Q fever endocarditis in the south of France

Treatment of persistent focalized Q fever: time has come for an international randomized controlled trial

Q fever is a worldwide zoonosis due to Coxiella burnetii, responsible for endocarditis and endovascular infections. Since the 1990s, the combination hydroxychloroquine + doxycycline has constituted the curative and prophylactic treatment in persistent focalized Q fever. This combination appears to have significantly reduced the treatment's duration (from 60 to 26 months), yet substantial evidence of effectiveness remains lacking. Data are mostly based on in vitro and observational studies. We conducted a literature review to assess the effectiveness of this therapy, along with potential alternatives. The proposed in vitro mechanism of action describes the inhibition of Coxiella replication by doxycycline through the restoration of its bactericidal activity (inhibited in acidic environment) by alkalinization of phagolysosome-like vacuoles with hydroxychloroquine. So far, the rarity and heterogeneous presentation of cases have made it challenging to design prospective studies with statistical power. The main studies supporting this treatment are retrospective cohorts, dating back to the 1990s-2000s. Retrospective studies from the large Dutch outbreak of Q fever (>4000 cases between 2007 and 2010) did not corroborate a clear benefit of this combination, notably in comparison with other regimens. Thus, there is still no consensus among the medical community on this issue. However insufficient the evidence, today the doxycycline + hydroxychloroquine combination remains the regimen with the largest clinical experience in the treatment of 'chronic' Q fever. Reinforcing the guidelines' level of evidence is critical. We herein propose the creation of an extensive international registry, followed by a prospective cohort or ideally a randomized controlled trial.

Tracking the Source of Human Q Fever from a Southern French Village: Sentinel Animals and Environmental Reservoir

Coxiella burnetii, also known as the causal agent of Q fever, is a zoonotic pathogen infecting humans and several animal species. Here, we investigated the epidemiological context of C. burnetii from an area in the Hérault department in southern France, using the One Health paradigm. In total, 13 human cases of Q fever were diagnosed over the last three years in an area comprising four villages. Serological and molecular investigations conducted on the representative animal population, as well as wind data, indicated that some of the recent cases are likely to have originated from a sheepfold, which revealed bacterial contamination and a seroprevalence of 47.6%. However, the clear-cut origin of human cases cannot be ruled out in the absence of molecular data from the patients. Multi-spacer typing based on dual barcoding nanopore sequencing highlighted the occurrence of a new genotype of C. burnetii. In addition, the environmental contamination appeared to be widespread across a perimeter of 6 km due to local wind activity, according to the seroprevalence detected in dogs (12.6%) and horses (8.49%) in the surrounding populations. These findings were helpful in describing the extent of the exposed area and thus supporting the use of dogs and horses as valuable sentinel indicators for monitoring Q fever. The present data clearly highlighted that the epidemiological surveillance of Q fever should be reinforced and improved.

A Narrative Review of Q Fever in Europe

Coxiella burnetii, the causative agent of Q fever, causes abortions in animals. Its effects on humans and the management of Q fever in certain conditions like pregnancy are undetermined. The World Health Organization has estimated that zoonotic diseases cause around one billion cases of infections and millions of deaths globally each year. It is worth noting that many emerging infectious diseases currently being reported worldwide are zoonoses. We reviewed studies reporting on Q fever prevalence and incidence in Europe. Articles from 1937 to 2023 with the following terms "Coxiella burnetii and Europe and Q fever, and seroprevalence studies" were identified in the PubMed database and reports by organizations such as the European Centre for Disease Prevention and Control (ECDC). We included randomized and observational studies, seroprevalence studies, case series, and case reports. According to the ECDC in 2019, 23 countries reported 1069 cases, the majority of which were classified as confirmed cases. The number of reports per 100,000 inhabitants in the EU/EEA was 0.2 for 2019, the same as the previous four years. The highest report rate (0.7 cases per 100,000 population) was observed in Spain, followed by Romania (0.6), Bulgaria (0.5), and Hungary. Considering the typically asymptomatic nature of Q fever infection, it is imperative to strengthen the existing systems to promote the rapid identification and reporting of Q fever outbreaks in animals, particularly in cases of abortion. It is also essential to consider the facilitation of early information exchange between veterinarians and public health counterparts to ensure the timely detection and prevention of potential zoonotic events, including Q fever.

