The phylogeographic pattern of Francisella tularensis in Sweden indicates a Scandinavian origin of Eurosiberian tularaemia.

Previous studies of the causative agent of tularaemia, Francisella tularensis have identified phylogeographic patterns suggestive of environmental maintenance reservoirs. To investigate the phylogeography of tularaemia in Sweden, we selected 163 clinical isolates obtained during 1995-2009 in 10 counties and sequenced one isolate's genome to identify new genetic markers. An improved typing scheme based on two indels and nine SNPs was developed using hydrolysis or TaqMan MGB probe assays. The results showed that much of the known global genetic diversity of F. tularensis subsp. holarctica is present in Sweden. Thirteen of the 163 isolates belonged to a new genetic group that is basal to all other known members of the major genetic clade B.I, which is spread across the Eurosiberian region. One hundred and twenty-five of the 163 Swedish isolates belonged to B.I, but individual clades' frequencies differed from county to county (P < 0.001). Subsequent analyses revealed a correlation between genotype variation over time and recurrent outbreaks at specific places, supporting the 'maintenance reservoir' environmental maintenance hypothesis. Most importantly, the findings reveal the presence of diverse source populations of F. tularensis subsp. holarctica in Sweden and suggest a historical spread of the disease from Scandinavia to other parts of Eurosiberia.

Genome sequence of Francisella tularensis subspecies holarctica strain FSC200, isolated from a child with tularemia.

Here we report the complete, accurate 1.89-Mb genome sequence of Francisella tularensis subsp. holarctica strain FSC200, isolated in 1998 in the Swedish municipality Ljusdal, which is in an area where tularemia is highly endemic. This genome is important because strain FSC200 has been extensively used for functional and genetic studies of Francisella and is well-characterized.

Proteomic Signatures of Antimicrobial Resistance in Yersinia pestis and Francisella tularensis.

Antimicrobial resistance (AMR) is a well-recognized, widespread, and growing issue of concern. With increasing incidence of AMR, the ability to respond quickly to infection with or exposure to an AMR pathogen is critical. Approaches that could accurately and more quickly identify whether a pathogen is AMR also are needed to more rapidly respond to existing and emerging biological threats. We examined proteins associated with paired AMR and antimicrobial susceptible (AMS) strains of Yersinia pestis and Francisella tularensis, causative agents of the diseases plague and tularemia, respectively, to identify whether potential existed to use proteins as signatures of AMR. We found that protein expression was significantly impacted by AMR status. Antimicrobial resistance-conferring proteins were expressed even in the absence of antibiotics in growth media, and the abundance of 10-20% of cellular proteins beyond those that directly confer AMR also were significantly changed in both Y. pestis and F. tularensis. Most strikingly, the abundance of proteins involved in specific metabolic pathways and biological functions was altered in all AMR strains examined, independent of species, resistance mechanism, and affected cellular antimicrobial target. We have identified features that distinguish between AMR and AMS strains, including a subset of features shared across species with different resistance mechanisms, which suggest shared biological signatures of resistance. These features could form the basis of novel approaches to identify AMR phenotypes in unknown strains.

Complete Genome Sequence of Francisella halioticida Type Strain DSM 23729 (FSC1005).

Here, we announce the complete genome sequence of the Francisella halioticida type strain DSM 23729 (FSC1005), isolated from a diseased cultured giant abalone in Japan in 2005. The genome is composed of a 2,197,430-bp-long circular chromosome, with a G+C content of 31.2%.

Network Experiences from a Cross-Sector Biosafety Level-3 Laboratory Collaboration: A Swedish Forum for Biopreparedness Diagnostics.

The Swedish Forum for Biopreparedness Diagnostics (FBD) is a network that fosters collaboration among the 4 agencies with responsibility for the laboratory diagnostics of high-consequence pathogens, covering animal health and feed safety, food safety, public health and biodefense, and security. The aim of the network is to strengthen capabilities and capacities for diagnostics at the national biosafety level-3 (BSL-3) laboratories to improve Sweden's biopreparedness, in line with recommendations from the EU and WHO. Since forming in 2007, the FBD network has contributed to the harmonization of diagnostic methods, equipment, quality assurance protocols, and biosafety practices among the national BSL-3 laboratories. Lessons learned from the network include: (1) conducting joint projects with activities such as method development and validation, ring trials, exercises, and audits has helped to build trust and improve communication among participating agencies; (2) rotating the presidency of the network steering committee has fostered trust and commitment from all agencies involved; and (3) planning for the implementation of project outcomes is important to maintain gained competencies in the agencies over time. Contacts have now been established with national agencies of the other Nordic countries, with an aim to expanding the collaboration, broadening the network, finding synergies in new areas, strengthening the ability to share resources, and consolidating long-term financing in the context of harmonized European biopreparedness.

