Microbial Cell-free DNA Sequencing Research Articles

The role of microbial cell free DNA sequencing in sepsis detection in the neonate.

The role of microbial cell free DNA sequencing in sepsis detection in the neonate.

Analytical and clinical validation of direct detection of antimicrobial resistance markers by plasma microbial cell-free DNA sequencing.

This manuscript is ideally suited for the Innovative Diagnostic Methods sections as it reports the analytical and clinical validation of a novel application of plasma microbial cell-free DNA sequencing for direct detection of seven selected antimicrobial resistance markers in 18 target pathogens. Clearly, it has potential clinical utility in optimizing therapy and was incorporated into the Karius test workflow in September 2023. In addition, the workflow could readily be adapted to expand the number of target bacteria and antimicrobial resistance markers as needed.

Clinical Utility of Plasma Microbial Cell-Free DNA Sequencing Among Immunocompromised Patients With Pneumonia.

Plasma microbial cell-free DNA (mcfDNA) sequencing can establish the etiology of multiple infectious syndromes by identifying microbial DNA in plasma. However, data are needed to define the clinical scenarios where this tool offers the highest clinical benefit. We conducted a prospective multicenter observational study that evaluated the impact of plasma mcfDNA sequencing compared with usual care testing among adults with hematologic malignancies. This is a secondary analysis of an expanded cohort that evaluated the clinical utility of plasma mcfDNA sequencing across prespecified and adjudicated outcomes. We examined the percentage of participants for whom plasma mcfDNA sequencing identified a probable cause of pneumonia or clinically relevant nonpneumonia infection. We then assessed potential changes in antimicrobial therapy based on plasma mcfDNA sequencing results and the potential for early mcfDNA testing to avoid bronchoscopy and its associated adverse events. Of 223 participants, at least 1 microbial detection by plasma mcfDNA sequencing was adjudicated as a probable cause of pneumonia in 57 (25.6%) and a clinically relevant nonpneumonia infection in 88 (39.5%). A probable cause of pneumonia was exclusively identified by plasma mcfDNA sequencing in 23 (10.3%) participants. Antimicrobial therapy would have changed for 41 (18.4%) participants had plasma mcfDNA results been available in real time. Among the 57 participants with a probable cause of pneumonia identified by plasma mcfDNA sequencing, bronchoscopy identified no additional probable cause of pneumonia in 52 (91.2%). Plasma mcfDNA sequencing could improve management of both pneumonia and other concurrent infections in immunocompromised patients with suspected pneumonia.

Utility of Serial Microbial Cell-free DNA Sequencing for Inpatient and Outpatient Pathogen Surveillance Among Allogeneic Hematopoietic Stem Cell Transplant Recipients.

This study characterizes the clinical utility and validity of the Karius test (KT), a plasma microbial cell-free DNA sequencing platform, as an infection surveillance tool among hematopoietic stem cell transplant (HCT) recipients, including monitoring for cytomegalovirus (CMV) and detecting infections relative to standard microbiologic testing (SMT). A prospective, observational cohort study was performed among adult HCT recipients as inpatients and outpatients. Serial KTs were performed starting with 1 sample within 14 days before HCT, then weekly from 7-63 days posttransplant then monthly from 3-12 months post-HCT. Diagnostic performance of KT versus CMV polymerase chain reaction was evaluated with positive percent agreement and negative percent agreement. Infectious events (<12 months post-HCT) were extracted from medical records. For infectious events without positive SMT, 2 clinicians adjudicated KT results to determine if any detections were a probable cause. Difference in time from KT pathogen detection and infection onset was calculated. Of the 70 participants, mean age was 49.9 years. For CMV surveillance, positive percent agreement was 100% and negative percent agreement was 90%. There was strong correlation between CMV DNA and KT molecules per microliter (r 2: 0.84, P < .001). Of the 32 SMT+/KT+ infectious events, KT identified 26 earlier than SMT (median: -12 days) and an additional 5 diagnostically difficult pathogens identified by KT but not SMT. KT detected CMV with high accuracy and correlation with quantitative polymerase chain reaction. Among infectious events, KT demonstrated additive clinical utility by detecting pathogens earlier than SMT and those not detected by SMT.

Cost-Effectiveness of Plasma Microbial Cell-Free DNA Sequencing When Added to Usual Care Diagnostic Testing for Immunocompromised Host Pneumonia.

