The genome of Coxiella burnetii Z3055, a clone linked to the Netherlands Q fever outbreaks, provides evidence for the role of drift in the emergence of epidemic clones

Molecular detection and MST genotyping of Coxiella burnetii in ruminants and stray dogs and cats in Northern Algeria

Aiming at identifying the reservoir and contamination sources of Coxiella burnetii in Northern Algeria, we investigated the molecular presence of the bacterium in 599 samples (blood, placenta, liver, spleen, and uterus) collected from cattle, sheep, dogs and cats. Our qPCR results showed that 15/344 (4.36%) blood samples and six/255 (2.35%) organ specimens were positive for C. burnetii. In cattle, three (4%) blood and liver samples were positive. In sheep, one blood (1.19%) and 3 (8.57%) placenta samples were positive. At the Algiers dog pound, 8 (10%) and 3 (5%) blood samples were qPCR positivein dogs and cats, respectively. In addition, MST genotyping showed that MST 33 was present in cattle and sheep, MST 20 in cattle,andMST 21 in dogs and cats.

Interdisciplinary studies on Coxiella burnetii: From molecular to cellular, to host, to one health research

The Q-GAPS (Q fever GermAn interdisciplinary Program for reSearch) consortium was launched in 2017 as a German consortium of more than 20 scientists with exceptional expertise, competence, and substantial knowledge in the field of the Q fever pathogen Coxiella (C.) burnetii. C. burnetii exemplifies as a zoonotic pathogen the challenges of zoonotic disease control and prophylaxis in human, animal, and environmental settings in a One Health approach. An interdisciplinary approach to studying the pathogen is essential to address unresolved questions about the epidemiology, immunology, pathogenesis, surveillance, and control of C. burnetii. In more than five years, Q-GAPS has provided new insights into pathogenicity and interaction with host defense mechanisms. The consortium has also investigated vaccine efficacy and application in animal reservoirs and identified expanded phenotypic and genotypic characteristics of C. burnetii and their epidemiological significance. In addition, conceptual principles for controlling, surveilling, and preventing zoonotic Q fever infections were developed and prepared for specific target groups. All findings have been continuously integrated into a Web-based, interactive, freely accessible knowledge and information platform (www.q-gaps.de), which also contains Q fever guidelines to support public health institutions in controlling and preventing Q fever. In this review, we will summarize our results and show an example of how an interdisciplinary consortium provides knowledge and better tools to control a zoonotic pathogen at the national level.

Identification and Characterization of an HtrA Sheddase Produced by Coxiella burnetii

Having previously shown that soluble E-cadherin (sE-cad) is found in sera of Q fever patients and that infection of BeWo cells by C. burnetii leads to modulation of the E-cad/β-cat pathway, our purpose was to identify which sheddase(s) might catalyze the cleavage of E-cad. Here, we searched for a direct mechanism of cleavage initiated by the bacterium itself, assuming the possible synthesis of a sheddase encoded in the genome of C. burnetii or an indirect mechanism based on the activation of a human sheddase. Using a straightforward bioinformatics approach to scan the complete genomes of four laboratory strains of C. burnetii, we demonstrate that C. burnetii encodes a 451 amino acid sheddase (CbHtrA) belonging to the HtrA family that is differently expressed according to the bacterial virulence. An artificial CbHtrA gene (CoxbHtrA) was expressed, and the CoxbHtrA recombinant protein was found to have sheddase activity. We also found evidence that the C. burnetii infection triggers an over-induction of the human HuHtrA gene expression. Finally, we demonstrate that cleavage of E-cad by CoxbHtrA on macrophages-THP-1 cells leads to an M2 polarization of the target cells and the induction of their secretion of IL-10, which "disarms" the target cells and improves C. burnetii replication. Taken together, these results demonstrate that the genome of C. burnetii encodes a functional HtrA sheddase and establishes a link between the HtrA sheddase-induced cleavage of E-cad, the M2 polarization of the target cells and their secretion of IL-10, and the intracellular replication of C. burnetii.

