scholarly journals Development, Phenotypic Characterization and Genomic Analysis of a Francisella tularensis Panel for Tularemia Vaccine Testing

2021 ◽  
Vol 12 ◽  
Author(s):  
Beth A. Bachert ◽  
Joshua B. Richardson ◽  
Kevin D. Mlynek ◽  
Christopher P. Klimko ◽  
Ronald G. Toothman ◽  
...  
Keyword(s):  
Francisella Tularensis ◽  
Genomic Analysis ◽  
Pathogenicity Island ◽  
Phenotypic Characterization ◽  
Effective Vaccine ◽  
Multiple Strains ◽  
Tularemia Vaccine ◽  
Vaccine Testing ◽  
Schu S4 ◽  
Genomic Similarity

Francisella tularensis is one of several biothreat agents for which a licensed vaccine is needed to protect against this pathogen. To aid in the development of a vaccine protective against pneumonic tularemia, we generated and characterized a panel of F. tularensis isolates that can be used as challenge strains to assess vaccine efficacy. Our panel consists of both historical and contemporary isolates derived from clinical and environmental sources, including human, tick, and rabbit isolates. Whole genome sequencing was performed to assess the genetic diversity in comparison to the reference genome F. tularensis Schu S4. Average nucleotide identity analysis showed >99% genomic similarity across the strains in our panel, and pan-genome analysis revealed a core genome of 1,707 genes, and an accessory genome of 233 genes. Three of the strains in our panel, FRAN254 (tick-derived), FRAN255 (a type B strain), and FRAN256 (a human isolate) exhibited variation from the other strains. Moreover, we identified several unique mutations within the Francisella Pathogenicity Island across multiple strains in our panel, revealing unexpected diversity in this region. Notably, FRAN031 (Scherm) completely lacked the second pathogenicity island but retained virulence in mice. In contrast, FRAN037 (Coll) was attenuated in a murine pneumonic tularemia model and had mutations in pdpB and iglA which likely led to attenuation. All of the strains, except FRAN037, retained full virulence, indicating their effectiveness as challenge strains for future vaccine testing. Overall, we provide a well-characterized panel of virulent F. tularensis strains that can be utilized in ongoing efforts to develop an effective vaccine against pneumonic tularemia to ensure protection is achieved across a range F. tularensis strains.

scholarly journals Disruption of Francisella tularensis Schu S4iglI,iglJ, andpdpCGenes Results in Attenuation for Growth in Human Macrophages andIn VivoVirulence in Mice and Reveals a Unique Phenotype forpdpC

2012 ◽  
Vol 81 (3) ◽  
pp. 850-861 ◽  
Author(s):  
Matthew E. Long ◽  
Stephen R. Lindemann ◽  
Jed A. Rasmussen ◽  
Bradley D. Jones ◽  
Lee-Ann H. Allen
Keyword(s):  
Francisella Tularensis ◽  
Bacterial Pathogen ◽  
Human Monocyte ◽  
Pathogenicity Island ◽  
Intermediate Phenotype ◽  
Small Subset ◽  
Content Type ◽  
Isolation And Characterization ◽  
Schu S4

ABSTRACTFrancisella tularensisis a facultative intracellular bacterial pathogen and the causative agent of tularemia. After infection of macrophages, the organism escapes from its phagosome and replicates to high density in the cytosol, but the bacterial factors required for these aspects of virulence are incompletely defined. Here, we describe the isolation and characterization ofFrancisella tularensissubsp.tularensisstrain Schu S4 mutants that lack functionaliglI,iglJ, orpdpC, three genes of theFrancisellapathogenicity island. Our data demonstrate that these mutants were defective for replication in primary human monocyte-derived macrophages and murine J774 cells yet exhibited two distinct phenotypes. TheiglIandiglJmutants were similar to one another, exhibited profound defects in phagosome escape and intracellular growth, and appeared to be trapped in cathepsin D-positive phagolysosomes. Conversely, thepdpCmutant avoided trafficking to lysosomes, phagosome escape was diminished but not ablated, and these organisms replicated in a small subset of infected macrophages. The phenotype of each mutant strain was reversed bytranscomplementation.In vivovirulence was assessed by intranasal infection of BALB/c mice. The mutants appeared avirulent, as all mice survived infection with 108CFUiglJ-orpdpC-deficient bacteria. Nevertheless, thepdpCmutant disseminated to the liver and spleen before being eliminated, whereas theiglJmutant did not. Taken together, our data demonstrate that the pathogenicity island genes tested are essential forF. tularensisSchu S4 virulence and further suggest thatpdpCmay play a unique role in this process, as indicated by its distinct intermediate phenotype.