Immunocompromised host pneumonia (ICHP) is an important cause of morbidity and mortality, yet usual care (UC) diagnostic tests often fail to identify an infectious etiology. A US-based, multicenter study (PICKUP) among ICHP patients with hematological malignancies, including hematological cell transplant recipients, showed that plasma microbial cell-free DNA (mcfDNA) sequencing provided significant additive diagnostic value. The objective of this study was to perform a cost-effectiveness analysis (CEA) of adding mcfDNA sequencing to UC diagnostic testing for hospitalized ICHP patients. A semi-Markov model was utilized from the US third-party payer's perspective such that only direct costs were included, using a lifetime time horizon with discount rates of 3% for costs and benefits. Three comparators were considered: (1) All UC, which included non-invasive (NI) and invasive testing and early bronchoscopy; (2) All UC & mcfDNA; and (3) NI UC & mcfDNA & conditional UC Bronch (later bronchoscopy if the initial tests are negative). The model considered whether a probable causative infectious etiology was identified and if the patient received appropriate antimicrobial treatment through expert adjudication, and if the patient died in-hospital. The primary endpoints were total costs, life-years (LYs), equal value life-years (evLYs), quality-adjusted life-years (QALYs), and the incremental cost-effectiveness ratio per QALY. Extensive scenario and probabilistic sensitivity analyses (PSA) were conducted. At a price of $2000 (2023 USD) for the plasma mcfDNA, All UC & mcfDNA was more costly ($165,247 vs $153,642) but more effective (13.39 vs 12.47 LYs gained; 10.20 vs 9.42 evLYs gained; 10.11 vs 9.42 QALYs gained) compared to All UC alone, giving a cost/QALY of $16,761. NI UC & mcfDNA & conditional UC Bronch was also more costly ($162,655 vs $153,642) and more effective (13.19 vs 12.47 LYs gained; 9.96 vs 9.42 evLYs gained; 9.96 vs 9.42 QALYs gained) compared to All UC alone, with a cost/QALY of $16,729. The PSA showed that above a willingness-to-pay threshold of $50,000/QALY, All UC & mcfDNA was the preferred scenario on cost-effectiveness grounds (as it provides the most QALYs gained). Further scenario analyses found that All UC & mcfDNA always improved patient outcomes but was not cost saving, even when the price of mcfDNA was set to $0. Based on the evidence available at the time of this analysis, this CEA suggests that mcfDNA may be cost-effective when added to All UC, as well as in a scenario using conditional bronchoscopy when NI testing fails to identify a probable infectious etiology for ICHP. Adding mcfDNA testing to UC diagnostic testing should allow more patients to receive appropriate therapy earlier and improve patient outcomes.

A Machine learning model for predicting sepsis based on an optimized assay for microbial cell-free DNA sequencing

ObjectiveTo integrate an enhanced molecular diagnostic technique to develop and validate a machine-learning model for diagnosing sepsis. MethodsWe prospectively enrolled patients suspected of sepsis from August 2021 to August 2023. Various feature selection algorithms and machine learning models were used to develop the model. The best classifier was selected using 5-fold cross validation set and then was applied to assess the performance of the model in the testing set. Additionally, we employed the Shapley Additive exPlanations (SHAP) method to illustrate the effects of the features. ResultsWe established an optimized mNGS assay and proposed using the copies of microbe-specific cell-free DNA per milliliter of plasma (CPM) as the detection signal to evaluate the real burden, with strong precision and high accuracy. In total, 237 patients were eligible for participation, which were randomly assigned to either the training set (70 %, n = 165) or the testing set (30 %, n = 72). The random forest classifier achieved accuracy, AUC and F1 scores of 0.830, 0.918 and 0.856, respectively, outperforming other machine learning models in the training set. Our model demonstrated clinical interpretability and achieved good prediction performance in differentiating between bacterial sepsis and non-sepsis, with an AUC value of 0.85 and an average precision of 0.91 in the testing set. Based on the SHAP value, the top nine features of the model were PCT, CPM, CRP, ALB, SBPmin, RRmax, CREA, PLT and HRmax. ConclusionWe demonstrated the potential of machine-learning approaches for predicting bacterial sepsis based on optimized mcfDNA sequencing assay accurately.

Diagnostic Value of Microbial Cell-free DNA Sequencing for Suspected Invasive Fungal Infections: A Retrospective Multicenter Cohort Study.

An early diagnosis and treatment of invasive fungal disease (IFD) is associated with improved outcome, but the moderate sensitivity of noninvasive diagnostic tests makes this challenging. Invasive diagnostic procedures such as bronchoalveolar lavage (BAL) have a higher yield but are not without risk. The detection and sequencing of microbial cell-free DNA (mcfDNA) may facilitate a noninvasive diagnosis. In a prospective observational study, we collected plasma in the 120 hours preceding or following a BAL in patients with hematological malignancies suspected for a pulmonary IFD. The EORTC/MSGERC2020 criteria were used for IFD classification. Sequencing was performed by Karius (Redwood City, CA) using their Karius Test (KT) on plasma and a "research use only test" on BAL fluid if available. Cases with a probable/proven IFD were identified based on standard diagnostic tests on serum and BAL (microscopy, polymerase chain reaction, galactomannan, culture) and used to calculate the sensitivity, specificity, and additional diagnostic value of the KT. Of 106 patients enrolled, 39 (37%) had a proven/probable invasive aspergillosis, 7 (7%) a non-Aspergillus IFD, and 4 (4%) a mixed IFD. The KT detected fungal mcfDNA in 29 (28%) patients. Compared with usual diagnostic tests, the sensitivity and specificity were 44.0% (95% confidence interval [CI], 31.2-57.7) and 96.6% (95% CI, 88.5%-99.1%). Sensitivity of the KT was higher in non-Aspergillus IFD (Mucorales:2/3, Pneumocystis jirovecii: 3/5). On BAL, the sensitivity was 72.2% (95% CI, 62.1-96.3), and specificity 83.3% (95% CI, 49.1-87.5). Sequencing of mcfDNA may facilitate a noninvasive diagnosis of IFD in particular non-Aspergillus IFD. However, on plasma and similar to currently available diagnostics, it cannot be used as a "rule-out" test.

