Coxiella burnetii and Bartonella Endocarditis Diagnosed by Metagenomic Next-Generation Sequencing

Infective endocarditis caused by Streptococcus sinensis diagnosed with next-generation sequencing: a case report and literature review

BACKGROUND

Infective endocarditis (IE) caused by Streptococcus sinensis is rare and challenging to diagnose due to the irregular use of antibiotics and the limitations of conventional diagnostic methods. Metagenomaic next-generation sequencing (mNGS) has emerged as a valuable diagnostic tool, offering significantly enhanced accuracy in identifying elusive pathogens, particularly in blood culture-negative endocarditis (BCNE).

CASE PRESENTATION

We reported the case of a 33-year-old male who presented with recurrent intermittent fever lasting over six months. Despite multiple diagnostic attempts, including blood cultures, no causative pathogen was identified. Blood mNGS revealed the presence of S. sinensis, a rare pathogen associated with IE. Echocardiography confirmed vegetation on the mitral and aortic valves, leading to a possible diagnosis of IE. The patient underwent successful surgical valve replacement, and subsequent mNGS of excised valve tissue confirmed the presence of S. sinensis. We administered a tailored antibiotic regimen, and the patient achieved a favorable recovery with no significant complications during follow-up.

RESULTS

We identified 11 additional cases of S. sinensis-induced IE through a literature review, including patients from diverse geographic regions and age groups. Most cases were associated with prior dental procedures or poor oral health. Common diagnostic methods included blood culture and 16 S rRNA sequencing, while recent cases utilized mNGS. Treatment typically involved penicillin-based antibiotics combined with gentamicin, with surgical intervention in most cases leading to favorable outcomes.

CONCLUSIONS

This case highlights the diagnostic value of mNGS in identifying pathogens in IE, particularly when traditional methods fail due to prior antibiotic use. While mNGS has significant advantages in pathogen detection, it cannot replace standard microbiological techniques and should be considered a complementary approach. Integrating mNGS into clinical workflows can improve diagnostic accuracy, especially in BCNE cases, and guide effective treatment strategies.

CLINICAL TRIAL NUMBER

Not applicable.

A case of stroke as a unique sign of subclinical infective endocarditis by Abiotrophia defectiva: a case report

PURPOSE

Here we describe a patient admitted for a stroke that was unexpectedly correlated with subclinical infective endocarditis attributable to a rarely opportunistic pathogen, Abiotrophia defectiva.

CASE REPORT

A 75-year-old man presented with a stroke. Transesophageal echocardiography suggested vegetation on all aortic valve cusps, despite the absence of clinical or laboratory signs of infection. Surprisingly, three sets of blood cultures collected without fever were positive for A. defectiva. Although the patient did not exhibit classic signs of infection during hospitalization, the severity of the valve condition necessitated replacement with a bioprosthesis.

CONCLUSIONS

This clinical case underscores the importance of investigating the infective origin of endocarditis, even in the absence of clinical or laboratory evidence. Physicians should maintain a high level of suspicion, especially in patients with highly suggestive anamnestic characteristics.

Case report: A case of blood culture-negative Bartonella quintana endocarditis: blood mNGS is an efficient method for early diagnosis

Bartonella quintana is one of the main causes of blood culture-negative endocarditis, and routine blood culture and serological methods are difficult to achieve early diagnosis. We report a case of blood culture-negative Bartonella quintana endocarditis from southwestern Chongqing. The patient was a 67-year-old male scavenger who presented with heart failure without fever as the main clinical manifestation upon admission. He stated having had contact with stray cats in the past 2 months. The combination of clinical symptoms, echocardiography, and blood mNGS testing confirmed the infection of Bartonella quintana.

Diagnostic performance of metagenomic sequencing in patients with suspected infection: a large-scale retrospective study

Background

Metagenomic next-generation sequencing (mNGS) has been widely reported to identify pathogens in infectious diseases (IDs). In this work, we intended to investigate the diagnostic value and clinical acceptance of paired-samples mNGS as compared to the culture method.

Methods

A total of 361 patients with suspected infection were retrospectively included. With reference to the clinical diagnosis, we compared the diagnostic performance and clinical acceptance in pathogen detection between mNGS and culture tests. Moreover, the pathogen concordance of paired blood and respiratory tract (RT) samples in mNGS assay was investigated.

Results

Among 511 samples, 62.04% were shown to be pathogen positive by mNGS, and that for clinical diagnosis was 51.86% (265/511). When compared to culture assay (n = 428), mNGS had a significantly higher positivity rate (51.87% vs. 33.18%). With reference to the clinical diagnosis, the sensitivity of mNGS outperformed that of culture (89.08% vs. 56.72%). Importantly, mNGS exhibited a clinically accepted rate significantly superior to that of culture. In addition, the mNGS result from 53 paired blood and RT samples showed that most pairs were pathogen positive by both blood and RT, with pathogens largely being partially matched.

