Serotyping Coxiella burnetii isolates from acute and chronic Q fever patients by using monoclonal antibodies

Molecular and seroepidemiological investigation of Сoxiella burnetii and spotted fever group rickettsiae in the southern region of Kazakhstan

Ticks are involved in the circulation of a number of human pathogens, including spotted fever group (SFG) Rickettsia spp. and Coxiella burnetii. Little is known about the occurrence of these microorganisms in the southern region of Kazakhstan. In 2018-2022, a total of 726 ticks were collected from bitten humans, livestock, and vegetation in four oblasts of the southern region of Kazakhstan and subjected to DNA extraction. The overall infection rate of Coxiella spp. and Rickettsia spp. in the ticks was 3.3% (24/726) and 69.9% (300/429), respectively. Phylogenetic analysis of ompA and gltA genes revealed the presence of three pathogenic SFG rickettsiae: Candidatus R. tarasevichiae, R. aeschlimannii and R. raoultii in ticks collected from bitten humans. In addition, Candidatus R. barbariae was detected in six Rhipicephalus turanicus ticks for the first time in Kazakhstan. To determine the seroprevalence of C. burnetii infection, we performed a serological analysis of samples collected from 656 domestic ruminants (cattle, sheep, and goats) in the region. Overall, 23.5% (154/656) of the animals tested were positive for IgG against C. burnetii. Seroprevalence at the herd level was 54% (28/52). Goats (43%; 12/28; odds ratio (OD) = 28.9, p < 0.05) and sheep (31.9%; 137/430; OD = 18.1, p < 0.05) had higher seroprevalence than cattle (2.5%; 5/198). Among the risk factors considered in this study, age (p = 0.003) and the oblast in which the animals were sampled (p = 0.049) were statistically associated with seropostivity for Q fever in sheep, according to the results of multivariate logistic regression analysis. Seroprevalence ranged from 0% to 55.5% in animals in different districts of the southern region of Kazakhstan. Active C. burnetii bacteremia was detected in four of 154 (2.6%) seropositive animals. The data obtained provide strong evidence of the presence of pathogenic rickettsiae and C. burnetii in the southern region of Kazakhstan and emphasize the need to improve epidemiological surveillance in the region.

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.

Q Fever: an old but still a poorly understood disease

Q fever is a bacterial infection affecting mainly the lungs, liver, and heart. It is found around the world and is caused by the bacteria Coxiella burnetii. The bacteria affects sheep, goats, cattle, dogs, cats, birds, rodents, and ticks. Infected animals shed this bacteria in birth products, feces, milk, and urine. Humans usually get Q fever by breathing in contaminated droplets released by infected animals and drinking raw milk. People at highest risk for this infection are farmers, laboratory workers, sheep and dairy workers, and veterinarians. Chronic Q fever develops in people who have been infected for more than 6 months. It usually takes about 20 days after exposure to the bacteria for symptoms to occur. Most cases are mild, yet some severe cases have been reported. Symptoms of acute Q fever may include: chest pain with breathing, cough, fever, headache, jaundice, muscle pains, and shortness of breath. Symptoms of chronic Q fever may include chills, fatigue, night sweats, prolonged fever, and shortness of breath. Q fever is diagnosed with a blood antibody test. The main treatment for the disease is with antibiotics. For acute Q fever, doxycycline is recommended. For chronic Q fever, a combination of doxycycline and hydroxychloroquine is often used long term. Complications are cirrhosis, hepatitis, encephalitis, endocarditis, pericarditis, myocarditis, interstitial pulmonary fibrosis, meningitis, and pneumonia. People at risk should always: carefully dispose of animal products that may be infected, disinfect any contaminated areas, and thoroughly wash their hands. Pasteurizing milk can also help prevent Q fever.

