Presence of Francisella tularensis subsp. holarctica DNA in the Aquatic Environment in France

Brunet, Camille D.; Hennebique, Aurélie; Peyroux, Julien; Pelloux, Isabelle; Caspar, Yvan; Maurin, Max

doi:10.3390/microorganisms9071398

Cited by 11 publications

(6 citation statements)

References 37 publications

(96 reference statements)

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“…Notably, in 2021, pneumonic tularemia accounted for 25% of cases (Figure 3C), which can result from inhalation of contaminated aerosols or when other forms of tularemia are untreated, and the bacteria can spread through the bloodstream. This rise of pneumonic tularemia can also be observed in neighboring countries like France (21% of cases in 2018 vs. 10% in previous years; Brunet et al, 2021). It is possible that the increased numbers can be attributed to more people spending leisure time and vacations in Swiss natural environments, particularly during the COVID-19 pandemic.…”

Section: Tularemia In Switzerlandmentioning

confidence: 81%

Phylogeography of Francisella tularensis subspecies holarctica and epidemiology of tularemia in Switzerland

et al. 2023

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Tularemia, an endemic disease that mainly affects wild animals and humans, is caused by Francisella tularensis subsp. holarctica (Fth) in Switzerland. The Swiss Fth population consist of multiple different subclades which are distributed throughout the country. The aim of this study is to characterize the genetic diversity of Fth in Switzerland and to describe the phylogeographic relationship of isolates by single nucleotide polymorphism (SNP) analysis. This analysis is combined with human surveillance data from reported cases over the last 10 years and in vitro and in silico antibiotic resistance tests to provide insight into the epidemiology of tularemia in Switzerland. We sequenced the whole genomes of 52 Fth strains of human or tick origin collected in Switzerland between 2009 and 2022 and analyzed together with all publicly available sequencing data of Swiss and European Fth. Next, we performed a preliminary classification with the established canonical single nucleotide polymorphism nomenclature. Furthermore, we tested 20 isolates from all main Swiss clades for antimicrobial susceptibility against a panel of antimicrobial agents. All 52 sequenced isolates from Switzerland belong to major clade B.6, specifically subclades B.45 and B.46, previously described in Western Europe. We were able to accurately reconstruct the population structure according to the global phylogenetic framework. No resistance to clinically recommended antibiotics could be identified in vitro or in silico in the western B.6 strains.

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Section: Tularemia In Switzerlandmentioning

confidence: 81%

Phylogeography of Francisella tularensis subspecies holarctica and epidemiology of tularemia in Switzerland

et al. 2023

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“…The clinical samples picked human blood. Considering that F. tularensis will spread in aerosol form and can survive in water and soil environments (Telford and Goethert, 2020 ; Brunet et al, 2021 ; Golovliov et al, 2021 ), we finally decided to use sludge mixed with natural water to prepare sewage samples.…”

Section: Resultsmentioning

confidence: 99%

Development and evaluation of a rapid RPA/CRISPR-based detection of Francisella tularensis

Kang

Yuan

et al. 2022

Front. Microbiol.

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Francisella tularensis is a dangerous pathogen that causes an extremely contagious zoonosis in humans named tularemia. Given its low-dose morbidity, the potential to be fatal, and aerosol spread, it is regarded as a severe threat to public health. The US Centers for Disease Control and Prevention (CDC) has classified it as a category A potential agent for bioterrorism and a Tier 1 Select Agent. Herein, we combined recombinase polymerase amplification (RPA) with CRISPR/Cas12a system to select the F. tularensis target gene (TUL4), creating a two-pronged rapid and ultrasensitive diagnostic method for detecting F. tularensis. The real-time RPA (RT-RPA) assay detected F. tularensis within 10 min at a sensitivity of 5 copies/reaction, F. tularensis genomic DNA of 5 fg, and F. tularensis of 2 × 102 CFU/ml; the RPA-CRISPR/Cas12a assay detects F. tularensis within 40 min at a sensitivity of 0.5 copies/reaction, F. tularensis genomic DNA of 1 fg, and F. tularensis of 2 CFU/ml. Furthermore, the evaluation of specificity showed that both assays were highly specific to F. tularensis. More importantly, in a test of prepared simulated blood and sewage samples, the RT-RPA assay results were consistent with RT-PCR assay results, and the RPA-CRISPR/Cas12a assay could detect a minute amount of F. tularensis genomic DNA (2.5 fg). There was no nonspecific detection with blood samples and sewage samples, giving the tests a high practical application value. For example, in on-site and epidemic areas, the RT-RPA was used for rapid screening and the RPA-CRISPR/Cas12a assay was used for more accurate diagnosis.

