Coxiella burnetii Endocarditis and Aortic Vascular Graft Infection: An Underrecognized Disease

A Dual-Pathogen Mitral Valve Endocarditis Caused by Coxiella burnetii and Streptococcus gordonii-Which Came First?

Infective endocarditis (IE) is still a life-threatening disease with high morbidity and mortality. While usually caused by a single bacterium, poly-microbial infective endocarditis (IE) is rare. Here, we report a (blood-culture-negative) dual pathogen mitral valve IE caused by Coxiella burnetii and Streptococcus gordonii: A 53-year-old woman was presented to an internal medicine department with abdominal pain for further evaluation. Within the diagnostic work up, transthoracic echocardiography (TTE) revealed an irregularly shaped echogenic mass (5 × 13 mm) adherent to the edge of the posterior mitral valve leaflet and protruding into the left atrium. As infected endocarditis was suspected, blood cultures were initially obtained, but they remained negative. Chronic Q fever infection was diagnosed using serologic testing. After the occurrence of cerebral thromboembolic events, the patient was admitted for mitral valve surgery. Intraoperatively, a massively destructed mitral valve with adhering vegetations was noted. Examination of the mitral valve by broad-range bacterial polymerase chain reaction (PCR) and amplicon sequencing confirmed Coxiella burnetii infection and yielded Streptococcus gordonii as the second pathogen. Based on the detailed diagnosis, appropriate antibiotic therapy of both pathogens was initiated, and the patient could be discharged uneventfully on the 11th postoperative day after a successful minimal-invasive mitral valve replacement.

Coxiella burnetii actively blocks IL-17-induced oxidative stress in macrophages

Coxiella burnetii is a highly infectious pathogen that causes Q fever, a leading cause of culture-negative endocarditis. Coxiella first targets alveolar macrophages and forms a phagolysosome-like compartment called the Coxiella-Containing Vacuole (CCV). Successful host cell infection requires the Type 4B Secretion System (T4BSS), which translocates bacterial effector proteins across the CCV membrane into the host cytoplasm, where they manipulate numerous cell processes. Our prior transcriptional studies revealed that Coxiella T4BSS blocks IL-17 signaling in macrophages. Given that IL-17 is known to protect against pulmonary pathogens, we hypothesize that C. burnetii T4BSS downregulates intracellular IL-17 signaling to evade the host immune response and promote bacterial pathogenesis. Using a stable IL-17 promoter reporter cell line, we confirmed that Coxiella T4BSS blocks IL-17 transcription activation. Assessment of the phosphorylation state of NF-κB, MAPK, and JNK revealed that Coxiella downregulates IL-17 activation of these proteins. Using ACT1 knockdown and IL-17RA or TRAF6 knockout cells, we next determined that IL17RA-ACT1-TRAF6 pathway is essential for the IL-17 bactericidal effect in macrophages. In addition, macrophages stimulated with IL-17 generate higher levels of reactive oxygen species, which is likely connected to the bactericidal effect of IL-17. However, C. burnetii T4SS effector proteins block the IL-17-mediated oxidative stress, suggesting that Coxiella blocks IL-17 signaling to avoid direct killing by the macrophages.

Performance Evaluation and Validation of Air Samplers To Detect Aerosolized Coxiella burnetii

Coxiella burnetii, the etiological agent of Q fever, is an intracellular zoonotic pathogen transmitted via the respiratory route. Once released from infected animals, C. burnetii can travel long distances through air before infecting another host. As such, the ability to detect the presence of C. burnetii in air is important. In this study, three air samplers, AirPort MD8, BioSampler, and the Coriolis Micro, were assessed against a set of predetermined criteria in the presence of three different aerosolized C. burnetii concentrations. Two liquid collection media, phosphate-buffered saline (PBS) and alkaline polyethylene glycol (Alk PEG), were tested with devices requiring a collection liquid. Samples were tested by quantitative polymerase chain reaction assay (qPCR) targeting the single-copy com1 gene or multicopy insertion element IS1111. All air samplers performed well at detecting airborne C. burnetii across the range of concentrations tested. At high nebulized concentrations, AirPort MD8 showed higher, but variable, recovery probabilities. While the BioSampler and Coriolis Micro recovered C. burnetii at lower concentrations, the replicates were far more repeatable. At low and intermediate nebulized concentrations, results were comparable in the trials between air samplers, although the AirPort MD8 had consistently higher recovery probabilities. In this first study validating air samplers for their ability to detect aerosolized C. burnetii, we found that while all samplers performed well, not all samplers were equal. It is important that these results are further validated under field conditions. These findings will further inform efforts to detect airborne C. burnetii around known point sources of infection. IMPORTANCE Coxiella burnetii causes Q fever in humans and coxiellosis in animals. It is important to know if C. burnetii is present in the air around putative sources as it is transmitted via inhalation. This study assessed air samplers (AirPort MD8, BioSampler, and Coriolis Micro) for their efficacy in detecting C. burnetii. Our results show that all three devices could detect aerosolized bacteria effectively; however, at high concentrations the AirPort performed better than the other two devices, showing higher percent recovery. At intermediate and low concentrations AirPort detected at a level higher than or similar to that of other samplers. Quantification of samples was hindered by the limit of quantitation of the qPCR assay. Compared with the other two devices, the AirPort was easier to handle and clean in the field. Testing air around likely sources (e.g., farms, abattoirs, and livestock saleyards) using validated sampling devices will help better estimate the risk of Q fever to nearby communities.