Q Fever: current state of knowledge and perspectives of research of a neglected zoonosis

Q fever is an ubiquitous zoonosis caused by an resistant intracellular bacterium, Coxiella burnetii. In certain areas, Q fever can be a severe public health problem, and awareness of the disease must be promoted worldwide. Nevertheless, knowledge of Coxiella burnetii remains limited to this day. Its resistant (intracellular and environmental) and infectious properties have been poorly investigated. Further understanding of the interactions between the infected host and the bacteria is necessary. Domestic ruminants are considered as the main reservoir of bacteria. Infected animals shed highly infectious organisms in milk, feces, urine, vaginal mucus, and, very importantly, birth products. Inhalation is the main route of infection. Frequently asymptomatic in humans and animals, Q fever can cause acute or chronic infections. Financial consequences of infection can be dramatic at herd level. Vaccination with inactive whole-cell bacteria has been performed and proved effective in humans and animals. However, inactive whole-cell vaccines present several defects. Recombinant vaccines have been developed in experimental conditions and have great potential for the future. Q fever is a challenging disease for scientists as significant further investigations are necessary. Great research opportunities are available to reach a better understanding and thus a better prevention and control of the infection.

Genome-wide profiling of humoral immune response to Coxiella burnetii infection by protein microarray

Comprehensive evaluation of the humoral immune response to Coxiella burnetii may identify highly needed diagnostic antigens and potential subunit vaccine candidates. Here we report the construction of a protein microarray containing 1901 C. burnetii ORFs (84% of the entire proteome). This array was probed with Q-fever patient sera and naïve controls in order to discover C. burnetii-specific seroreactive antigens. Among the 21 seroreactive antigens identified, 13 were significantly more reactive in Q-fever cases than naïve controls. The remaining eight antigens were cross-reactive in both C. burnetii infected and naïve patient sera. An additional 64 antigens displayed variable seroreactivity in Q-fever patients, and underscore the diversity of the humoral immune response to C. burnetii. Nine of the differentially reactive antigens were validated on an alternative immunostrip platform, demonstrating proof-of-concept development of a consistent, safe, and inexpensive diagnostic assay alternative. Furthermore, we report here the identification of several new diagnostic antigens and potential subunit vaccine candidates for the highly infectious category B alphaproteobacteria, C. burnetii.

Vaccines against Coxiella infection

Coxiella burnetii is an obligate intracellular bacterium that causes a worldwide zoonotic disease, Q fever. Since C. burnetii infection is an occupational hazard and could develop into severe chronic disease in humans, vaccination should be considered to protect individuals at-risk of contact with naturally infected animals or exposure to the agents. Although several vaccines produced from Phase I whole-cell C. burnetii are effective in protecting against the infection in humans, vaccination of previously sensitized people can induce severe local and occasional systemic reactions. Safe use of these vaccines requires screening of potential vaccinees by skin tests, serological tests, or in vitro lymphocyte proliferation assay. Since these procedures are time-consuming and costly, they limit the use of whole-cell vaccines in a mass vaccination program. Efforts have been underway to develop a safer, more effective new-generation vaccine that will not cause adverse reactions when given to someone with pre-existing immunity. This article describes new information relating to the characterization of acquired immunity to C. burnetii infection that will provide a fundamental understanding of the development of protective immunity against Q fever. Recent works focused on development of recombinant vaccines against this pathogen offers promise in the pursuit of a new Q fever vaccine.

Identification and Characterization of Coxiella burnetii Strains and Isolates Using Monoclonal Antibodies

We evaluated 6 monoclonal antibodies (MAbs) for their usefulness in identifying and characterizing recognized laboratory strains as well as field isolates of Coxiella burnetii. Five had been generated in response to strain Nine Mile (3 IgM class, 1 IgG class, 1 light chain producers only) and were polypeptide-specific, and 1 was anti-Priscilla (IgG class) and was lipopolysaccharide (LPS)-specific. Initially, the MAbs were used in conjunction with a dot blot assay with which we could differentiate C. burnetii from rickettsiae or chlamydiae. Confirmation of the specificity of these MAbs was provided by demonstrating that only C. burnetii antigens were recognized by certain combinations of antibodies used for immunoblotting proteins of various C. burnetii strains. Subsequently, we characterized antigens of 11 C. burnetii field isolates and 3 reference strains by Western blotting with individual MAbs. MAb 921 and 922 (IgG class), MAb 241, 242, 384, 386, 614 (IgM class), and 7A5, 7A1 (light chain) consistently recognized a protein. Staining intensity differed, depending on the strain tested, and there was variability in the size of the antigen immunoreactive with MAb 14H (IgG class, LPS-specific). The most reactive region was at about 249 kD. Variability of reactivities with field isolates was seen in both the distribution of individual bands and their intensities. We conclude that an extensive immunoblotting technique may be useful for C. burnetii strain differentiation and routine identification of C. burnetii can be accomplished using this MAb-based dot blot assay.