Pangenomic analysis of Coxiella burnetii unveils new traits in genome architecture

Coxiella burnetii is the etiological agent of Q fever, a worldwide zoonosis able to cause large outbreaks. The disease is polymorphic. Symptomatic primary infection is named acute Q fever and is associated with hepatitis, pneumonia, fever, and auto-immune complications while persistent focalized infections, mainly endocarditis, and vascular infections, occur in a minority of patients but are potentially lethal. In order to evaluate the genomic features, genetic diversity, evolution, as well as genetic determinants of antibiotic resistance, pathogenicity, and ability to cause outbreaks of Q fever, we performed a pangenomic analysis and genomic comparison of 75 C. burnetii strains including 63 newly sequenced genomes. Our analysis demonstrated that C. burnetii has an open pangenome, unique genes being found in many strains. In addition, pathogenicity islands were detected in all genomes. In consequence C. burnetii has a high genomic plasticity, higher than that of other intracellular bacteria. The core- and pan-genomes are made of 1,211 and 4,501 genes, respectively (ratio 0.27). The core gene-based phylogenetic analysis matched that obtained from multi-spacer typing and the distribution of plasmid types. Genomic characteristics were associated to clinical and epidemiological features. Some genotypes were associated to specific clinical forms and countries. MST1 genotype strains were associated to acute Q fever. A significant association was also found between clinical forms and plasmids. Strains harboring the QpRS plasmid were never found in acute Q fever and were only associated to persistent focalized infections. The QpDV and QpH1 plasmids were associated to acute Q fever. In addition, the Guyanese strain CB175, the most virulent strain to date, exhibited a unique MST genotype, a distinct COG profile and an important variation in gene number that may explain its unique pathogenesis. Therefore, strain-specific factors play an important role in determining the epidemiological and clinical manifestations of Q fever alongside with host-specific factors (valvular and vascular defects notably).

Proteome-wide analysis of Coxiella burnetii for conserved T-cell epitopes with presentation across multiple host species

Background

Coxiella burnetii is the Gram-negative bacterium responsible for Q fever in humans and coxiellosis in domesticated agricultural animals. Previous vaccination efforts with whole cell inactivated bacteria or surface isolated proteins confer protection but can produce a reactogenic immune responses. Thereby a protective vaccine that does not cause aberrant immune reactions is required. The critical role of T-cell immunity in control of C. burnetii has been made clear, since either CD8⁺ or CD4⁺ T cells can empower clearance. The purpose of this study was to identify C. burnetii proteins bearing epitopes that interact with major histocompatibility complexes (MHC) from multiple host species (human, mouse, and cattle).

Results

Of the annotated 1815 proteins from the Nine Mile Phase I (RSA 493) assembly, 402 proteins were removed from analysis due to a lack of inter-isolate conservation. An additional 391 proteins were eliminated from assessment to avoid potential autoimmune responses due to the presence of host homology. We analyzed the remaining 1022 proteins for their ability to produce peptides that bind MHCI or MHCII. MHCI and MHCII predicted epitopes were filtered and compared between species yielding 777 MHCI epitopes and 453 MHCII epitopes. These epitopes were further examined for presentation by both MHCI and MHCII, and for proteins that contained multiple epitopes. There were 31 epitopes that overlapped positionally between MHCI and MHCII across host species. Of these, there were 9 epitopes represented within proteins containing ≥ 5 total epitopes, where an additional 24 proteins were also epitope dense. In all, 55 proteins were found to contain high scoring T-cell epitopes. Besides the well-studied protein Com1, most identified proteins were novel when compared to previously studied vaccine candidates.

Conclusion

These data represent the first proteome-wide evaluation of C. burnetii peptide epitopes. Furthermore, the inclusion of human, mouse, and bovine data capture a range of hosts for this zoonotic pathogen plus an important model organism. This work provides new vaccine targets for future vaccination efforts and enhances opportunities for selecting multiple T-cell epitope types to include within a vaccine.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12859-021-04181-w.

