Plasma metagenomic next-generation sequencing of microbial cell-free DNA detects pathogens in patients with suspected infected pancreatic necrosis

Diagnostic performance of the DISQVER metagenomic sequencing tool for the identification of pathogens in febrile neutropenic patients: the ADNEMIA trial

INTRODUCTION

While intensive protocols in onco-haematology have improved survival rates for patients with haematological malignancies, they have also resulted in an increased incidence of infection associated with therapy-induced immunosuppression (including chemotherapy-induced febrile neutropenia; FN). The occurrence of FN, associated with high morbidity and mortality, necessitates broad-spectrum antibiotic therapy, occasioning delayed chemotherapy and resulting in a loss of opportunity for the patient. Considering that without an identified pathogen, a 10% mortality rate can ensue, documentation is essential to the optimisation of antibiotic therapy. However, blood culture (the reference test) is limited for several reasons: such as fastidious culture, antibiotic treatment prior to sampling or insufficient sample volume. Sequencing technologies have led to the development of diagnostic approaches based on the detection of circulating DNA in blood. This study will aim to assess the clinical utility of metagenomic next-generation sequencing (mNGS)-DISQVER technology in detecting pathogenic microorganisms from blood samples of patients undergoing high-risk FN treatment.

METHODS AND ANALYSIS

This nationwide, prospective, multicentre, interventional, proof-of-concept clinical trial will enrol 200 patients. Will include patients≥18 years old, treated for malignancy, at high risk of FN (Multinational Association for Supportive Care in Cancer score≤21) with an expected duration of neutropenia≥7 days. Patients who received antibiotic treatment within 24 hours prior to enrolment, have previously participated and/or have enhanced protection will be excluded. The primary outcome will be determined by considering the microorganisms responsible for this FN, weighted by the assessment of an adjudication committee. Secondary outcomes will evaluate patient management depending on the arm. The second secondary outcome will be determined by the duration of conventional assessment, frequency of microorganisms detected during routine care and percentage distribution of theoretical adjustments made to anti-infective treatment based on microorganisms diagnosed using the mNGS-DISQVER tool as compared with conventional practices. Identifying the pathogens responsible for high-risk FN from a blood sample, using an unbiased technique, can provide microbiological documentation and may even reveal unexpected microorganisms in these profoundly immunocompromised patients.

ETHICS AND DISSEMINATION

The protocol received approval from the Comité de Protection des Personnes Sud-Méditerranée II. All participants will provide informed consent before participation. The trial has been registered on ClinicalTrials.gov (identifier NCT06075888). The results of the main trial and each of the secondary endpoints will be submitted for publication in a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov NCT06075888.

Application of metagenomic next-generation sequencing in the diagnosis of infectious diseases

Metagenomic next-generation sequencing (mNGS) is a transformative approach in the diagnosis of infectious diseases, utilizing unbiased high-throughput sequencing to directly detect and characterize microbial genomes from clinical samples. This review comprehensively outlines the fundamental principles, sequencing workflow, and platforms utilized in mNGS technology. The methodological backbone involves shotgun sequencing of total nucleic acids extracted from diverse sample types, enabling simultaneous detection of bacteria, viruses, fungi, and parasites without prior knowledge of the infectious agent. Key advantages of mNGS include its capability to identify rare, novel, or unculturable pathogens, providing a more comprehensive view of microbial communities compared to traditional culture-based methods. Despite these strengths, challenges such as data analysis complexity, high cost, and the need for optimized sample preparation protocols remain significant hurdles. The application of mNGS across various systemic infections highlights its clinical utility. Case studies discussed in this review illustrate its efficacy in diagnosing respiratory tract infections, bloodstream infections, central nervous system infections, gastrointestinal infections, and others. By rapidly identifying pathogens and their genomic characteristics, mNGS facilitates timely and targeted therapeutic interventions, thereby improving patient outcomes and infection control measures. Looking ahead, the future of mNGS in infectious disease diagnostics appears promising. Advances in bioinformatics tools and sequencing technologies are anticipated to streamline data analysis, enhance sensitivity and specificity, and reduce turnaround times. Integration with clinical decision support systems promises to further optimize mNGS utilization in routine clinical practice. In conclusion, mNGS represents a paradigm shift in the field of infectious disease diagnostics, offering unparalleled insights into microbial diversity and pathogenesis. While challenges persist, ongoing technological advancements hold immense potential to consolidate mNGS as a pivotal tool in the armamentarium of modern medicine, empowering clinicians with precise, rapid, and comprehensive pathogen detection capabilities.