Serotyping isolates of Anaplasma phagocytophilum by using monoclonal antibodies

Ten mouse monoclonal antibodies (MAbs) that react with Anaplasma phagocytophilum (the human granulocytic ehrlichiosis agent) Webster isolates were developed. Seven different isolates of A. phagocytophilum were subtyped with these MAbs. Western blot analysis revealed that these MAbs reacted mainly with 41- to 46-kDa Msp2 proteins. Six MAbs reacted with all isolates. Four other MAbs reacted with human isolates from Wisconsin, but not with human isolates from New York or with animal isolates. Three different serotypes were identified. These features may lead to the development of other specific MAbs in order to provide tools for antigenic characterization of human isolates of A. phagocytophilum.

Myocarditis, a rare but severe manifestation of Q fever: report of 8 cases and review of the literature

Myocarditis has only rarely been described as a manifestation of acute Q fever. Among our series of 1276 patients in whom acute Q fever was diagnosed during 1985--1999, myocarditis was diagnosed in 8. Two patients (25.0%) developed cardiac symptoms during the course of interstitial pneumonia, 2 (25.0%) initially presented with unexplained fever, and 1 (12.5%) presented with febrile cutaneous rash. In 3 patients, cardiac symptoms were inaugural: 1 patient experienced heart failure, and 2 experienced precordial pain. Dilated cardiomyopathy was documented in 7 patients, and 2 (1 of whom had undergone heart transplantation) died despite therapy. In addition, 1 patient was scheduled for heart transplantation because of cardiac insufficiency. When the patients in this study were compared with 32 control patients with acute Q fever, no specific epidemiological or clinical features were associated with this disease except worse prognosis (P=.006). Moreover, among the 12 patients from our series who died as a result of acute Q fever, 2 patients, who were significantly younger than the other 9 patients (P=.03), had myocarditis. Our study highlights the severity of Coxiella burnetii myocarditis.

Q fever epidemiology and pathogenesis

The lungs are a port of entry and primary infectious focus of Coxiella burnetii, the obligate intracellular contagium of the worldwide zoonosis Q fever. The infectious process and immune response are characterised by studies in cell culture and animal systems. Following endocytosis, replication exclusively occurs in the phagolysosome. Several potential virulence factors are described.

Intraspecies diversity of Coxiella burnetii as revealed by com1 and mucZ sequence comparison

Coxiella burnetii is classified within the gamma subgroup of the Proteobacteria. All strains tested to date have an identical 16S rRNA sequence but 20 different genotypes have been determined by pulsed field gel electrophoresis (PFGE). In this study, intraspecies genetic diversity was investigated by sequence comparison of 715 bp of the Com1 encoding gene (com1) and 774 bp of the MucZ encoding gene (mucZ) in 37 strains isolated from animals and humans with acute or chronic Q fever in Europe, North America and Africa. Five and four groups were established from sequence analysis of com1 and mucZ, respectively. Neither relation of the defined groups to geographical distribution of the isolates was noted nor relation to disease form (acute/chronic). The same isolates were grouped together regardless of the gene being investigated. Comparison of the five proposed groups to previous groups, yielded after digestion by NotI PFGE, allowed for an intermediate classification of C. burnetii isolates between those obtained by using 16S rDNA (one group) and PFGE (20 groups).