T-Bet Controls Susceptibility of Mice to Coxiella burnetii Infection

T-bet is a transcription factor known to initiate and coordinate the gene expression program during Th1 differentiation, which is crucial for clearance of intracellular pathogens. Q fever is a worldwide zoonosis caused by Coxiella burnetii. This bacterium is transmitted to humans by aerosol. Indeed, the inhibition of the Coxiella-specific adaptive Th1 immune response leads to persistent infection and organ injury. How deficiency of T-bet affects host infection by C. burnetii has not been investigated. Here, using mice with a deletion of the T-bet gene and an airborne mode of infection to reproduce the natural conditions of C. burnetii infection, we show that infected T-bet^–/– mice were more affected than wild-type mice. The lack of T-bet leads to defective bacterial control, intense replication, persistent infection, and organ injury manifesting as an increased number of granulomas. The absence of T-bet was also associated with an impaired immune response. Indeed, the production of the immunomodulatory cytokines interleukin (IL)-6 and IL-10 was increased, whereas the expression of microbicidal genes by splenocytes was impaired. Moreover, the absence of T-bet exhibited impaired production of interferon-γ, the principal cytokine released by Th1 effector cells. Thus, our study highlights the key role of T-bet in the control of C. burnetii infection in mice and leads to a reappraisal of granulomas in the pathogenesis of Q fever disease.

Screening for Q fever. A tertiary care hospital-based experience in central Saudi Arabia

OBJECTIVES

To evaluate the presence of Coxiella burnetii  (C. brunetii) infection among patients presenting with fever of unknown origin (FUO).

METHODS

A cross-sectional study of 100 patients (54 men and 46 women; mean age: 34.3 ± 19.2 years) with FUO was conducted at King Khalid University Hospital, Riyadh, Saudi Arabia between March 2015 and June 2016. Phase 1 and phase 2 C. burnetii-specific antibodies in serum samples were detected by enzyme-linked immunosorbent assay.

RESULTS

Coxiella burnetii phase 1 and phase 2 antibodies were detected in 16% of the patients. Phase 2 IgM was present in 2% of the patients, whereas phase 2 IgG antibodies were detected in 11%  of the patients. Coxiella burnetii-specific phase 1 IgG was found in 2% of the patients, and 8% of the patients harbored phase 1 IgA antibodies in their serum.

CONCLUSION

The presence of C. burnetii-specific antibodies in many patients suffering from FUO highlights the importance of Q fever screening among patients presenting with febrile illness.

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.

Antibody kinetics in serological indication of chronic Q fever: the Greek experience

BACKGROUND

Q fever caused by the pathogen Coxiella burnetii may have both acute and chronic manifestations. Although paired sera are not required for the diagnosis of chronic Q fever, monitoring of antibody titers can be used to examine the course of treatment. Monitoring both phase II and phase I antibodies may be of limited diagnostic value, but it is a useful means of determining the response to treatment and possible disease relapses.

METHODS

In the current survey we determined IgG and IgM of both phase I and phase II for 35 patients suffering from chronic Q fever in an attempt to draw conclusions on the kinetics of the antibodies throughout the course of the disease.

RESULTS

Overall, 33 cases were included in the study. Of the 33 patients, 32 had a good outcome.

CONCLUSIONS

Our findings support the general belief that a long period of serological monitoring is required for patients with chronic Q fever.

Microevolution of the chromosomal region of acute disease antigen A (adaA) in the query (Q) fever agent Coxiella burnetii

The acute disease antigen A (adaA) gene is believed to be associated with Coxiella burnetii strains causing acute Q fever. The detailed analysis of the adaA genomic region of 23 human- and 86 animal-derived C. burnetii isolates presented in this study reveals a much more polymorphic appearance and distribution of the adaA gene, resulting in a classification of C. burnetii strains of better differentiation than previously anticipated. Three different genomic variants of the adaA gene were identified which could be detected in isolates from acute and chronic patients, rendering the association of adaA positive strains with acute Q fever disease disputable. In addition, all adaA positive strains in humans and animals showed the occurrence of the QpH1 plasmid. All adaA positive isolates of acute human patients except one showed a distinct SNP variation at position 431, also predominant in sheep strains, which correlates well with the observation that sheep are a major source of human infection. Furthermore, the phylogenetic analysis of the adaA gene revealed three deletion events and supported the hypothesis that strain Dugway 5J108-111 might be the ancestor of all known C. burnetii strains. Based on our findings, we could confirm the QpDV group and we were able to define a new genotypic cluster. The adaA gene polymorphisms shown here improve molecular typing of Q fever, and give new insights into microevolutionary adaption processes in C. burnetii.