Introduction and persistence of tularemia in Bulgaria.

INTRODUCTION: Outbreaks of the zoonotic disease tularemia occurred in north-east Bulgaria in the 1960s. Then came 30 years of epidemiological silence until new outbreaks occurred in west Bulgaria in the 1990s. To investigate how bacterial strains of Francisella tularensis causing tularemia in wildlife and humans in the 1960s and the 1990s were related, we explored their genetic diversity. MATERIAL AND METHODS: Ten F. tularensis genomes from the 1960s (n=3) and the 1990s (n=7) were sequenced, assigned to canonical single-nucleotide polymorphism (canSNP) clades, and compared to reference genomes. We developed four new canSNP polymerase chain reaction (PCR) assays based on the genome sequence information. RESULTS AND DISCUSSION: The genetic analysis showed that the outbreaks in the 1960s as well as in the 1990s involved multiple clones and new genetic diversity. The smallest genetic difference found between any of the Bulgarian strains was five SNPs between the strains L2 and 81 isolated 43 years apart, indicating that F. tularensis may persist locally over long time periods without causing outbreaks. The existence of genetically highly similar strain-pairs isolated the same year in the same area from different hosts supports a hypothesis of local expansion of clones during outbreaks. Close relationship (two SNPs) was found between one strain isolated 1961 in northeast Bulgaria and one strain isolated 5 years before in USSR. Historical data coinciding with the actual time point describe the introduction of water rats from USSR into the Bulgarian outbreak area, which may explain the close genetic relationship and the origin of the outbreak. CONCLUSION: Genome analysis of strains from two outbreaks in the 1960s and the 1990s provided valuable information on the genetic diversity and persistence of F. tularensis in Bulgaria.

Complete Genome Sequence of Francisella guangzhouensis Strain 08HL01032T, Isolated from Air-Conditioning Systems in China.

We present the complete genome sequence of Francisella guangzhouensis strain 08HL01032(T), which consists of one chromosome (1,658,482 bp) and one plasmid (3,045 bp) with G+C contents of 32.0% and 28.7%, respectively.

Intron-mediated expression of the human neuropeptide Y Y1 receptor.

The Neuropeptide Y (NPY) family of neuropeptides exert their function through a family of heptahelical G-protein coupled receptors regulating essential physiological processes. A 97 base pair intron (intron IV) intervenes the coding sequence of the human NPY Y1 receptor (hY1) gene and was found frequently retained at variable levels in poly A+ mRNA isolated from multiple human tissues. When included in hY1 expression vectors, either in its natural position or 5' of the hY1 cDNA, intron IV mediated a significant increase of both hY1 mRNA and corresponding functional receptor protein in transfected mammalian cells, implying an in vivo regulatory function of the endogenous intron. Our results further indicate that the nuclear history of the hY1 pre-mRNA influence ectopic hY1 production through post-transcriptional mechanisms and argues against intron IV acting as a transcriptional enhancer as well as the possibility that a putative hY1 related 5TM accessory protein encoded by the non-spliced hY1 mRNA would facilitate hY1 production on a post-translational level.

Increases in melanin-concentrating hormone and MCH receptor levels in the hypothalamus of dietary-obese rats.