scholarly journals The Early Phagosomal Stage of Francisella tularensis Determines Optimal Phagosomal Escape and Francisella Pathogenicity Island Protein Expression

2008 ◽  
Vol 76 (12) ◽  
pp. 5488-5499 ◽  
Author(s):  
Audrey Chong ◽  
Tara D. Wehrly ◽  
Vinod Nair ◽  
Elizabeth R. Fischer ◽  
Jeffrey R. Barker ◽  
...  
Keyword(s):  
Protein Expression ◽  
Francisella Tularensis ◽  
Pathogenicity Island ◽  
Endocytic Pathway ◽  
Atpase Inhibitor ◽  
Murine Bone Marrow ◽  
Concanamycin A ◽  
Late Endosomes ◽  
Endosomal Acidification ◽  
Schu S4

ABSTRACT Francisella tularensis is an intracellular pathogen that can survive and replicate within macrophages. Following phagocytosis and transient interactions with the endocytic pathway, F. tularensis rapidly escapes from its original phagosome into the macrophage cytoplasm, where it eventually replicates. To examine the importance of the nascent phagosome for the Francisella intracellular cycle, we have characterized early trafficking events of the F. tularensis subsp. tularensis strain Schu S4 in a murine bone marrow-derived macrophage model. Here we show that early phagosomes containing Schu S4 transiently interact with early and late endosomes and become acidified before the onset of phagosomal disruption. Inhibition of endosomal acidification with the vacuolar ATPase inhibitor bafilomycin A1 or concanamycin A prior to infection significantly delayed but did not block phagosomal escape and cytosolic replication, indicating that maturation of the early Francisella-containing phagosome (FCP) is important for optimal phagosomal escape and subsequent intracellular growth. Further, Francisella pathogenicity island (FPI) protein expression was induced during early intracellular trafficking events. Although inhibition of endosomal acidification mimicked the early phagosomal escape defects caused by mutation of the FPI-encoded IglCD proteins, it did not inhibit the intracellular induction of FPI proteins, demonstrating that this response is independent of phagosomal pH. Altogether, these results demonstrate that early phagosomal maturation is required for optimal phagosomal escape and that the early FCP provides cues other than intravacuolar pH that determine intracellular induction of FPI proteins.

scholarly journals Yellow Fever Outbreak in Eastern Senegal, 2020–2021

Viruses ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1475
Author(s):  
Moussa Moïse Diagne ◽  
Marie Henriette Dior Ndione ◽  
Alioune Gaye ◽  
Mamadou Aliou Barry ◽  
Diawo Diallo ◽  
...  
Keyword(s):  
Yellow Fever ◽  
Yellow Fever Virus ◽  
Mosquito Species ◽  
Virus Transmission ◽  
Genomic Analysis ◽  
Hemorrhagic Fever ◽  
Fever Virus ◽  
World Health ◽  
Effective Vaccine ◽  
Ministry Of Health

Yellow fever virus remains a major threat in low resource countries in South America and Africa despite the existence of an effective vaccine. In Senegal and particularly in the eastern part of the country, periodic sylvatic circulation has been demonstrated with varying degrees of impact on populations in perpetual renewal. We report an outbreak that occurred from October 2020 to February 2021 in eastern Senegal, notified and managed through the synergistic effort yellow fever national surveillance implemented by the Senegalese Ministry of Health in collaboration with the World Health Organization, the countrywide 4S network set up by the Ministry of Health, the Institut Pasteur de Dakar, and the surveillance of arboviruses and hemorrhagic fever viruses in human and vector populations implemented since mid 2020 in eastern Senegal. Virological analyses highlighted the implication of sylvatic mosquito species in virus transmission. Genomic analysis showed a close relationship between the circulating strain in eastern Senegal, 2020, and another one from the West African lineage previously detected and sequenced two years ago from an unvaccinated Dutch traveler who visited the Gambia and Senegal before developing signs after returning to Europe. Moreover, genome analysis identified a 6-nucleotide deletion in the variable domain of the 3′UTR with potential impact on the biology of the viral strain that merits further investigations. Integrated surveillance of yellow fever virus but also of other arboviruses of public health interest is crucial in an ecosystem such as eastern Senegal.