Chronic Q fever: expert opinion versus literature analysis and consensus

Q fever has long been considered a rare disease. The extensive outbreak in the Netherlands generated a body of literature based solely on the consensus in the Netherlands. As a long-standing expert on Q fever, I offer my experience and recommendations to the E-CDC and the Dutch Q fever Consensus Group. My (biased) opinion is that experts deeply involved in the field continue to be useful in the management of outbreaks and can avoid decisions that produce an unfavorable progression in patients. Here, I propose that the definition of "chronic Q fever" be avoided and suggest a new score-based diagnosis for Q fever endocarditis and vascular infection.

Long-term outcome of Q fever endocarditis: a 26-year personal survey

BACKGROUND

Q fever endocarditis caused by Coxiella burnetii is a potentially fatal disease characterised by a chronic evolution. To assess the long-term outcome and identify prognostic factors for mortality, surgical treatment, and serological changes in Q fever endocarditis, we did a retrospective study in the French National Referral Centre.

METHODS

Patients included were diagnosed with Q fever endocarditis at our centre from May, 1983, to June, 2006, and followed up for a minimum of 3 years for each patient, history and clinical characteristics were recorded with a standardised questionnaire. Prognostic factors associated with death, surgery, serological cure, and serological relapse were assessed by Cox regression analysis. Excised heart valve analysis was assessed according to duration of treatment.

FINDINGS

104 patients were identified for inclusion in the study, although one was lost to follow-up; median follow-up was 100 months (range 37-310 months). 18 months of treatment was sufficient to sterilise the valves of all the patients except three, and 2 years of treatment sterilised all valves except one. In a multivariate Cox regression analysis, the major determinants associated with mortality were age (hazard ratio 1.11, 95% CI 1.05-1.18, p=0.003), stroke at diagnosis (7.09, 2.00-25.10, p=0.001), endocarditis on a prosthetic valve (6.04, 1.47-24.80, p=0.044), an absence of a four-times decrease of phase I IgG and IgA at 1 year (5.69, 1.00-32.22, p=0.049), or the presence of phase II IgM at 1 year (12.08, 3.11-46.85, p=0.005). Surgery was associated with heart failure (2.68, 1.21-5.94, p=0.015) or a cardiac abscess (4.71, 1.64-13.50, p=0.004). The determinants of poor serological outcome were male sex (0.47, 0.26-0.86, p=0.014), a high level of phase I IgG (0.65, 0.45-0.95, p=0.027), and a delay in the start of treatment with hydroxychloroquine (0.20, 0.04-0.91, p=0.037). Factors associated with relapse were endocarditis on a prosthetic valve (21.3, 2.05-221.86, p=0.01) or treatment duration less than 18 months (9.69, 1.08-86.72, p=0.042).

INTERPRETATION

The optimum duration of treatment with doxycycline and hydroxychloroquine in Q fever endocarditis is 18 months for native valves and 24 months for prosthetic valves. This duration should be extended only in the absence of favourable serological outcomes. Patients should be serologically monitored for at least 5 years because of the risk of relapse.

FUNDING

French National Referral Centre for Q Fever.

Clinicopathologic aspects of animal and zoonotic diseases of bioterrorism

We live in an era of emerging infectious diseases and the threat of bioterrorism. Most of the infectious agents of modern concern, from plague to avian influenza H5N1, are zoonotic diseases: infectious agents that reside in quiet animal reservoir cycles that are transmitted occasionally to humans. The public health, health care, and veterinary communities have an enormous challenge in the early recognition, reporting, treatment, and prevention of zoonotic diseases. An intimate understanding of the natural ecology, geographic distribution, clinical signs, lesions, and diagnosis of these diseases is essential for the early recognition and control of these diseases.

Chronic Q fever in the United States

Infections due to Coxiella burnetii, the causative agent of Q fever, are uncommon in the United States. Cases of chronic Q fever are extremely rare and most often manifest as culture-negative endocarditis in patients with underlying valvular heart disease. We describe a 31-year-old farmer from West Virginia with a history of congenital heart disease and recurrent fevers for 14 months who was diagnosed with Q fever endocarditis based on an extremely high antibody titer against Coxiella burnetii phase I antigen. Despite treatment with doxycycline, he continued to have markedly elevated Coxiella burnetii phase I antibody titers for 10 years after the initial diagnosis. To our knowledge, this case represents the longest follow-up period for a patient with chronic Q fever in the United States. We review all cases of chronic Q fever reported in the United States and discuss important issues pertaining to epidemiology, diagnosis, and management of this disease.