Melanin-concentrating hormone (MCH) is a hypothalamic neuropeptide that stimulates feeding and increases body weight in rodents. We studied the role of the system in energy homeostasis and its regulation by the satiety signals, leptin and insulin. We used real-time PCR to measure the hypothalamic expression of MCH and its receptor (MCHR1) in two contrasting models of altered nutritional status, namely, obesity induced by 8 weeks' voluntary overeating and food restriction for 10 days. Diet-fed rats were stratified according to final total fat-pad mass into a 'high fat gain' group (HG) and 'low fat gain' group (LG). MCH mRNA levels were increased by 31% (p>0.05) and 49% (p<0.05) in the LG and HG, respectively, compared with controls. MCHR1 mRNA levels rose by 118% in the LG (p<0.01) and 85% in the HG (p<0.01). There were significant positive correlations (p<0.05) between plasma leptin concentration and both MCH and MCHR1 mRNA levels, and between plasma insulin and MCHR1 expression. A positive correlation was also observed between MCH and MCHR1 mRNA levels (p<0.05). Food-restricted rats showed no significant alterations in the levels of either MCH mRNA or MCHR1 mRNA. In a second experiment, we measured MCH peptide levels in five discrete hypothalamic areas of dietary-obese rats. MCH concentrations were significantly increased in the arcuate nuclei of the HG (p<0.05) and the paraventricular nuclei of both the LG (p<0.05) and HG (p<0.05), compared with their lean counterparts. These results suggest that the MCH system becomes more active in dietary obesity and could be involved in enhancing appetite for palatable food. The possibility that MCH and MCHR1 expression are positively regulated by leptin and insulin, which normally inhibit feeding, is a putative explanation for how appetite for palatable food is able to override mechanisms that prevent the development of obesity.

Recombinant HpaA purified from Escherichia coli has biological properties similar to those of native Helicobacter pylori HpaA.

The aim of this study was to recombinantly produce and purify Helicobacter pylori adhesin A (HpaA) from Escherichia coli and compare it to purified native H. pylori HpaA, for potential use as a vaccine antigen. The hpaA gene was cloned from H. pylori, transferred to two different expression vectors, and transformed into E. coli. Expression of rHpaA was analysed by immunoblot, inhibition ELISA, and semi-quantitative dot-blot. Using affinity chromatography, rHpaA was purified from E. coli and native HpaA from H. pylori. The binding of both purified proteins to sialic acid was analysed and antibody titres to native and rHpaA were compared after intraperitoneal immunisation of C57/Bl mice. The rHpaA protein was highly expressed in E. coli from both vectors. Purified recombinant and native HpaA bound similarly to fetuin but also to the non-sialylated asialofetuin. Both native HpaA and rHpaA induced comparable amounts of specific antibodies in serum after immunisation and they were identical in double immunodiffusion. In conclusion, rHpaA was successfully produced in E. coli. Purified rHpaA showed biological properties similar to those of native HpaA isolated from H. pylori and may therefore be further used as an antigen in the development of a vaccine against H. pylori infection.

Genome sequence of Coxiella burnetii strain Namibia.

We present the whole genome sequence and annotation of the Coxiella burnetii strain Namibia. This strain was isolated from an aborting goat in 1991 in Windhoek, Namibia. The plasmid type QpRS was confirmed in our work. Further genomic typing placed the strain into a unique genomic group. The genome sequence is 2,101,438 bp long and contains 1,979 protein-coding and 51 RNA genes, including one rRNA operon. To overcome the poor yield from cell culture systems, an additional DNA enrichment with whole genome amplification (WGA) methods was applied. We describe a bioinformatics pipeline for improved genome assembly including several filters with a special focus on WGA characteristics.

Eight new genomes and synthetic controls increase the accessibility of rapid melt-MAMA SNP typing of Coxiella burnetii.

The case rate of Q fever in Europe has increased dramatically in recent years, mainly because of an epidemic in the Netherlands in 2009. Consequently, there is a need for more extensive genetic characterization of the disease agent Coxiella burnetii in order to better understand the epidemiology and spread of this disease. Genome reference data are essential for this purpose, but only thirteen genome sequences are currently available. Current methods for typing C. burnetii are criticized for having problems in comparing results across laboratories, require the use of genomic control DNA, and/or rely on markers in highly variable regions. We developed in this work a method for single nucleotide polymorphism (SNP) typing of C. burnetii isolates and tissue samples based on new assays targeting ten phylogenetically stable synonymous canonical SNPs (canSNPs). These canSNPs represent previously known phylogenetic branches and were here identified from sequence comparisons of twenty-one C. burnetii genomes, eight of which were sequenced in this work. Importantly, synthetic control templates were developed, to make the method useful to laboratories lacking genomic control DNA. An analysis of twenty-one C. burnetii genomes confirmed that the species exhibits high sequence identity. Most of its SNPs (7,493/7,559 shared by >1 genome) follow a clonal inheritance pattern and are therefore stable phylogenetic typing markers. The assays were validated using twenty-six genetically diverse C. burnetii isolates and three tissue samples from small ruminants infected during the epidemic in the Netherlands. Each sample was assigned to a clade. Synthetic controls (vector and PCR amplified) gave identical results compared to the corresponding genomic controls and are viable alternatives to genomic DNA. The results from the described method indicate that it could be useful for cheap and rapid disease source tracking at non-specialized laboratories, which requires accurate genotyping, assay accessibility and inter-laboratory comparisons.

