The diagnostic and clinical utility of microbial cell-free DNA sequencing in a real-world setting

A Committee-Based Diagnostic Stewardship Model for Pathogen Metagenomic Sequencing in Children

BACKGROUND

Metagenomic next-generation sequencing (mNGS) for pathogen detection offers the potential for broad pathogen detection directly from clinical specimens. However, the yield and impact of testing is variable, financial cost is high, and questions surrounding its optimal use remain. Our pediatric institution used a clinical committee-based approach to discuss and approve or deny mNGS test requests. In this study, we evaluate the patient characteristics for which mNGS testing was considered, test yield, and clinical impact of mNGS results when employing this model of diagnostic stewardship.

METHODS

Patients for which plasma cell-free DNA mNGS testing was requested and assessed by the clinical committee between August 1, 2018, and April 30, 2021, were included. The committee discussion emails were used to evaluate reasons for making the test request and treatment plans. Patient characteristics and additional clinical information were gathered by chart review. For approved cases, the clinical impact of the mNGS results were retrospectively adjudicated by infectious disease and clinical microbiology experts.

RESULTS

Twelve requests for plasma cell-free DNA mNGS were evaluated and 9 were approved. mNGS results led to a positive clinical management change in 55% of approved requests. Negative clinical impact of mNGS testing did not occur during the study. The patients for which testing requests were denied had resolution of symptoms without further intervention.

CONCLUSIONS

This committee-based test request approval diagnostic stewardship model has the potential to support high-yield mNGS testing while using healthcare resources responsibly.

Cutaneous legionellosis in an immunocompromised neonate

Cutaneous Legionella infection is rare and primarily seen in immunosuppressed patients. Herein, we present a case of cutaneous and pulmonary legionellosis presenting with fever and erythematous subcutaneous nodules in a neonate with severe combined immunodeficiency. This case underscores the importance of considering this diagnosis and highlights the use of modern testing modalities to promptly diagnose and treat infections in immunocompromised patients.

Pathogen kinetics and detection by next-generation sequencing in pediatric complicated pneumonia

Pediatric pneumonia can be severe and result in empyema. Next-generation sequencing (NGS) may broadly detect pathogens though, optimal timing and impact of sample type on diagnostic yield is unknown. This is a prospective, single-center pilot study of children aged 3 months through 17 years admitted to the PICU with a primary diagnosis of complicated pneumonia. Plasma, endotracheal, nasopharyngeal, and pleural fluid samples were collected at three time points during hospitalization. After nucleic acid extraction, combined libraries were enriched with an NGS enrichment panel kit (RPIP, Illumina), sequenced and quantitative organism detections were analyzed. NGS identified the same bacterial pathogen as traditional testing in all samples, regardless of antibiotic pre-treatment or time collected. Conventional culture methods only identified the pathogen reliably in invasively obtained pleural fluid or endotracheal aspirates. Future application of NGS may allow for non-invasive pathogen detection at a broader range of time points and more targeted antibiotic coverage.

Metagenomic next-generation sequencing in patients with fever of unknown origin: A comprehensive systematic literature review and meta-analysis

Metagenomic Next-Generation Sequencing (mNGS) holds promise in diagnosing fever of unknown origin (FUO) by detecting diverse pathogens. We systematically reviewed the literature to evaluate mNGS's accuracy, clinical efficacy, and limitations in FUO diagnosis. Nine studies revealed mNGS's positivity rate ranging from 66.7% to 93.5% for bacterial bloodstream infections and systemic infections. Meta-analysis of three studies involving 857 patients, including 354 with FUO, showed a sensitivity of 0.91 (95% CI: 0.87-0.93) and specificity of 0.64 (95% CI: 0.58-0.70). Despite lower specificity, mNGS demonstrated a higher Diagnostic Odds Ratio (DOR) of 17.0 (95% CI: 4.5-63.4) compared to conventional microbiological tests (CMTs) at 4.7 (95% CI: 2.9-7.6). While mNGS offers high sensitivity but low specificity in identifying causative pathogens for FUO, its superior DOR suggests potential for more accurate diagnoses and targeted interventions. Further research is warranted to optimize its clinical application in FUO management.

Status check: next-generation sequencing for infectious-disease diagnostics

Next-generation sequencing (NGS) applications for the diagnostics of infectious diseases has demonstrated great potential with three distinct approaches: whole-genome sequencing (WGS), targeted NGS (tNGS), and metagenomic NGS (mNGS, also known as clinical metagenomics). These approaches provide several advantages over traditional microbiologic methods, though challenges still exist.