Ongoing queries: Interpretation of serology in asymptomatic or atypical chronic Q fever

Chronic Q fever, predominantly associated with endocarditis, can develop insidiously. Although the diagnosis may be straightforward with a typical clinical presentation, incidental discovery of positive Coxiella burnetii serology poses a difficult clinical challenge. We describe the cases of two such patients and review the literature on the serological diagnosis of chronic Q fever.

Blood culture-negative endocarditis in a reference center: etiologic diagnosis of 348 cases

To identify the current etiologies of blood culture-negative infective endocarditis and to describe the epidemiologic, clinical, laboratory, and echocardiographic characteristics associated with each etiology, as well as with unexplained cases, we tested samples from 348 patients suspected of having blood culture-negative infective endocarditis in our diagnostic center, the French National Reference Center for Rickettsial Diseases, between 1983 and 2001. Serology tests for Coxiella burnettii, Bartonella species, Chlamydia species, Legionella species, and Aspergillus species; blood culture on shell vial; and, when available, analysis of valve specimens through culture, microscopic examination, and direct PCR amplification were performed. Physicians were asked to complete a questionnaire, which was computerized. Only cases of definite infective endocarditis, as defined by the modified Duke criteria, were included. A total of 348 cases were recorded-to our knowledge, the largest series reported to date. Of those, 167 cases (48%) were associated with C. burnetii, 99 (28%) with Bartonella species, and 5 (1%) with rare, fastidious bacterial agents of endocarditis (Tropheryma whipplei, Abiotrophia elegans, Mycoplasma hominis, Legionella pneumophila). Among 73 cases without etiology, 58 received antibiotic drugs before the blood cultures. Six cases were right-sided endocarditis and 4 occurred in patients who had a permanent pacemaker. Finally, no explanatory factor was found for 5 remaining cases (1%), despite all investigations.Q fever endocarditis affected males in 75% of cases, between 40 and 70 years of age. Ninety-one percent of patients had a previous valvulopathy, 32% were immunocompromised, and 70% had been exposed to animals. Our study confirms the improved clinical presentation and prognosis of the disease observed during the last decades. Such an evolution could be related to earlier diagnosis due to better physician awareness and more sensitive diagnostic techniques. As for Bartonella species, B. quintana was recorded more frequently than B. henselae (53 vs 17 cases). For 18 patients with Bartonella endocarditis, the responsible species was not identified. Species determination was achieved through culture and/or PCR in 49 cases and through Western immunoblotting in 22. Comparison of B. quintana and B. henselae endocarditis revealed distinct epidemiologic patterns. The 2 cases due to T. whipplei reflect the emerging role of this agent as a cause of infective endocarditis. Because identification of the bacterium was possible only through analysis of excised valves by histologic examination, PCR, and culture on shell vial, the prevalence of the disease might be underestimated. Among patients who received antibiotic drugs before blood cultures, 4 cases (7%) were found to be associated with Streptococcus species (2 S. bovis and 2 S. mutans) through 16S rDNA gene amplification directly from the valve, which shows the usefulness of this technique in overcoming the limitations of previous antibiotic treatment. Right-sided endocarditis occurred classically in young patients (mean age, 36 yr), intravenous drug users in 50% of cases, and suffering more often from embolic complications. Finally, 5 cases without etiology or explaining factors were all immunocompetent male patients with previous aortic valvular lesions, and 3 of the 5 presented with an aortic abscess. Further investigations should be focused on this group to identify new agents of infective endocarditis.

Causative organisms of infective endocarditis according to host status

A prospective study of infective endocarditis (IE) was conducted between 1994 and 2000 in Marseilles, France, and included 170 definite cases diagnosed with the use of modified Duke criteria. Classification of IE based on the aetiological agent was related to epidemiological characteristics, including age, gender and the nature of the injured valve. Enterococci and Streptococcus bovis were identified more frequently in older subjects (p 0.02), and S. bovis was also associated with mitral valve infection (p 0.03). Streptococcus spp. were found to be associated with native valves (p < 10(-3)), whereas coagulase-negative staphylococci and Coxiella burnetii were associated with intracardiac prosthetic material (p < 0.05). S. bovis and Staphylococcus aureus were the predominant species associated with presumably healthy valves (p < 0.05), whereas oral streptococci caused IE exclusively in patients with previous valve damage. The basic host status of IE patients has been linked to specific microorganisms, and this may be of value when empirical treatment is needed in patients who have received previous antibiotic therapy and whose blood cultures are negative.