Direct repeat-mediated deletion of a type IV pilin gene results in major virulence attenuation of Francisella tularensis.

Francisella tularensis, the causative agent of tularaemia, is a highly infectious and virulent intracellular pathogen. There are two main human pathogenic subspecies, Francisella tularensis ssp. tularensis (type A), and Francisella tularensis ssp. holarctica (type B). So far, knowledge regarding key virulence determinants is limited but it is clear that intracellular survival and multiplication is one major virulence strategy of Francisella. In addition, genome sequencing has revealed the presence of genes encoding type IV pili (Tfp). One genomic region encoding three proteins with signatures typical for type IV pilins contained two 120 bp direct repeats. Here we establish that repeat-mediated loss of one of the putative pilin genes in a type B strain results in severe virulence attenuation in mice infected by subcutaneous route. Complementation of the mutant by introduction of the pilin gene in cis resulted in complete restoration of virulence. The level of attenuation was similar to that of the live vaccine strain and this strain was also found to lack the pilin gene as result of a similar deletion event mediated by the direct repeats. Presence of the pilin had no major effect on the ability to interact, survive and multiply inside macrophage-like cell lines. Importantly, the pilin-negative strain was impaired in its ability to spread from the initial site of infection to the spleen. Our findings indicate that this putative pilin is critical for Francisella infections that occur via peripheral routes.

Lack of in vitro and in vivo recognition of Francisella tularensis subspecies lipopolysaccharide by Toll-like receptors.

Francisella tularensis is an intracellular gram-negative bacterium that is highly infectious and potentially lethal. Several subspecies exist of varying pathogenicity. Infection by only a few organisms is sufficient to cause disease depending on the model system. Lipopolysaccharide (LPS) of gram-negative bacteria is generally recognized by Toll-like receptor 4 (TLR4)/MD-2 and induces a strong proinflammatory response. Examination of human clinical F. tularensis isolates revealed that human virulent type A and type B strains produced lipid A of similar structure to the nonhuman model pathogen of mice, Francisella novicida. F. novicida LPS or lipid A is neither stimulatory nor an antagonist for human and murine cells through TLR4 or TLR2. It does not appear to interact with TLR4 or MD-2, as it is not an antagonist to other stimulatory LPS. Consistent with these observations, aerosolization of F. novicida LPS or whole bacteria induced no inflammatory response in mice. These results suggest that poor innate recognition of F. tularensis allows the bacterium to evade early recognition by the host innate immune system to promote its pathogenesis for mammals.

Evolution of subspecies of Francisella tularensis.

Analysis of unidirectional genomic deletion events and single nucleotide variations suggested that the four subspecies of Francisella tularensis have evolved by vertical descent. The analysis indicated an evolutionary scenario where the highly virulent F. tularensis subsp. tularensis (type A) appeared before the less virulent F. tularensis subsp. holarctica (type B). Compared to their virulent progenitors, attenuated strains of F. tularensis exhibited specific unidirectional gene losses.

Tularemia in Denmark: identification of a Francisella tularensis subsp. holarctica strain by real-time PCR and high-resolution typing by multiple-locus variable-number tandem repeat analysis.

We report ulceroglandular tularemia affecting an 8-year-old boy and the first recovery of Francisella tularensis in Denmark. A novel real-time PCR assay was used to identify the strain as F. tularensis subsp. holarctica (type B). Multiple-locus variable-number tandem repeat analysis demonstrated a close genetic relationship to strains from Norway.

A mutant of Francisella tularensis strain SCHU S4 lacking the ability to express a 58-kilodalton protein is attenuated for virulence and is an effective live vaccine.