Q fever

Q fever is a zoonosis with a worldwide distribution with the exception of New Zealand. The disease is caused by Coxiella burnetii, a strictly intracellular, gram-negative bacterium. Many species of mammals, birds, and ticks are reservoirs of C. burnetii in nature. C. burnetii infection is most often latent in animals, with persistent shedding of bacteria into the environment. However, in females intermittent high-level shedding occurs at the time of parturition, with millions of bacteria being released per gram of placenta. Humans are usually infected by contaminated aerosols from domestic animals, particularly after contact with parturient females and their birth products. Although often asymptomatic, Q fever may manifest in humans as an acute disease (mainly as a self-limited febrile illness, pneumonia, or hepatitis) or as a chronic disease (mainly endocarditis), especially in patients with previous valvulopathy and to a lesser extent in immunocompromised hosts and in pregnant women. Specific diagnosis of Q fever remains based upon serology. Immunoglobulin M (IgM) and IgG antiphase II antibodies are detected 2 to 3 weeks after infection with C. burnetii, whereas the presence of IgG antiphase I C. burnetii antibodies at titers of >/=1:800 by microimmunofluorescence is indicative of chronic Q fever. The tetracyclines are still considered the mainstay of antibiotic therapy of acute Q fever, whereas antibiotic combinations administered over prolonged periods are necessary to prevent relapses in Q fever endocarditis patients. Although the protective role of Q fever vaccination with whole-cell extracts has been established, the population which should be primarily vaccinated remains to be clearly identified. Vaccination should probably be considered in the population at high risk for Q fever endocarditis.

Physical and genetic map of the obligate intracellular bacterium Coxiella burnetii

Pulsed-field gel electrophoresis and PCR techniques have been used to construct a NotI macrorestriction map of the obligate intracellular bacterium Coxiella burnetii Nine Mile. The size of the chromosome has been determined to be 2,103 kb comprising 29 NotI restriction fragments. The average resolution is 72.5 kb, or about 3. 5% of the genome. Experimental data support the presence of a linear chromosome. Published genes were localized on the physical map by Southern hybridization. One gene, recognized as transposable element, was found to be present in at least nine sites evenly distributed over the whole chromosome. There is only one copy of a 16S rRNA gene. The putative oriC has been located on a 27.5-kb NotI fragment. Gene organization upstream the oriC is almost identical to that of Pseudomonas putida and Bacillus subtilis, whereas gene organization downstream the oriC seems to be unique among bacteria. The physical map will be helpful in investigations of the great heterogeneity in restriction fragment length polymorphism patterns of different isolates and the great variation in genome size. The genetic map will help to determine whether gene order in different isolates is conserved.

Plasmid-homologous sequences in the chromosome of plasmidless Coxiella burnetii Scurry Q217

Chromosomal DNA from Coxiella burnetii Scurry Q217 was screened for the presence of plasmid-homologous sequences. Total DNA from Scurry Q217 was digested with NotI, and the resulting DNA fragments were separated by contour-clamped homogeneous electric field pulsed-field gel electrophoresis (CHEF-PFGE). Following hybridization with biotin-labeled QpH1 plasmid as a probe, two DNA fragments of 40 and 170 kb were identified as targets. These fragments were cloned, and subclones containing QpH1-homologous sequences were completely sequenced. The physical mapping of DNA fragments was achieved by PCR with primers derived from adjacent fragments, and a total of 18,360 bp was sequenced. Within the QpH1-homologous region spanning 16,624 bp, homology was as high as 99%. Deletions were identified within EcoRI fragments A(H)-C(H)-K(H)-B(H) (13,490 bp) and J(H)-G(H)-E(H)-L+-D(H) (6,509 bp) and in fragment A(H) alone (619 bp). An insertion of 744 bp was identified within the JDc region of Scurry Q217. A search for putative coding regions identified a total of 17 open reading frames (ORFs). Compared to plasmid QpH1, 6 ORFs were identical, 5 ORFs were different in size, 6 ORFs were newly generated, and 25 ORFs were lost. It was found that plasmid-homologous sequences in Scurry Q217 were of chromosomal origin.

Sequence of quinolone resistance-determining region of gyrA gene for clinical isolates and for an in vitro-selected quinolone-resistant strain of Coxiella burnetii

We report the sequence of the quinolone resistance-determining region of the gyrA genes of either susceptible or low-level-resistant clinical isolates of Coxiella burnetii. The sequences of low-level (MICs, 4 micrograms/ml) and high-level (MICs, 8 and 16 micrograms/ml) resistant strains stepwise selected in vitro were also determined. The gene sequences of all of the clinical isolates and that of the in vitro-selected low-level-resistant strain were identical. Sequence analysis of the in vitro-selected high-level-resistant strain revealed a nucleotide mutation leading to an amino acid substitution of Gly in place of Glu at position 87 of the GyrA amino acid sequence. These results indicate that high-level resistance to ciprofloxacin is associated with a nucleotide mutation in gyrA, whereas low-level resistance to quinolones is not.