Conclusion

Through this large-scale study, we further illustrated that mNGS had a clinically accepted rate and sensitivity superior to those of the traditional culture method in diagnosing infections. Moreover, blood and paired RT samples mostly shared partial-matched positive pathogens, especially for pathogens with abundant read numbers in RT, indicating that both blood and RT mNGS can aid the identification of pathogens for respiratory system infection.

Emerging and Re-Emerging Pathogens in Valvular Infective Endocarditis: A Review

Infective endocarditis (IE) is a microbial infection of the endocardial surface, most commonly affecting native and prosthetic valves of the heart. The epidemiology and etiology of the disease have evolved significantly over the last decades. With a growing elderly population, the incidence of degenerative valvopathies and the use of prosthetic heart valves have increased, becoming the most important predisposing risk factors. This change in the epidemiology has caused a shift in the underlying microbiology of the disease, with Staphylococci overtaking Streptococci as the main causative pathogens. Other rarer microbes, including Streptococcus agalactiae, Pseudomonas aeruginosa, Coxiella burnetti and Brucella, have also emerged or re-emerged. Valvular IE caused by these pathogens, especially Staphylococcus aureus, is often associated with a severe clinical course, leading to high rates of morbidity and mortality. Therefore, prompt diagnosis and management are crucial. Due to the high virulence of these pathogens and an increased incidence of antimicrobial resistances, surgical valve repair or replacement is often necessary. As the epidemiology and etiology of valvular IE continue to evolve, the diagnostic methods and therapies need to be progressively advanced to ensure satisfactory clinical outcomes.

Understanding Bartonella-Associated Infective Endocarditis: Examining Heart Valve and Vegetation Appearance and the Role of Neutrophilic Leukocytes

BACKGROUND

The endocardium and cardiac valves undergo severe impact during infective endocarditis (IE), and the formation of vegetation places IE patients at a heightened risk of embolic complications and mortality. The relevant literature indicates that 50% of IE cases exhibit structurally normal cardiac valves, with no preceding history of heart valve disease. Gram-positive cocci emerge as the predominant causative microorganisms in IE, while Gram-negative Bartonella spp., persisting in the endothelium, follow pathogenic pathways distinct from those of typical IE-causing agents. Employing clinical as well as advanced microbiological and molecular assays facilitated the identification of causative pathogens, and various morphological methods were applied to evaluate heart valve damage, shedding light on the role of neutrophilic leukocytes in host defense. In this research, the immunohistochemical analysis of neutrophilic leukocyte activation markers such as myeloperoxidase, neutrophil elastase, calprotectin, and histone H3, was performed. A distinct difference in the expression patterns of these markers was observed when comparing Bartonella spp.-caused and non-Bartonella spp.-caused IE. The markers exhibited significantly higher expression in non-Bartonella spp.-caused IE compared to Bartonella spp.-caused IE, and they were more prevalent in vegetation than in the valvular leaflets. Notably, the expression of these markers in all IE cases significantly differed from that in control samples. Furthermore, we advocated the use of 16S rRNA Next-Generation Sequencing on excised heart valves as an effective diagnostic tool for IE, particularly in cases where blood cultures yielded negative results. The compelling results achieved in this study regarding the enigmatic nature of Bartonella spp. IE's pathophysiology contribute significantly to our understanding of the peculiarities of inflammation and immune responses.

Impact of Metagenomic Next-Generation Sequencing of Plasma Cell-free DNA Testing in the Management of Patients With Suspected Infectious Diseases

Metagenomic next-generation sequencing (mNGS) of cell-free DNA is an emerging modality for the diagnosis of infectious diseases, but studies on its clinical utility are limited. We conducted a retrospective single-center study including all patients who had plasma mNGS sent at the University of Michigan between 1 January 2021 and 25 July 2022. Test results were assessed for clinical impact. A total of 71 tests were sent on 69 patients; the mean ± SD age was 52 ± 19 years; and 35% of patients were immunocompromised. Forty-five (63%) mNGS test results were positive and 14 (31%) had clinical impact-from starting new antimicrobials (n = 7), discontinuing antimicrobials (n = 4), or changing antimicrobial duration (n = 2) or by affecting surgical decision making (n = 1). Twenty-six (37%) mNGS test results were negative and only 4 (15%) were impactful, leading to discontinuation of antimicrobials. Overall, just 25% of mNGS tests were clinically relevant. There was no significant difference in the proportion of tests that were clinically relevant between negative and positive results (P = .16) or if patients were immunocompromised (P = .57). Plasma mNGS was most frequently impactful (in 50% of patients) when included in the diagnostic workup of cardiovascular infection but less impactful in other clinical syndromes, including fever of unknown origin and pulmonary infection. Our findings underscore the need to further study this testing modality, particularly with prospective research including negative controls, before it is considered for widespread use.