Correlating Genotyping Data of Coxiella burnetii with Genomic Groups

Coxiella burnetii is a zoonotic pathogen that resides in wild and domesticated animals across the globe and causes a febrile illness, Q fever, in humans. Several distinct genetic lineages or genomic groups have been shown to exist, with evidence for different virulence potential of these lineages. Multispacer Sequence Typing (MST) and Multiple-Locus Variable number tandem repeat Analysis (MLVA) are being used to genotype strains. However, it is unclear how these typing schemes correlate with each other or with the classification into different genomic groups. Here, we created extensive databases for published MLVA and MST genotypes of C. burnetii and analysed the associated metadata, revealing associations between animal host and human disease type. We established a new classification scheme that assigns both MST and MLVA genotypes to a genomic group and which revealed additional sub-lineages in two genomic groups. Finally, we report a novel, rapid genomotyping method for assigning an isolate into a genomic group based on the Cox51 spacer sequence. We conclude that by pooling and streamlining existing datasets, associations between genotype and clinical outcome or host source were identified, which in combination with our novel genomotyping method, should enable an estimation of the disease potential of new C. burnetii isolates.

The Coxiella burnetii T4SS Effector AnkF Is Important for Intracellular Replication

Coxiella burnetii is an obligate intracellular pathogen and the causative agent of the zoonotic disease Q fever. Following uptake by alveolar macrophages, the pathogen replicates in an acidic phagolysosomal vacuole, the C. burnetii-containing vacuole (CCV). Effector proteins translocated into the host cell by the type IV secretion system (T4SS) are important for the establishment of the CCV. Here we focus on the effector protein AnkF and its role in establishing the CCV. The C. burnetii AnkF knock out mutant invades host cells as efficiently as wild-type C. burnetii, but this mutant is hampered in its ability to replicate intracellularly, indicating that AnkF might be involved in the development of a replicative CCV. To unravel the underlying reason(s), we searched for AnkF interactors in host cells and identified vimentin through a yeast two-hybrid approach. While AnkF does not alter vimentin expression at the mRNA or protein levels, the presence of AnkF results in structural reorganization and vesicular co-localization with recombinant vimentin. Ectopically expressed AnkF partially accumulates around the established CCV and endogenous vimentin is recruited to the CCV in a time-dependent manner, suggesting that AnkF might attract vimentin to the CCV. However, knocking-down endogenous vimentin does not affect intracellular replication of C. burnetii. Other cytoskeletal components are recruited to the CCV and might compensate for the lack of vimentin. Taken together, AnkF is essential for the establishment of the replicative CCV, however, its mode of action is still elusive.

From cell culture to cynomolgus macaque: infection models show lineage-specific virulence potential of Coxiella burnetii

Coxiella burnetii is an obligate intracellular pathogen that causes the zoonotic disease Q fever in humans, which can occur in either an acute or a chronic form with serious complications. The bacterium has a wide host range, including unicellular organisms, invertebrates, birds and mammals, with livestock representing the most significant reservoir for human infections. Cell culture models have been used to decipher the intracellular lifestyle of C. burnetii, and several infection models, including invertebrates, rodents and non-human primates, are being used to investigate host-pathogen interactions and to identify bacterial virulence factors and vaccine candidates. However, none of the models replicate all aspects of human disease. Furthermore, it is becoming evident that C. burnetii isolates belonging to different lineages exhibit differences in their virulence in these models. Here, we compare the advantages and disadvantages of commonly used infection models and summarize currently available data for lineage-specific virulence.

Extensive genome analysis of Coxiella burnetii reveals limited evolution within genomic groups

BACKGROUND

Coxiella burnetii is a zoonotic pathogen that resides in wild and domesticated animals across the globe and causes a febrile illness, Q fever, in humans. An improved understanding of the genetic diversity of C. burnetii is essential for the development of diagnostics, vaccines and therapeutics, but genotyping data is lacking from many parts of the world. Sporadic outbreaks of Q fever have occurred in the United Kingdom, but the local genetic make-up of C. burnetii has not been studied in detail.