Coxiella burnetii blood cultures from acute and chronic Q-fever patients

Q fever, a worldwide zoonosis caused by Coxiella burnetii, may present as either an acute or a chronic disease. We correlated the results of 844 C. burnetii blood cultures with serological, clinical, and therapeutic data. C. burnetii was isolated from 17% of untreated patients with acute Q fever and from 53% of untreated patients with chronic Q fever. C. burnetii was not isolated from patients who were receiving antibiotics active against C. burnetii. For seven culture-positive patients with acute Q fever, serology was negative when C. burnetii was isolated. One patient with acute Q fever had a positive blood culture 25 days after the discontinuation of specific antibiotic therapy, and another had a positive blood culture after the resolution of symptoms. In one case of chronic Q fever, a positive blood culture resulted from noncompliance with treatment. The culture method described in this report is suitable for all laboratories with cell culture facilities. Our findings suggest that blood samples must be collected prior to the initiation of an antibiotic regimen if C. burnetii is to be successfully isolated.

Monoclonal antibodies to Coxiella burnetii that cross-react with strain Nine Mile

Results are presented to show the binding properties of five monoclonal antibodies directed to Coxiella burnetii Priscilla with cross-reactions to the Nine Mile strain. The monoclonal antibodies preferentially recognize phase I epitopes by ELISA and recognize phase II epitopes by immunoblotting but do not allow differentiation between so-called chronic and acute strains of C. burnetii. The only difference in reactivity was in the staining pattern revealed after reactions with lipopolysaccharide I antigens.

Immunohistologic demonstration of Coxiella burnetii in the valves of patients with Q fever endocarditis

PURPOSE

Cardiac valves that were resected from patients with Q fever endocarditis were examined by immunohistologic methods to correlate the presence of Coxiella burnetii in the valves with the histopathologic, serologic, microbiologic, and clinical findings.

PATIENTS

Seventeen patients with serologic and microbiologic or clinical evidence of Q fever endocarditis who presented with cardiac failure secondary to valvular dysfunction and required valve replacement surgery were selected from the clinical records of the Unité des Rickettsies, Marseille, France.

METHODS

Clinical data were collected by questionnaire. Serologic characterization was performed by indirect immunofluorescent antibody testing; shell vial cultivation of C burnetii was performed from resected valves and blood when available; and pathologic and immunohistologic testing for localization of C burnetti in resected valves were performed by standard methods using both polyclonal and monoclonal C burnetti antibodies.

RESULTS

Demographic and clinical findings were typical of patients with Q fever endocarditis. Pure chronic inflammation or mixtures of acute and chronic inflammation were the most frequent inflammatory patterns present and were associated with fibrin deposition, necrosis, and fibrosis. Well-formed granulomas were not present, but the granulomatous inflammation observed in 6 of these 17 patients was associated with foreign body reactions or with valvular calcifications secondary to preexisting valvular damage and could not be directly attributed to infection. C burnetii were present nearly exclusively in macrophages in sites of inflammation and valvular injury and only in the vegetations. Immunohistologic results confirmed the valve culture results in 10 of 14 cases.

CONCLUSION

The pathologic findings in the valves of patients with Q fever endocarditis are nonspecific. The presence of empty or foamy macrophages is suggestive of infection by C burnetii; however, definitive identification rests upon the demonstration of the organism in the tissue by immunohistology. Q fever endocarditis probably results from infection of previously damaged heart valves. The finding of the absence of granulomas in these cases contrasts with the pathologic findings in patients with acute, self-limited Q fever and suggests an aberrant host immune response that permits persistence of the bacterium and chronic, prolonged valvular infection and injury. The pathologic findings and distribution of C burnetii in the damaged valve tissues explain the clinical findings of valve failure and occasional embolic episodes, as well as the frequent ability to isolate C burnetii from the peripheral blood of infected patients. Immunohistology may be a valuable diagnostic tool in places where serology and culture are not available.