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“…What if Fth had rather evolved to adapt to an aquatic niche yet poorly characterized so far while becoming infectious for various mammal species, which are usually dead ends for the bacteria because it often kills its hosts [3]? Indeed, this bacterium has been identified in many aquatic areas, including the sea water, rivers, ponds [25][26][27][28]39,40], which might suggest that the primary reservoir of the subspecies holarctica could rather be the aquatic environment itself. This hypothesis could explain why a specific reservoir within the environment has not been identified despite decades of research.…”

Section: Discussionmentioning

confidence: 99%

“…Therefore, it appears that conditions that are too harmful to Fth and associated with a loss of their culturability in one week do not allow the development of VBNC bacteria. The most favorable conditions for Fth survival are close to environmental conditions in tularemia endemic areas, i.e., areas of water temperatures ranging from 4 to 20°C between winter and summer periods [4,28]. Importantly after the switch into VBNC state, Fth viability was still dependent on the temperature of the water.…”

Section: Discussionmentioning

confidence: 99%

“…Although the presence and potential survival of Fth in the aquatic environment have been identified in several studies [25][26][27][28][29], the mechanisms of its persistence and its precise environmental reservoir remain unclear. According to current descriptions of the aquatic cycle of Fth, aquatic environments may be initially contaminated by F. tularensis through dead animals or excrements of infected animals [3].…”

Section: Discussionmentioning

confidence: 99%

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Aquatic long-term persistence ofFrancisella tularensisssp.holarcticais driven by water temperature and transition to a viable but non-culturable state

Brunet

Peyroux

Ponderand

et al. 2022

Preprint

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Francisella tularensis is a highly virulent bacterium causing tularemia zoonosis. An increasing proportion of infections occur through contaminated hydro-telluric sources, especially for the subspecies holarctica (Fth). Although this bacterium has been detected in several aquatic environments, the mechanisms of its long-term persistence in water are not yet elucidated. We evaluated the culturability and the viability of a virulent Fth strain in independent microcosms filled with nutrient-poor water. At 37°C, the bacteria remained culturable for only one week, while culturability was extended to 6 weeks at 18°C and up to 11 weeks at 4°C. However, while the viability of the bacteria declined similarly to culturability at 37°C, the viability of the bacteria remained stable overtime at 18°C and 4°C for more than 24 months, long after loss of culturability. We identified water temperature as one of the major factors driving the aquatic survival of Fth through a transition of the whole Fth population in a viable but non-culturable (VBNC) state. Low temperature of water (4 and 18°C) favors the persistence of the bacteria in a VBNC state, while a temperature above 30°C kills culturable and VBNC Fth bacteria. These findings provide new insights into the environmental cycle of Francisella tularensis that suggest that the yet unidentified primary reservoir of the subspecies holarctica may be the aquatic environment itself in which the bacteria could persist for months or years without the need for a host.

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Presence of Francisella tularensis subsp. holarctica DNA in the Aquatic Environment in France

Cited by 11 publications

References 37 publications

Phylogeography of Francisella tularensis subspecies holarctica and epidemiology of tularemia in Switzerland

Phylogeography of Francisella tularensis subspecies holarctica and epidemiology of tularemia in Switzerland

Development and evaluation of a rapid RPA/CRISPR-based detection of Francisella tularensis

Aquatic long-term persistence ofFrancisella tularensisssp.holarcticais driven by water temperature and transition to a viable but non-culturable state

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