Q fever endocarditis in the United States

Infections due to Coxiella burnetii, the causative organism of Q fever, are extremely rare in North America. Endocarditis due to the organism has an unusual presentation and poses echocardiographic and laboratory challenges in establishing a diagnosis. We describe the presentation and clinical course of a 40-year-old American man with Q fever endocarditis and briefly discuss the salient issues regarding this entity.

Q fever: a biological weapon in your backyard

Coxiella burnetii, which causes Q fever, is a highly infectious agent that is widespread among livestock around the world. Although the culture process for coxiella is laborious, large amounts of infectious material can be produced. If used as an aerosolised biological weapon, coxiella may not cause high mortality, but could provoke acute disabling disease. In its late course, Q fever can be complicated by fatal (eg, endocarditis) or debilitating (eg, chronic fatigue syndrome) disorders. The diagnosis of Q fever might be delayed because of non-specific and protean presentations. Effective antibiotic treatment is available for the acute form of disease but not for the chronic complications. Vaccination and chemoprophylaxis in selected individuals may be used in the event of bioterrorism.

Coxiella burnetii seropositivity in parturient women is associated with adverse pregnancy outcomes

OBJECTIVE

We conducted a cohort study of parturient women in an area with endemic Q fever infection to determine whether those seropositive for Coxiella burnetii had evidence of adverse birth outcomes.

STUDY DESIGN

From June 1997 to November 1998, the cord blood of all women delivered at our health center was tested for antibodies to C burnetii by indirect immunofluorescence antibody test by using purified whole cell strain Nine Mile antigens. A titer of 1:8 or greater to either phase I or phase II antigens was considered seropositive. Placentas of a sample of cases and seronegative controls had polymerase chain reaction and culture performed.

RESULTS

Evidence of prior infection with C burnetii was found in 3.8% (291/7658) of all parturient women. In a multivariate logistic regression, an association was seen between seropositivity (phase I titer >or= 1:8 or phase II titer >or= 1:32) and newborn gestational age >or=36 weeks (phase I antibody, odds ratio [OR] 2.4, 95% CI 1.3-4.3, P =.005; phase II antibody, OR 1.9, 95% CI 1.02-3.7, P =.04). Women with phase I antibody were more likely to have a prior or current neonatal death (phase I OR 3.2, 95% CI 1.09-9.3, P =.03). No placental samples from 153 seropositive or 93 seronegative women had Q fever by polymerase chain reaction or culture.

CONCLUSION

About 4% of parturient women in this endemic area have evidence of previous exposure to C burnetii and this exposure is associated with adverse pregnancy outcomes. The pathogenesis of this association remains to be determined.

[Prosthetic valve endocarditis due to Coxiella burnetii: six cases]

PURPOSE

Prosthetic valve endocarditis is a dangerous complication of valvular surgery (3-6%). Among involved pathogens, Coxiella burnetii is an occasional agent, though isolated with increasing frequency. We report our experience with this peculiar endocarditis and lay stress on specific diagnostic and therapeutic difficulties.

METHODS

Between 1990 and 1995, six patients retrospectively met the diagnosis criteria for definite endocarditis due to Coxiella burnetii.

RESULTS

Five Algerian men and one French woman presented with prosthetic valve endocarditis with negative blood cultures (on bioprosthesis: four cases, on mechanical valve: two cases). The main clinical and biological feature was febrile congestive heart failure with hepatomegaly, splenomegaly, hepatic and renal abnormalities, inflammatory syndrome, hypergammaglobulinemia, anemia and lymphopenia. Serological testing for Coxiella burnetii provided diagnosis in all cases. Echocardiography displayed vegetations in all cases. Valvular replacement was performed in four patients. With antibiotic therapy including doxycycline or/and hydroxychloroquine, quinolones or rifampicine, all patients experienced complete clinical, biological and echographic remission.

CONCLUSION

Q fever prosthetic valve endocarditis presents as a systemic disorder occurring in patients with valvular heart disease. From now on, early diagnosis and efficient medical treatment may provide permanent prosthetic sterilization.