RESULTS

Here, we report whole genome data for nine C. burnetii sequences obtained in the UK. All four genomes of C. burnetii from cattle, as well as one sheep sample, belonged to Multi-spacer sequence type (MST) 20, whereas the goat samples were MST33 (three genomes) and MST32 (one genome), two genotypes that have not been described to be present in the UK to date. We established the phylogenetic relationship between the UK genomes and 67 publically available genomes based on single nucleotide polymorphisms (SNPs) in the core genome, which confirmed tight clustering of strains within genomic groups, but also indicated that sub-groups exist within those groups. Variation is mainly achieved through SNPs, many of which are non-synonymous, thereby confirming that evolution of C. burnetii is based on modification of existing genes. Finally, we discovered genomic-group specific genome content, which supports a model of clonal expansion of previously established genotypes, with large scale dissemination of some of these genotypes across continents being observed.

CONCLUSIONS

The genetic make-up of C. burnetii in the UK is similar to the one in neighboring European countries. As a species, C. burnetii has been considered a clonal pathogen with low genetic diversity at the nucleotide level. Here, we present evidence for significant variation at the protein level between isolates of different genomic groups, which mainly affects secreted and membrane-associated proteins. Our results thereby increase our understanding of the global genetic diversity of C. burnetii and provide new insights into the evolution of this emerging zoonotic pathogen.

The hypervirulent Coxiella burnetii Guiana strain compared in silico, in vitro and in vivo to the Nine Mile and the German strain

OBJECTIVE

Q fever epidemic outbreaks have been reported in French Guiana and in The Netherlands. To determine whether the C. burnetii strains involved in these epidemics had a peculiar virulence pattern, we compared the pathogenicity of the Guiana and the German strain (a clone of The Netherlands strain), in silico, in vitro, and in vivo versus the Nine Mile strain.

METHOD

The pan-genomes of the Guiana (Cb175), German (Z3055), and the referent Nine Mile (RSA 493) C. burnetii strains were compared. In vitro, the growth rate and the morphological presentation were compared. In vivo (SCID and Balb/c mice), weight loss, histological lesions, C. burnetii bacterial load in deep organs, and serological response were reported according to each C. burnetii strain studied.

RESULTS

The Guiana strain had 77 times more missing genes and 12 times more unique genes than the German strain. The Guiana strain presented as large cell variants (LCVs) and led to the most pronounced fatality rate in SCID mice (100% at 4 weeks). The German strain presented as small cell variants (SCVs), and had an intermediate fatality rate (75% at 4 weeks). Both the Guiana and the German strains led to a significant higher serological response at 2 and 4 weeks post infection (p <0.05).

CONCLUSION

The Guiana strain was the most virulent strain, followed by the German strain and the referent Nine Mile strain. Unique and missing genes could be implicated but further investigations are necessary to specify their role.

A systematic knowledge synthesis on the spatial dimensions of Q fever epidemics

From 2007 through 2010, the Netherlands experienced the largest Q fever epidemic ever reported. This study integrates the outcomes of a multidisciplinary research programme on spatial airborne transmission of Coxiella burnetii and reflects these outcomes in relation to other scientific Q fever studies worldwide. We have identified lessons learned and remaining knowledge gaps. This synthesis was structured according to the four steps of quantitative microbial risk assessment (QMRA): (a) Rapid source identification was improved by newly developed techniques using mathematical disease modelling; (b) source characterization efforts improved knowledge but did not provide accurate C. burnetii emission patterns; (c) ambient air sampling, dispersion and spatial modelling promoted exposure assessment; and (d) risk characterization was enabled by applying refined dose–response analyses. The results may support proper and timely risk assessment and risk management during future outbreaks, provided that accurate and structured data are available and exchanged readily between responsible actors.

Genetic diversity of Coxiella burnetii in domestic ruminants in central Italy

Background

As the epidemiology of human Q Fever generally reflects the spread of Coxiella burnetii in ruminant livestock, molecular characterization of strains is essential to prevent human outbreaks. In this study we report the genetic diversity of C. burnetii in central Italy accomplished by MST and MLVA-6 on biological samples from 20 goat, sheep and cow farms.