Appropriate Use of Antibiotics in Acute Pancreatitis: A Scoping Review

BACKGROUND

While selective use of antibiotics for infected pancreatic necrosis (IPN) in acute pancreatitis (AP) is recommended, studies indicate a high rate of inadequate treatment.

METHODS

A search of PubMed, Scopus, and Cochrane databases was conducted, focusing on primary research and meta-analyses. Data were categorized based on core concepts, and a narrative synthesis was performed.

RESULTS

The search identified a total of 1016 publications. After evaluating 203 full texts and additional sources from the grey literature, 80 studies were included in the review. The answers obtained were: (1) Preventive treatment does not decrease the incidence of IPN or mortality. Given the risks of bacterial resistance and fungal infections, antibiotics should be reserved for highly suspected or confirmed IPN; (2) The diagnosis of IPN does not always require microbiological samples, as clinical suspicion or computed tomography signs can suffice. Early diagnosis and treatment may be improved by using biomarkers such as procalcitonin and novel microbiological methods; (3) When indicated, early initiation of antibiotics is a key determinant in reducing mortality associated with IPN; (4) Antibiotics with good penetration into pancreatic tissue covering Gram-negative and Gram-positive bacteria should be used. Routine antifungal therapy is not recommended; (5) The step-up approach, including antibiotics, is the standard for IPN management; (6) Antibiotic duration should be kept to a minimum and should be based on the quality of source control and patient condition.

CONCLUSIONS

Early antibiotic therapy is essential for the treatment of IPN, but prophylactic antibiotics are not recommended in AP. High-quality randomized controlled trials are required to better understand the role of antibiotics and antifungals in AP management.

Metagenomic Next-Generation Sequencing-Based Fine-Needle Aspiration in Patients With Suspected Infected Pancreatic Necrosis

INTRODUCTION

Fine-needle aspiration (FNA) is no longer recommended for diagnosing infected pancreatic necrosis (IPN) due to a high false-negative rate. Metagenomic next-generation sequencing (mNGS) is a valuable tool for identifying potential pathogens. We hypothesized that adding mNGS to the standard FNA procedure may increase diagnostic accuracy.

METHODS

This is a prospective, single-arm feasibility study enrolling patients with acute necrotizing pancreatitis complicated by suspected IPN. Computed tomography-guided FNA was performed immediately after enrollment, and the drainage samples were subjected to culture and mNGS assays simultaneously. Confirmatory IPN within the following week of the index FNA procedure was the reference standard. The diagnostic performance of FNA-mNGS and the impact of mNGS results on treatment were evaluated. Historical controls were used for comparison of clinical outcomes.

RESULTS

There was no significant difference between mNGS and culture in the positive rate (75% vs 70%, P = 0.723). The accuracy of FNA-mNGS was 80.0%, with a sensitivity of 82.35%, specificity of 66.67%, positive predictive value of 93.3%, and negative predictive value of 40.0%. The results of the mNGS led to treatment change in 16 of 20 patients (80%), including implementing percutaneous catheter drainage (n = 7), expanding antibiotic coverage (n = 2), percutaneous catheter drainage and expanding coverage (n = 4), narrowing antibiotic coverage (n = 1), and discontinuation of antibiotics (n = 2). The FNA-mNGS approach was not associated with improved clinical outcomes compared with the historical control group.

DISCUSSION

The addition of mNGS to standard FNA has comparable diagnostic accuracy with culture-based FNA and may not be associated with improved clinical outcomes.

Evaluation of the diagnostic utility of metagenomic next-generation sequencing testing for pathogen identification in infected hosts: a retrospective cohort study

Background

Metagenomic next-generation sequencing (mNGS) testing identifies thousands of potential pathogens in a single blood test, though data on its real-world diagnostic utility are lacking.

Objectives

Determine the diagnostic utility of mNGS testing in practice and factors associated with high clinical utility.

Design

Retrospective cohort study of mNGS tests ordered from June 2018 through May 2020 at a community teaching hospital.