Q fever 1985-1998. Clinical and epidemiologic features of 1,383 infections

In order to describe the clinical features and the epidemiologic findings of 1,383 patients hospitalized in France for acute or chronic Q fever, we conducted a retrospective analysis based on 74,702 sera tested in our diagnostic center, National Reference Center and World Health Organization Collaborative Center for Rickettsial Diseases. The physicians in charge of all patients with evidence of acute Q fever (seroconversion and/or presence of IgM) or chronic Q fever (prolonged disease and/or IgG antibody titer to phase I of Coxiella burnetii > or = 800) were asked to complete a questionnaire, which was computerized. A total of 1,070 cases of acute Q fever was recorded. Males were more frequently diagnosed, and most cases were identified in the spring. Cases were observed more frequently in patients between the ages of 30 and 69 years. We classified patients according to the different clinical forms of acute Q fever, hepatitis (40%), pneumonia and hepatitis (20%), pneumonia (17%), isolated fever (17%), meningoencephalitis (1%), myocarditis (1%), pericarditis (1%), and meningitis (0.7%). We showed for the first time, to our knowledge, that different clinical forms of acute Q fever are associated with significantly different patient status. Hepatitis occurred in younger patients, pneumonia in older and more immunocompromised patients, and isolated fever was more common in female patients. Risk factors were not specifically associated with a clinical form except meningoencephalitis and contact with animals. The prognosis was usually good except for those with myocarditis or meningoencephalitis as 13 patients died who were significantly older than others. For chronic Q fever, antibody titers to C. burnetii phase I above 800 and IgA above 50 were predictive in 94% of cases. Among 313 patients with chronic Q fever, 259 had endocarditis, mainly patients with previous valvulopathy; 25 had an infection of vascular aneurysm or prosthesis. Patients with endocarditis or vascular infection were more frequently immunocompromised and older than those with acute Q fever. Fifteen women were infected during pregnancy; they were significantly more exposed to animals and gave birth to only 5 babies, only 2 with a normal birth weight. More rare manifestations observed were chronic hepatitis (8 cases), osteoarticular infection (7 cases), and chronic pericarditis (3 cases). Nineteen patients were observed who experienced first a documented acute infection, then, due to underlying conditions, a chronic infection. To our knowledge, we report the largest series of Q fever to date. Our results indicate that Q fever is a protean disease, grossly underestimated, with some of the clinical manifestations being only recently reported, such as Q fever during pregnancy, chronic vascular infection, osteomyelitis, pericarditis, and myocarditis. Our data confirm that chronic Q fever is mainly determined by host factors and demonstrate for the first time that host factors may also play a role in the clinical expression of acute Q fever.

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.

Predominant immunoglobulin A response to phase II antigen of Coxiella burnetii in acute Q fever

Diagnosis of acute Q fever is usually confirmed by serology, on the basis of anti-phase II antigen immunoglobulin M (IgM) titers of >/=1:50 and IgG titers of >/=1:200. Phase I antibodies, especially IgG and IgA, are predominant in chronic forms of the disease. However, between January 1982 and June 1998, we observed anti-phase II antigen IgA titers of >/=1:200 as the sole or main antibody response in 10 of 1,034 (0.96%) patients with acute Q fever for whom information was available. In order to determine whether specific epidemiological or clinical factors were associated with these serological profiles, we conducted a retrospective case-control study that included completion of a standardized questionnaire, which was given to 40 matched controls who also suffered from acute Q fever. The mean age of patients with elevated phase II IgA titers was significantly higher than that usually observed for patients with acute Q fever (P = 0.026); the patients were also more likely than controls to live in rural areas (P = 0.026) and to have increased levels of transaminase in blood (P = 0.03). Elevated IgA titers are usually associated with chronic Q fever and are directed mainly at phase I antigens. Although the significance of our findings is unexplained, we herein emphasize the fact that IgA antibodies are not specific for chronic forms of Q fever and that they may occasionally be observed in patients with acute disease. Moreover, as such antibody profiles may not be determined by most laboratories, which test only for total antibody titers to phase I and II antigens, the three isotype-specific Ig titers should be determined as the first step in diagnosing Q fever.

Q fever endocarditis in Israel and a worldwide review

The worldwide epidemiology and population-based incidence of Q fever endocarditis (QFE) have been less well studied than those for uncomplicated Q fever. An exhaustive literature review revealed 408 patients with QFE reported between 1949 and 1994, mostly from 3 large geographic areas. Underlying valvular heart disease was almost invariably present, and 38% had prosthetic valves. The most common clinical manifestations were fever and congestive heart failure. The mortality rate dropped over the years from 65% to 25%, but a meta-analysis of published data showed the death rate to be significantly lower among patients receiving combination therapy (12/65, 18%), as compared to patients treated with tetracycline alone (18/41, 44%, p = 0.005). A 10-year (1983-1992) retrospective nationwide survey of QFE in Israel revealed 35 patients with QFE, representing an annual incidence of 0.75 cases per 1 million population. Underlying heart disease, clinical manifestations and outcome in the Israeli group were not substantially different from those described in the world literature. The current state-of-the-art clinical approach includes early diagnosis, prompt initiation of combination therapy for at least 3 years, and long-term clinical and serologic follow-up. Adherence to these rules might have contributed to the improved prognosis in recent years.