Results

Five MST and ten MLVA profiles emerged from the analysis establishing a part of C. burnetii strain world atlas. In particular, ST32 occurred on 12 farms (60%), prevalently in goat specimens, while ST12 (25%) was detected on 4 sheep and 1 goat samples. ST8 and a variant of this genotype were described on 2 different sheep farms, whereas ST55 was observed on a goat farm. Five complete MLVA profiles different from any other published genotypes were described in this study in addition to 15 MLVA incomplete panels. Despite this, polymorphic markers Ms23, Ms24 and Ms33 enabled the identification of samples sharing the same MST profile.

Conclusions

Integration of such data in international databases can be of further help in the attempt of building a global phylogeny and epidemiology of Q fever in animals, with a “One Health” perspective.

Comparison of genomes of Coxiella burnetii strains using formal order analysis

The Coxiella burnetii strain NL3262 was isolated during the Q fever outbreak in the Netherlands in 2007–2010. Formal-order analysis (FOA) was used to study the similarity of the genome (chromosome and plasmid) of this strain with the genomes from other strains. Chromosomes from ten C. burnetii strains and eight plasmids were studied with FOA tools such as ‘Map of genes’ and ‘Matrix of similarity.’ The ‘Map of genes’ tool showed that the chromosome of strain C. burnetii str. NL3262 distanced itself by the index of average remoteness (g) of 1.449640 (x-axis) from chromosomes of other strains (g 1.448295–1.448865). The ‘Matrix of similarity’ was used for an advanced analysis of the obtained results. The complete similarity of the components of chromosomes and plasmids was determined by pairwise comparison and the identification of nucleotides matching with them. A total of 84.90% of the chromosomal components of C. burnetii strain NL3262 coincided completely with the chromosomal components of strain Z3055. For chromosomes of other strains, this percentage varied from 12.06% to 47.14%. The plasmid of strain NL3262 had 50.0% of the components being completely coincident with the components of the plasmid of RSA 331; with RSA 493 it was 29.89%. Thus, C. burnetii str. NL3262 is the closest to str. Z3055 by the similarity of the chromosomal components, but on the index of average remoteness of the chromosome and the similarity of the plasmids' QpH1 components, it is the closest to strain RSA 331.

Coxiella burnetii isolates originating from infected cattle induce a more pronounced proinflammatory cytokine response compared to isolates from infected goats and sheep

Coxiella burnetii is the causative agent of Q fever. Although the prevalence of C. burnetii in cattle is much higher than in goats and sheep, infected cattle are rarely associated with human outbreaks. We investigated whether the immune response of humans differs after contact with C. burnetii isolates from different host origins or with different multilocus variable number of tandem repeat analysis (MLVA) genotypes. Cytokine responses were measured in human peripheral blood mononuclear cells (PBMCs) stimulated with 16 C. burnetii isolates with known MLVA genotype from goats, sheep, cattle, acute and chronic Q fever patients. Coxiella burnetii isolates originating from cattle induce significantly more IL-1β, TNF-α and IL-22 than the isolates from goats, sheep or chronic Q fever patients. Comparing the cytokine induction of the isolates based on their MVLA genotype did not reveal differences in response between the MLVA genotypes. The proinflammatory cytokine response induced in human PBMCs by C. burnetii isolates from cattle may explain the low incidence of human Q fever outbreaks caused by cattle. The cytokine profile of PBMCs stimulated with C. burnetii isolates from chronic Q fever patients resembles isolates from goats. Furthermore, cytokine responses seem to be depending on host origin than on MLVA genotype.

Culture-independent genome sequencing of Coxiella burnetii from a native heart valve of a Tunisian patient with severe infective endocarditis

We report draft genome of a Coxiella burnetii strain sequenced from the native valve of a patient presenting with severe endocarditis in Tunisia. The genome could be sequenced without a cellular or axenic culture step. The MST5 strain was demonstrated to be closely related to the published reference genome of C. burnetii CbuK_Q154.

