suitable animal model for studies on human IL17.

A rapid real-time quantitative PCR assay to determine the minimal inhibitory extracellular concentration of antibiotics against an intracellular Francisella tularensis Live Vaccine Strain

Francisella tularensis is a highly virulent facultative intracellular bacterium. The lack of a safe and efficient vaccine makes antibiotics the preferred treatment. F. tularensis antibiotic susceptibility tests are based on the in vitro standard CLSI-approved microdilution method for determining the MIC. However, limited data are available regarding the minimal inhibitory extracellular concentration (MIEC) needed to eradicate intracellular bacteria. Here, we evaluated the MIEC values of various WHO-recommended antibiotics and compared the MIEC values to the established MICs. We describe a rapid 3-h quantitative PCR (qPCR) intracellular antibiogram assay, which yields comparable MIEC values to those obtained by the classical 72-h cfu assay. This rapid qPCR assay is highly advantageous in light of the slow growth rates of F. tularensis. Our results showed that the MIECs obtained for doxycycline, chloramphenicol and ciprofloxacin were indicative of intracellular activity. Gentamicin was not effective against intracellular bacteria for at least 32 h post treatment, raising the question of whether slow-penetrating gentamicin should be used for certain stages of the disease. We suggest that the qPCR intracellular antibiogram assay may be used to screen for potentially active antibiotics against intracellular F. tularensis as well as to detect strains with acquired resistance to recommended antibiotics.

Predicting tularemia with clinical, laboratory and demographical findings in the ED

INTRODUCTION

We aimed to determine clinical, laboratory and demographical characteristics of tularemia on admission to Emergency Department (ED).

MATERIAL AND METHODS

Medical data of 317 patients admitted to ED and subsequently hospitalized with suspected tularemia between January 1, 2011, and May 31, 2015, were collected. Patients were divided into 2 groups according to microagglutination test results, as tularemia (+) and tularemia (-).

RESULTS

Of the 317 patients involved, 49 were found to be tularemia (+) and 268 were tularemia (-). Mean age of the tularemia (+) patients was found to be higher than that of tularemia (-) patients. When compared to tularemia (-) patients, a significant portion of patients in tularemia (+) patients were elderly, living in rural areas and had contact with rodents. When clinical and laboratory findings of the 2 groups were compared, any statistical significance could not be determined.

CONCLUSION

Tularemia is a disease of elderly people living in rural areas. Contact with rodents also increases risk of tularemia in suspected patients.

Francisella tularensis aortitis

Francisella tularensis, the agent of tularemia, is a Gram-negative coccobacillus primarily pathogen for animals and occasionally for humans. The clinical manifestations of tularemia include pneumonia, ulceroglandular, oropharyngeal, or typhoidal disease. Rare manifestations are also described, but to our knowledge, we describe here the first case of F. tularensis aortitis in a human. Diagnosis was confirmed by the presence of F. tularensis in blood culture, by the presence of F. tularensis DNA in the aortic biopsy and by specific IgG and IgM responses against the bacteria. The outcome was favorable after surgery and specific antimicrobial therapy.

The status of tularemia in Europe in a one-health context: a review

The bacterium Francisella tularensis causes the vector-borne zoonotic disease tularemia, and may infect a wide range of hosts including invertebrates, mammals and birds. Transmission to humans occurs through contact with infected animals or contaminated environments, or through arthropod vectors. Tularemia has a broad geographical distribution, and there is evidence which suggests local emergence or re-emergence of this disease in Europe. This review was developed to provide an update on the geographical distribution of F. tularensis in humans, wildlife, domestic animals and vector species, to identify potential public health hazards, and to characterize the epidemiology of tularemia in Europe. Information was collated on cases in humans, domestic animals and wildlife, and on reports of detection of the bacterium in arthropod vectors, from 38 European countries for the period 1992-2012. Multiple international databases on human and animal health were consulted, as well as published reports in the literature. Tularemia is a disease of complex epidemiology that is challenging to understand and therefore to control. Many aspects of this disease remain poorly understood. Better understanding is needed of the epidemiological role of animal hosts, potential vectors, mechanisms of maintenance in the different ecosystems, and routes of transmission of the disease.