Seroepidemiology of rickettsial infections in Morocco

The prevalence of antibodies reactive with Rickettsia conorii, Rickettsia typhi, Coxiella burnetii and Ehrlichia chaffeensis was investigated using indirect immunofluorescence (IFA) test on human sera obtained from 300 blood donors in Casablanca and 126 sera obtained from clinical laboratories in Fez. In sera from Casablanca, antibodies reactive at titers > or = 1:32 were found against R. conorii (7%), and R. typhi (1.7%), but not against E. chaffeensis. In the sera from Fez, antibodies were also detected against R. conorii (5.6%), R. typhi (4%), but not against E. chaffeensis. By Western immunoblotting, seroprevalence for R. conorii was in Casablanca and 4.8% in Fez. Antibodies reactive at titers > or = 1:50 against C. burnetii (phase II) were present in sera from Casablanca (1%) and Fez (18.3%).

A new plasmid (QpDV) common to Coxiella burnetii isolates associated with acute and chronic Q fever

Genetic studies of Coxiella burnetii strains suggested the possibility of differentiating new isolates according to their plasmid DNA content. Virulence and/or clinical manifestations ('chronic' and 'acute' Q fever) had been claimed to correlate with this plasmid typing. A new plasmid, named QpDV, was found to be common to C. burnetii isolates obtained from acute and chronic Q fever. According to the results obtained, plasmid usage for detection and differentiation of respective pathovars of C. burnetii and the correlation between gene specificity and pathovar has to be revised. Closer studies suggested a common origin of C. burnetii plasmids, but also showed some differences characteristic for each plasmid, probably reflecting divergent evolution.

Survival of the Q fever agent Coxiella burnetii in the phagolysosome

The Q fever agent, Coxiella burnetii, thrives in the acidic environment of the phagolysosome of the host cell. How this obligate intracellular agent manages to survive within this hostile milieu is unknown; however, several of its enzymes may eliminate or prevent the formation of toxic oxygen metabolites by the host cell. Also implicated as virulence factors are its surface lipopolysaccharide and plasmids.

Q fever serology: cutoff determination for microimmunofluorescence

Q fever, a worldwide zoonosis caused by Coxiella burnetii, lacks clinical specificity and may present as acute or chronic disease. Because of this polymorphism, serological confirmation is necessary to assess the diagnosis. Although microimmunofluorescence is our reference technique, the cutoff titers that are currently used to make a diagnosis of active or chronic Q fever were determined years ago with limited series of patients and sera. We determined the titers of immunoglobulin G (IgG), IgM, and IgA against both phases (I and II) of Coxiella burnetii. Rheumatoid factor was removed before testing IgM and IgA. We report here the various cutoff titers and the kinetics of antibody development from 2,218 first serum samples of patients, among whom 208 suffered from acute Q fever and 53 had chronic Q fever. In active Q fever, we have defined a low cutoff (phase II IgG titer < or = 100) below which the diagnosis cannot be made and would need further confirmation and confirmed a high cutoff (phase II IgG titer > or = 200 and phase II IgM titer > or = 50) over which the diagnosis can be made. For chronic Q fever diagnosis, phase I IgA titers are not contributive despite previous works claiming their usefulness; a phase I IgG titer of > or = 800 is highly predictive (98%) and sensitive (100%). We have also studied the possibility of rejecting or evoking the diagnosis of chronic Q fever by phase II IgG and IgA titers. This method is useful when phase I testing is not available, but the sensitivity remains low (57%).

In vitro activities of ceftriaxone and fusidic acid against 13 isolates of Coxiella burnetii, determined using the shell vial assay

The susceptibilities of 13 isolates of Coxiella burnetii to fusidic acid and ceftriaxone were determined by use of the recently described shell vial assay (D. Raoult, H. Torres, and M. Drancourt, Antimicrob. Agents Chemother, 35:2070-2077, 1991). At a concentration of 4 micrograms/ml, ceftriaxone was bacteriostatic for four isolates and slowed the multiplication of the other nine. Fusidic acid at a concentration of 2 micrograms/ml was bacteriostatic for six isolates and slowed the multiplication of three others. These results show that these compounds could be effective in the phagolysosome of C. burnetii-infected cells.