Phylogenetic inference of Coxiella burnetii by 16S rRNA gene sequencing

Coxiella burnetii is a human pathogen that causes the serious zoonotic disease Q fever. It is ubiquitous in the environment and due to its wide host range, long-range dispersal potential and classification as a bioterrorism agent, this microorganism is considered an HHS Select Agent. In the event of an outbreak or intentional release, laboratory strain typing methods can contribute to epidemiological investigations, law enforcement investigation and the public health response by providing critical information about the relatedness between C. burnetii isolates collected from different sources. Laboratory cultivation of C. burnetii is both time-consuming and challenging. Availability of strain collections is often limited and while several strain typing methods have been described over the years, a true gold-standard method is still elusive. Building upon epidemiological knowledge from limited, historical strain collections and typing data is essential to more accurately infer C. burnetii phylogeny. Harmonization of auspicious high-resolution laboratory typing techniques is critical to support epidemiological and law enforcement investigation. The single nucleotide polymorphism (SNP) -based genotyping approach offers simplicity, rapidity and robustness. Herein, we demonstrate SNPs identified within 16S rRNA gene sequences can differentiate C. burnetii strains. Using this method, 55 isolates were assigned to six groups based on six polymorphisms. These 16S rRNA SNP-based genotyping results were largely congruent with those obtained by analyzing restriction-endonuclease (RE)-digested DNA separated by SDS-PAGE and by the high-resolution approach based on SNPs within multispacer sequence typing (MST) loci. The SNPs identified within the 16S rRNA gene can be used as targets for the development of additional SNP-based genotyping assays for C. burnetii.

Genome Plasticity and Polymorphisms in Critical Genes Correlate with Increased Virulence of Dutch Outbreak-Related Coxiella burnetii Strains

Coxiella burnetii is an obligate intracellular bacterium and the etiological agent of Q fever. During 2007-2010 the largest Q fever outbreak ever reported occurred in The Netherlands. It is anticipated that strains from this outbreak demonstrated an increased zoonotic potential as more than 40,000 individuals were assumed to be infected. The acquisition of novel genetic factors by these C. burnetii outbreak strains, such as virulence-related genes, has frequently been proposed and discussed, but is not proved yet. In the present study, the whole genome sequence of several Dutch strains (CbNL01 and CbNL12 genotypes), a few additionally selected strains from different geographical locations and publicly available genome sequences were used for a comparative bioinformatics approach. The study focuses on the identification of specific genetic differences in the outbreak related CbNL01 strains compared to other C. burnetii strains. In this approach we investigated the phylogenetic relationship and genomic aspects of virulence and host-specificity. Phylogenetic clustering of whole genome sequences showed a genotype-specific clustering that correlated with the clustering observed using Multiple Locus Variable-number Tandem Repeat Analysis (MLVA). Ortholog analysis on predicted genes and single nucleotide polymorphism (SNP) analysis of complete genome sequences demonstrated the presence of genotype-specific gene contents and SNP variations in C. burnetii strains. It also demonstrated that the currently used MLVA genotyping methods are highly discriminatory for the investigated outbreak strains. In the fully reconstructed genome sequence of the Dutch outbreak NL3262 strain of the CbNL01 genotype, a relatively large number of transposon-linked genes were identified as compared to the other published complete genome sequences of C. burnetii. Additionally, large numbers of SNPs in its membrane proteins and predicted virulence-associated genes were identified in all Dutch outbreak strains compared to the NM reference strain and other strains of the CbNL12 genotype. The presence of large numbers of transposable elements and mutated genes, thereof most likely resulted in high level of genome rearrangements and genotype-specific pathogenicity of outbreak strains. Thus, the epidemic potential of Dutch outbreak strains could be linked to increased genome plasticity and mutations in critical genes involved in virulence and the evasion of the host immune system.