Methods

Tests were included if ordered for diagnostic purposes in patients with probable or high clinical suspicion of infection. Exclusions included patient expiration, hospice care, or transfer outside of the institution. Utility criteria were established a priori by the research team. Two investigators independently reviewed each test and categorized it to either high or low diagnostic utility. Reviewer discordance was referred to a third investigator. The stepwise multiple regression method was used to identify clinical factors associated with high diagnostic utility.

Results

Among 96 individual tests from 82 unique patients, 80 tests met the inclusion criteria for analysis. At least one potential pathogen was identified in 58% of tests. Among 112 pathogens identified, there were 74 bacteria, 25 viruses, 12 fungi, and 1 protozoon. In all, 46 tests (57.5%) were determined to be of high diagnostic utility. Positive mNGS tests were identified in 36 (78.3%) and 11 (32.4%) of high and low diagnostic utility tests, respectively (p < 0.001). Antimicrobials were changed after receiving test results in 31 (67.4%) of high utility tests and 4 (11.8%) of low utility tests (p < 0.0001). In the multiple regression model, a positive test [odds ratio (OR) = 10.9; 95% confidence interval (CI), 3.2-44.4] and consultation with the company medical director (OR = 3.6; 95% CI, 1.1-13.7) remained significantly associated with high diagnostic utility.

Conclusion

mNGS testing resulted in high clinical utility in most cases. Positive mNGS tests were associated with high diagnostic utility. Consultation with the Karius® medical director is recommended to maximize utility.

Circulating Microbial Cell-Free DNA in Health and Disease

Human blood contains low biomass of circulating microbial cell-free DNA (cfmDNA) that predominantly originates from bacteria. Numerous studies have detected circulating cfmDNA in patients with infectious and non-infectious diseases, and in healthy individuals. Remarkable differences were found in the microbial composition of healthy subjects and patients compared to cohorts with various diseases or even patients with diversified prognoses, implying that these alterations may be associated with disease development. Although the function of circulating cfmDNA needs to be elucidated (whether it acts as a bystander of dysbiosis or a key player in disease development), several studies have demonstrated its potential as a non-invasive biomarker that may improve diagnosis and treatment efficacy. The origin of circulating cfmDNA is still the subject of much deliberation, but studies have identified members of various microbiome niches, including the gut, oral cavity, airways, and skin. Further studies investigating the origin and function of circulating cfmDNA are needed. Moreover, low-biomass microbiome studies are prone to contamination, therefore stringent negative experimental control reactions and decontamination frameworks are advised in order to detect genuine circulating cfmDNA.

Fragment Ends of Circulating Microbial DNA as Signatures for Pathogen Detection in Sepsis

BACKGROUND

Nuclear-derived cell-free DNA (cfDNA) molecules in blood plasma are nonrandomly fragmented, bearing a wealth of information related to tissues of origin. DNASE1L3 (deoxyribonuclease 1 like 3) is an important player in shaping the fragmentation of nuclear-derived cfDNA molecules, preferentially generating molecules with 5 CC dinucleotide termini (i.e., 5 CC-end motif). However, the fragment end properties of microbial cfDNA and its clinical implication remain to be explored.

METHODS

We performed end motif analysis on microbial cfDNA fragments in plasma samples from patients with sepsis. A sequence context-based normalization method was used to minimize the potential biases for end motif analysis.

RESULTS

The end motif profiles of microbial cfDNA appeared to resemble that of nuclear cfDNA (Spearman correlation coefficient: 0.82, P value 0.001). The CC-end motif was the most preferred end motif in microbial cfDNA, suggesting that DNASE1L3 might also play a role in the fragmentation of microbe-derived cfDNA in plasma. Of note, differential end motifs were present between microbial cfDNA originating from infection-causing pathogens (enriched at the CC-end) and contaminating microbial DNA potentially derived from reagents or the environment (nearly random). The use of fragment end signatures allowed differentiation between confirmed pathogens and contaminating microbes, with an area under the receiver operating characteristic curve of 0.99. The performance appeared to be superior to conventional analysis based on microbial cfDNA abundance alone.

CONCLUSIONS

The use of fragmentomic features could facilitate the differentiation of underlying contaminating microbes from true pathogens in sepsis. This work demonstrates the potential usefulness of microbial cfDNA fragmentomics in metagenomics analysis.