Francisella tularensis subsp. tularensis (type A) strain SCHU S4 is a prototypic strain of the pathogen that is highly virulent for humans and other mammals. Its intradermal (i.d.) 50% lethal dose (LD50) for mice is <10 CFU. We discovered a spontaneous mutant, designated FSC043, of SCHU S4 with an i.d. LD50 of >10(8) CFU. FSC043 effectively vaccinated mice against challenge with a highly virulent type A strain, and the protective efficacy was at least as good as that of F. tularensis LVS, an empirically attenuated strain which has been used as an efficacious human vaccine. Comparative proteomics was used to identify two proteins of unknown function that were identified as defective in LVS and FSC043, and deletion mutants of SCHU S4 were created for each of the two encoding genes. One mutant, the DeltaFTT0918 strain, failed to express a 58-kDa protein, had an i.d. LD50 of approximately 10(5) CFU, and was found to be less capable than SCHU S4 of growing in peritoneal mouse macrophages. Mice that recovered from sublethal infection with the DeltaFTT0918 mutant survived when challenged 2 months later with >100 LD50s of the highly virulent type A strain FSC033. This is the first report of the generation of defined mutants of F. tularensis subsp. tularensis and their use as live vaccines.

Worldwide genetic relationships among Francisella tularensis isolates determined by multiple-locus variable-number tandem repeat analysis.

The intracellular bacterium Francisella tularensis is the causative agent of tularemia and poses a serious threat as an agent of bioterrorism. We have developed a highly effective molecular subtyping system from 25 variable-number tandem repeat (VNTR) loci. In our study, multiple-locus VNTR analysis (MLVA) was used to analyze genetic relationships and potential population structure within a global collection of 192 F. tularensis isolates, including representatives from each of the four subspecies. The VNTR loci displayed between 2 and 31 alleles with Nei's diversity values between 0.05 and 0.95. Neighbor-joining cluster analysis of VNTR data revealed 120 genotypes among the 192 F. tularensis isolates, including accurate subspecies identification. F. tularensis subsp. tularensis (type A) isolates showed great diversity at VNTR loci, while F. tularensis subsp. holarctica (type B) isolates showed much lower levels despite a much broader geographical prevalence. The resolution of two distinct clades within F. tularensis subsp. tularensis (designated A.I and A.II) revealed a previously unrecognized genetic division within this highly virulent subspecies. F. tularensis subsp. holarctica appears to have recently spread globally across continents from a single origin, while F. tularensis subsp. tularensis has a long and complex evolutionary history almost exclusively in North America. The sole non-North American type A isolates (Slovakian) were closely related to the SCHU S4 strain. Significant linkage disequilibrium was detected among VNTR loci of F. tularensis consistent with a clonal population structure. Overall, this work greatly augments the study of tularemia ecology and epidemiology, while providing a framework for future forensic analysis of F. tularensis isolates.

Genome-wide DNA microarray analysis of Francisella tularensis strains demonstrates extensive genetic conservation within the species but identifies regions that are unique to the highly virulent F. tularensis subsp. tularensis.

Francisella tularensis is a potent pathogen and a possible bioterrorism agent. Little is known, however, to explain the molecular basis for its virulence and the distinct differences in virulence found between the four recognized subspecies, F. tularensis subsp. tularensis, F. tularensis subsp. mediasiatica, F. tularensis subsp. holarctica, and F. tularensis subsp. novicida. We developed a DNA microarray based on 1,832 clones from a shotgun library used for sequencing of the highly virulent strain F. tularensis subsp. tularensis Schu S4. This allowed a genome-wide analysis of 27 strains representing all four subspecies. Overall, the microarray analysis confirmed a limited genetic variation within the species F. tularensis, and when the strains were compared, at most 3.7% of the probes showed differential hybridization. Cluster analysis of the hybridization data revealed that the causative agents of type A and type B tularemia, i.e., F. tularensis subsp. tularensis and F. tularensis subsp. holarctica, respectively, formed distinct clusters. Despite marked differences in their virulence and geographical origin, a high degree of genomic similarity between strains of F. tularensis subsp. tularensis and F. tularensis subsp. mediasiatica was apparent. Strains from Japan clustered separately, as did strains of F. tularensis subsp. novicida. Eight regions of difference (RD) 0.6 to 11.5 kb in size, altogether comprising 21 open reading frames, were identified that distinguished strains of the moderately virulent subspecies F. tularensis subsp. holarctica and the highly virulent subspecies F. tularensis subsp. tularensis. One of these regions, RD1, allowed for the first time the development of an F. tularensis-specific PCR assay that discriminates each of the four subspecies.