Critical Aspects for Detection of Coxiella burnetii

Coxiella burnetii is a globally distributed zoonotic γ-proteobacterium with an obligatory intracellular lifestyle. It is the causative agent of Q fever in humans and of coxiellosis among ruminants, although the agent is also detected in ticks, birds, and various other mammalian species. Requirements for intracellular multiplication together with the necessity for biosafety level 3 facilities restrict the cultivation of C. burnetii to specialized laboratories. Development of a novel medium formulation enabling axenic growth of C. burnetii has facilitated fundamental genetic studies. This review provides critical insights into direct diagnostic methods currently available for C. burnetii. It encompasses molecular detection methods, isolation, and propagation of the bacteria and its genetic characterization. Differentiation of C. burnetii from Coxiella-like organisms is an essential diagnostic prerequisite, particularly when handling and analyzing ticks.

From Q Fever to Coxiella burnetii Infection: a Paradigm Change

Coxiella burnetii is the agent of Q fever, or "query fever," a zoonosis first described in Australia in 1937. Since this first description, knowledge about this pathogen and its associated infections has increased dramatically. We review here all the progress made over the last 20 years on this topic. C. burnetii is classically a strict intracellular, Gram-negative bacterium. However, a major step in the characterization of this pathogen was achieved by the establishment of its axenic culture. C. burnetii infects a wide range of animals, from arthropods to humans. The genetic determinants of virulence are now better known, thanks to the achievement of determining the genome sequences of several strains of this species and comparative genomic analyses. Q fever can be found worldwide, but the epidemiological features of this disease vary according to the geographic area considered, including situations where it is endemic or hyperendemic, and the occurrence of large epidemic outbreaks. In recent years, a major breakthrough in the understanding of the natural history of human infection with C. burnetii was the breaking of the old dichotomy between "acute" and "chronic" Q fever. The clinical presentation of C. burnetii infection depends on both the virulence of the infecting C. burnetii strain and specific risks factors in the infected patient. Moreover, no persistent infection can exist without a focus of infection. This paradigm change should allow better diagnosis and management of primary infection and long-term complications in patients with C. burnetii infection.

Coxiella burnetii Endocarditis in a Child Caused by a New Genotype

Coxiella burnetii endocarditis is a rare diagnosis in children. We present a case of Q fever endocarditis due to a new genotype, MST 54, and review recent literature on Q fever infections in children. Practitioners should consider Q fever in culture-negative endocarditis, particularly in children with congenital heart disease and history of travel or residence in endemic regions.

The contribution of genomics to the study of Q fever

Coxiella burnetii is the etiological agent of Q fever, a worldwide zoonosis that can result in large outbreaks. The birth of genomics and sequencing of C. burnetii strains has revolutionized many fields of study of this infection. Accurate genotyping methods and comparative genomic analysis have enabled description of the diversity of strains around the world and their link with pathogenicity. Genomics has also permitted the development of qPCR tools and axenic culture medium, facilitating the diagnosis of Q fever. Moreover, several pathophysiological mechanisms can now be predicted and therapeutic strategies can be determined thanks to in silico genome analysis. An extensive pan-genomic analysis will allow for a comprehensive view of the clonal diversity of C. burnetii and its link with virulence.

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Q fever is a zoonosis of worldwide distribution with the exception of New Zealand. It is caused by an intracellular bacterium, Coxiella burnetii. The disease often goes underdiagnosed because the main manifestation of its acute form is a general self-limiting flu-like syndrome. The Dutch epidemics renewed attention to this disease, which was less considered before. This review summarizes the description of C. burnetii (taxonomy, intracellular cycle, and genome) and Q fever disease (description, diagnosis, epidemiology, and pathogenesis). Finally, vaccination in humans and animals is also considered.

First Draft Genome Sequence of a Human Coxiella burnetii Isolate, Originating from the Largest Q Fever Outbreak Ever Reported, the Netherlands, 2007 to 2010

In 2009, Coxiella burnetii caused a large regional outbreak of Q fever in South Limburg, the Netherlands. Here, we announce the genome draft sequence of a human C. burnetii isolate, strain NL-Limburg, originating from this outbreak, including a brief summary of the genome’s general features.