A decade of clinical microbiology: top 10 advances in 10 years: what every infection preventionist and antimicrobial steward should know

The past 10 years have brought paradigm-shifting changes to clinical microbiology. This paper explores the top 10 transformative innovations across the diagnostic spectrum, including not only state of the art technologies but also preanalytic and post-analytic advances. Clinical decision support tools have reshaped testing practices, curbing unnecessary tests. Innovations like broad-range polymerase chain reaction and metagenomic sequencing, whole genome sequencing, multiplex molecular panels, rapid phenotypic susceptibility testing, and matrix-assisted laser desorption ionization time-of-flight mass spectrometry have all expanded our diagnostic armamentarium. Rapid home-based testing has made diagnostic testing more accessible than ever. Enhancements to clinician-laboratory interfaces allow for automated stewardship interventions and education. Laboratory restructuring and consolidation efforts are reshaping the field of microbiology, presenting both opportunities and challenges for the future of clinical microbiology laboratories. Here, we review key innovations of the last decade.

The Value of Next-Generation Sequencing in Diagnosis and Therapy of Critically Ill Patients with Suspected Bloodstream Infections: A Retrospective Cohort Study

Bloodstream infection (BSI), a frequent cause of severe sepsis, is a life-threatening complication in critically ill patients and still associated with a high mortality rate. Rapid pathogen identification from blood is crucial for an early diagnosis and the treatment of patients with suspected BSI. For this purpose, novel diagnostic tools on the base of genetic analysis have emerged for clinical application. The aim of this study was to assess the diagnostic value of additional next-generation sequencing (NGS) pathogen test for patients with suspected BSI in a surgical ICU and its potential impact on antimicrobial therapy. In this retrospective single-centre study, clinical data and results from blood culture (BC) and NGS pathogen diagnostics were analysed for ICU patients with suspected BSI. Consecutive changes in antimicrobial therapy and diagnostic procedures were evaluated. Results: 41 cases with simultaneous NGS and BC sampling were assessed. NGS showed a statistically non-significant higher positivity rate than BC (NGS: 58.5% (24/41 samples) vs. BC: 21.9% (9/41); p = 0.056). NGS detected eight different potentially relevant bacterial species, one fungus and six different viruses, whereas BC detected four different bacterial species and one fungus. NGS results affected antimicrobial treatment in 7.3% of cases. Conclusions: NGS-based diagnostics have the potential to offer a higher positivity rate than conventional culture-based methods in patients with suspected BSI. Regarding the high cost, their impact on anti-infective therapy is currently limited. Larger randomized prospective clinical multicentre studies are required to assess the clinical benefit of this novel diagnostic technology.

Clinical utility of plasma microbial cell-free DNA sequencing in determining microbiologic etiology of infectious syndromes in solid organ transplant recipients

Background

Metagenomic next-generation sequencing (mNGS) is increasingly being used for microbial detection in various infectious syndromes. However, data regarding the use of mNGS in solid organ transplant recipients (SOTR) are lacking.

Objectives

To describe and analyze real-world clinical impact of mNGS using plasma microbial cell-free DNA (mcfDNA) in SOTR.Design: Retrospectively reviewed all adult SOTR who underwent mNGS testing using plasma mcfDNA at Baylor St Luke's Medical Center from March 2017 to February 2023.

Methods

Clinical impact (positive, neutral, and negative) was assessed using standardized objective criteria. Three Infectious Diseases physicians independently performed clinical adjudication to determine the correlation of mcfDNA results with clinical diagnosis. A descriptive analysis of the patient and clinical characteristics was performed.

Results

A total of 113 mcfDNA tests in liver (42%), kidney (35%), lung (20%) and heart (13%) transplant recipients were performed in the study period. The most common clinical syndromes were pneumonia (36%), fever of unknown origin (16%), and intra-abdominal infections (15%). Most (80, 71%) of the mcfDNA test results were positive for microorganisms. Twenty-seven (24%) cases were classified as positive clinical impact, 82 (73%) were neutral and 4 (3%) were negative, respectively.

Conclusion

In SOTR, mcfDNA sequencing can add a positive clinical impact in a quarter of the cases and identify microorganisms beyond conventional microbiological testing across clinical syndromes. The negative clinical impact was rare. However, larger prospective studies are needed to define the optimal timing and utilization of mcfDNA in the sequence of diagnostic evaluation for syndrome-specific workup in SOTR.

Summary

Metagenomic next-generation sequencing (mNGS) is a novel diagnostic tool that can identify difficult-to-detect microorganisms in SOTR. Our study demonstrates that the mNGS test resulted in a positive clinical impact in 1 out of 4 patients.