Characteristics of endovascular pneumococcal infections; a decade of nationwide surveillance study

In order to characterize pneumococcal endovascular infection in the post-vaccination era, a retrospective nationwide study based on the Israeli Adult IPD database was conducted. Between 2010 and 2019, 0.6% (23 cases) of IPD cases were of endovascular type, occurring mainly in males (72.3%) with underlying medical conditions (78.2%). Additional pneumococcal source (10 patients) and concomitant infections were not uncommon. Penicillin and ceftriaxone susceptibility rates were 65.2% and 91.3%, respectively; 60.9% of the isolates were not covered by the pneumococcal conjugate vaccine. 21.7% of patients died during hospitalization. In conclusion, pneumococcal endovascular infections still carry significant morbidity and mortality.

Pediatric Q Fever

Purpose of Review

The non-specific presentation of acute Q fever makes it difficult to diagnose in children, but untreated Q fever can result in chronic infections that have severe complications.

Recent Findings

Pediatric Q fever cases continue to be infrequently reported in the literature, and primarily document cases of persistent infections with Coxiella burnetii. Standardized treatment protocols for chronic Q fever in children still do not exist. Doxycycline and hydroxychloroquine are the treatment combination most utilized by healthcare providers to treat Q fever endocarditis or osteomyelitis in children, but a variety of other antibiotic combinations have been reported with varying results. The use of adjunctive therapies, such as such as interferon gamma, has produced mixed outcomes.

Summary

The true impact of Coxiella burnetii on the health of children remains unknown; long-term longitudinal follow-up of children with acute or chronic Q fever has not been reported. Both the acute and chronic forms of Q fever are underreported and underdiagnosed. Healthcare providers should consider Q fever in pediatric patients with culture-negative endocarditis or osteomyelitis.

Cost-effectiveness of Screening Program for Chronic Q Fever, the Netherlands

In the aftermath of a large Q fever (QF) epidemic in the Netherlands during 2007-2010, new chronic QF (CQF) patients continue to be detected. We developed a health-economic decision model to evaluate the cost-effectiveness of a 1-time screening program for CQF 7 years after the epidemic. The model was parameterized with spatial data on QF notifications for the Netherlands, prevalence data from targeted screening studies, and clinical data from the national QF database. The cost-effectiveness of screening varied substantially among subpopulations and geographic areas. Screening that focused on cardiovascular risk patients in areas with high QF incidence during the epidemic ranged from cost-saving to €31,373 per quality-adjusted life year gained, depending on the method to estimate the prevalence of CQF. The cost per quality-adjusted life year of mass screening of all older adults was €70,000 in the most optimistic scenario.

Surveillance for Q Fever Endocarditis in the United States, 1999-2015

Background

Q fever is a worldwide zoonosis caused by Coxiella burnetii. In some persons, particularly those with cardiac valve disease, infection with C. burnetii can cause a life-threatening infective endocarditis. There are few descriptive analyses of Q fever endocarditis in the United States.

Methods

Q fever case report forms submitted during 1999-2015 were reviewed to identify reports describing endocarditis. Cases were categorized as confirmed or probable using criteria defined by the Council for State and Territorial Epidemiologists (CSTE). Demographic, laboratory, and clinical data were analyzed.

Results

Of 140 case report forms reporting endocarditis, 49 met the confirmed definition and 36 met the probable definition. Eighty-two percent were male and the median age was 57 years (range, 16-87 years). Sixty-seven patients (78.8%) were hospitalized, and 5 deaths (5.9%) were reported. Forty-five patients (52.9%) had a preexisting valvulopathy. Eight patients with endocarditis had phase I immunoglobulin G antibody titers >800 but did not meet the CSTE case definition for Q fever endocarditis.

Conclusions

These data summarize a limited set of clinical and epidemiological features of Q fever endocarditis collected through passive surveillance in the United States. Some cases of apparent Q fever endocarditis could not be classified by CSTE laboratory criteria, suggesting that comparison of phase I and phase II titers could be reexamined as a surveillance criterion. Prospective analyses of culture-negative endocarditis are needed to better assess the clinical spectrum and magnitude of Q fever endocarditis in the United States.

Coxiella burnetii Multilevel Disk Space Infection, Epidural Abscess, and Vertebral Osteomyelitis Secondary to Contiguous Spread From Infected Abdominal Aortic Aneurysm or Graft: Report of 4 Cases Acquired in the US and Review of the Literature

Background

Chronic Coxiella burnetii infections such as vertebral osteomyelitis caused by contiguous spread from an infected abdominal aortic graft or aneurysm have been rarely reported and are associated with significant morbidity and mortality.

Methods

We present the first four reported US acquired cases of Coxiella burnetii vertebral osteomyelitis caused by contiguous spread from an infected abdominal aortic graft or aneurysm.

Results

Presenting symptoms included progressive back pain, malaise, and weight loss with recent or remote animal exposure. Typical imaging findings demonstrated a peri-aortic collection with extension to the paraspinal muscles and vertebrae. Antibiotic regimens included doxycycline with either hydroxychloroquine or a quinolone for at least 2 years or as chronic suppression.

Conclusions

C. burnetii vertebral osteomyelitis is rare and can occur by contiguous spread from an abdominal aneurysm or vascular graft infection. It should be suspected in patients where pre-antibiotic cultures are negative with animal/farming exposure.

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.