[Coxiella burnetii endocarditis on a bioprosthetic valve: review of the literature apropos of a case]

A 51-year-old woman, originating from Algeria, developed Q fever endocarditis on porcine bioprosthetic mitral valve. She had chronic course with nonspecific symptoms, such as dyspnea and fever, hepatosplenomegaly, and developed progressive cardiac failure. Worsening of hemodynamic state led to prosthetic valve replacement. Hemocultures were all negative, and the diagnosis of Q fever was unexpectedly performed by systematic screening for specific serum antibody to Coxiella burnetti. High phase I and II specific IgG and IgA antibody titers against C burnetii were found. The patient was treated by doxycycline and ofloxacin, and improved rapidly. Prosthetic valve constitutes likely predisposing factor for the development of chronic Q fever endocarditis. This observation emphasizes the need to search for Q fever in prosthetic valve dysfunction, in particular when hemocultures are negative.

Rapidly fatal Q-fever pneumonia in a patient with chronic granulomatous disease

Acute Q-fever is a systemic illness which rarely has a fatal outcome. Fatal cases do occur with the chronic form of the disease and associated with endocarditis. This report presents the case of a fatal, acute Q-fever pneumonia in an 11-year-old patient with chronic granulomatous disease. Complement fixation antibody titer rose to 1:1,024 with positive IgM in immunofluorescence. Giemsa stained lung sections and indirect immunofluorescence demonstrated the microorganisms in the tissues. The Coxiella burnetii infection was probably contracted during a holiday trip to rural France. Despite the fact that the patient received a variety of antimicrobial agents with broad spectrum activity against bacteria and fungi, coverage for Q-fever, i.e. chloramphenicol or tetracyclines, was not included.

Shell-vial assay: evaluation of a new technique for determining antibiotic susceptibility, tested in 13 isolates of Coxiella burnetii

Coxiella burnetii is a strictly intracellular bacterium. Bacteriostatic effects have been described previously on a few isolates in embryonated eggs (A. J. Spicer, M. G. Peacock, and J. C. Williams, p. 375-383, in W. Burgdorfer and R. L. Anacker, ed., Rickettsiae and rickettsial diseases, 1981). We used the shell-vial technique (D. Raoult, G. Vestris, and M. Enea, J. Clin. Microbiol. 28:2482-2484, 1990) to determine the susceptibility of C. burnetii to amoxicillin, amikacin, erythromycin, co-trimoxazole, pefloxacin, ofloxacin, ciprofloxacin, chloramphenicol, tetracycline, doxycycline, minocycline, and rifampin antibiotics at a single dilution. Human embryonic lung fibroblast monolayers in shell vials were seeded with 13 different C. burnetii isolates, including 3 reference strains (Nine Mile, Q212, and Priscilla) and 10 new isolates, in order to obtain 30% infected cells 6 days later. After inoculation, antibiotics were added, shell vials were incubated for 7 days, and immunofluorescence was revealed and compared with that of the positive controls. Strain Nine Mile was more susceptible than strains Q212 and Priscilla were. The heterogeneity of susceptibility to fluoroquinolones, chloramphenicol, and erythromycin was noted among the strains; all were resistant to amoxicillin and amikacin, and all were susceptible to rifampin, co-trimoxazole, tetracycline, and tetracycline analogs.

Pathogenesis of rickettsial infections emphasis on Q fever

The underlying mechanisms at the organismic, cellular and molecular levels that account for rickettsial pathogenesis are beginning to be revealed. In the case of Coxiella burnetii infection, relatively recent genetic and biochemical data, as well as drug susceptibility studies, indicate a correlation between isolate type and clinical disease--chronic or short-term acute. The use of cultured cells as model host systems has revealed that, indeed, different isolates from the major classified strains of C. burnetii cause different host cell responses. Use of this and other models (guinea pigs, mice) have revealed other characteristics and properties of the rickettsiae and the infected hosts and host cells that may account, in part, for acute disease and persistent infection culminating in chronic disease. The virulence factors involved apparently include the agent's surface lipopolysaccharide; other unidentified factors have not been excluded. Molecular cloning will play a major role in elucidating the roles of these factors and in identifying other virulence determinants.