scholarly journals Molecular Epidemiology of Antimicrobial-Resistant Commensal Escherichia coli Strains in a Cohort of Newborn Calves

2005 ◽  
Vol 71 (11) ◽  
pp. 6680-6688 ◽  
Author(s):  
Deborah V. Hoyle ◽  
Catherine M. Yates ◽  
Margo E. Chase-Topping ◽  
Esther J. Turner ◽  
Sarah E. Davies ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Turning Point ◽  
Temporal Trends ◽  
Resistant Isolate ◽  
Phenotypic Characterization ◽  
Environmental Source ◽  
Newborn Calves ◽  
Resistant Strains ◽  
Multiple Strains ◽  
Common Combination

ABSTRACT Pulsed-field gel electrophoresis (PFGE) was used to investigate the dissemination and diversity of ampicillin-resistant (Ampr) and nalidixic acid-resistant (Nalr) commensal Escherichia coli strains in a cohort of 48 newborn calves. Calves were sampled weekly from birth for up to 21 weeks and a single resistant isolate selected from positive samples for genotyping and further phenotypic characterization. The Ampr population showed the greatest diversity, with a total of 56 different genotype patterns identified, of which 5 predominated, while the Nalr population appeared to be largely clonal, with over 97% of isolates belonging to just two different PFGE patterns. Distinct temporal trends were identified in the distribution of several Ampr genotypes across the cohort, with certain patterns predominating at different points in the study. Cumulative recognition of new Ampr genotypes within the cohort was biphasic, with a turning point coinciding with the housing of the cohort midway through the study, suggesting that colonizing strains were from an environmental source on the farm. Multiply resistant isolates dominated the collection, with >95% of isolates showing resistance to at least two additional antimicrobials. Carriage of resistance to streptomycin, sulfamethoxazole, and tetracycline was the most common combination, found across several different genotypes, suggesting the possible spread of a common resistance element across multiple strains. The proportion of Ampr isolates carrying sulfamethoxazole resistance increased significantly over the study period (P < 0.05), coinciding with a decline in the most common genotype pattern. These data indicate that calves were colonized by a succession of multiply resistant strains, with a probable environmental source, that disseminated through the cohort over time.

scholarly journals Genome-Wide Identification of Francisella tularensis Virulence Determinants

2007 ◽  
Vol 75 (6) ◽  
pp. 3089-3101 ◽  
Author(s):  
Jingliang Su ◽  
Jun Yang ◽  
Daimin Zhao ◽  
Thomas H. Kawula ◽  
Jeffrey A. Banas ◽  
...  
Keyword(s):  
Francisella Tularensis ◽  
Stress Responses ◽  
Small Subset ◽  
Virulence Determinants ◽  
Genome Wide ◽  
Genes Encoding ◽  
Capsule Locus ◽  
Life Threatening ◽  
Transposon Mutants ◽  
Schu S4

ABSTRACT Francisella tularensis is a gram-negative pathogen that causes life-threatening infections in humans and has potential for use as a biological weapon. The genetic basis of the F. tularensis virulence is poorly understood. This study screened a total of 3,936 transposon mutants of the live vaccine strain for infection in a mouse model of respiratory tularemia by signature-tagged mutagenesis. We identified 341 mutants attenuated for infection in the lungs. The transposon disruptions were mapped to 95 different genes, virtually all of which are also present in the genomes of other F. tularensis strains, including human pathogenic F. tularensis strain Schu S4. A small subset of these attenuated mutants carried insertions in the genes encoding previously known virulence factors, but the majority of the identified genes have not been previously linked to F. tularensis virulence. Among these are genes encoding putative membrane proteins, proteins associated with stress responses, metabolic proteins, transporter proteins, and proteins with unknown functions. Several attenuated mutants contained disruptions in a putative capsule locus which partially resembles the poly-γ-glutamate capsule biosynthesis locus of Bacillus anthracis, the anthrax agent. Deletional mutation analysis confirmed that this locus is essential for F. tularensis virulence.

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