Plasma Microbial Cell-Free DNA Sequencing for Pathogen Detection and Quantification in Children With Musculoskeletal Infections.

Nearly half of all pediatric musculoskeletal infections (MSKIs) are culture negative. Plasma microbial cell-free DNA (mcfDNA) sequencing is noninvasive and not prone to the barriers of culture. We evaluated the performance of plasma mcfDNA sequencing in identifying a pathogen, and examined the duration of pathogen detection in children with MSKIs. We conducted a prospective study of children, aged 6 months to 18 years, hospitalized from July 2019 to May 2022 with MSKIs, in whom we obtained serial plasma mcfDNA sequencing samples and compared the results with cultures. A pathogen was recovered by culture in 23 of 34 (68%) participants, and by initial mcfDNA sequencing in 25 of 31 (81%) participants. Multiple pathogens were detected in the majority (56%) of positive initial samples. Complete concordance with culture (all organisms accounted for by both methods) was 32%, partial concordance (at least one of the same organism(s) identified by both methods) was 36%, and discordance was 32%. mcfDNA sequencing was more likely to show concordance (complete or partial) if obtained prior to a surgical procedure (82%), compared with after (20%), (RR 4.12 [95% CI 1.25, 22.93], p = .02). There was no difference in concordance based on timing of antibiotics (presample antibiotics 60% vs no antibiotics 75%, RR 0.8 [95% CI 0.40, 1.46], p = .65]). mcfDNA sequencing was positive in 67% of culture-negative infections and detected a pathogen for a longer interval than blood culture (median 2 days [IQR 1, 6 days] vs 1 day [1, 1 day], p < .01). Plasma mcfDNA sequencing may be useful in culture-negative pediatric MSKIs if the sample is obtained prior to surgery. However, results must be interpreted in the appropriate clinical context as multiple pathogens are frequently detected supporting the need for diagnostic stewardship.

Use of Advanced Diagnostics for Timely Identification of Travel-associated Leptospira santarosai Infection in Four Adolescents Through Plasma Microbial Cell-free DNA Sequencing With the Karius Test.

Leptospirosis is an important zoonotic infection worldwide. Diagnosis of leptospirosis is challenging given its nonspecific clinical symptoms that overlap with other acute febrile illnesses and limitations with conventional diagnostic testing. Alternative advanced diagnostics, such as microbial cell-free DNA (mcfDNA), are increasingly being used to aid in the diagnosis of infections and can be applied to pathogens with public health importance such as Leptospira , a nationally notifiable disease. The Karius Test uses plasma mcfDNA sequencing to detect and quantify DNA-based pathogens. This test offered through the Karius lab detected 4 cases of Leptospira santarosai during a 5-month period across the United States in 2021 and were clinically reviewed. In our case series, 4 adolescents with recent travel to Central America (Costa Rica, n = 3 and Belize, n = 1) from April to August 2021 were diagnosed with leptospirosis. While a large workup was performed in all cases, mcfDNA testing was the first test to detect L. santarosai as the microbiological diagnosis in all cases. Results of the Karius Test enabled rapid, noninvasive diagnosis of leptospirosis allowing for targeted therapy. Use of mcfDNA can be utilized for diagnosis of pathogens where conventional testing is challenging or limited. This in turn can enable quick diagnosis for targeted treatment and potentially aid in supporting case definitions of reportable diseases of public health concern.

Next-Generation Sequencing of Microbial Cell-Free DNA to Rapidly Detect Fluoribacter Bozemanae Pneumonia in an Immunocompromised Host

Background: Fluoribacter bozemanae is an uncommon pathogen that accounts for just 3-5% of cases of pneumonia caused by the different Legionella species. The mortality rate has been reported to be up to 40%. This organism is difficult to identify, making diagnosis extremely challenging with current diagnostic modalities. Case Report: We present a case of a 75-year-old female with a history of multiple myeloma undergoing active treatment with immunosuppressive agents who presented with confusion, hypoxemic respiratory failure and sepsis. Her initial presentation was consistent with Legionella infection, however, all routine testing including a Legionella urine antigen test came back negative. A CT scan of the chest was completed which showed near complete left lower lobe consolidation concerning for pneumonia. An infectious workup was initiated. Atypical and viral pneumonia polymerase chain reaction panel was negative. Microbial cell-free DNA sequencing returned positive for Fluoribacter bozemanae, a subspecies of the Legionellaceae family that is known to cause severe pneumonia in immunocompromised hosts. This information allowed a therapy adjustment resulting in rapid improvement of our patient’s symptoms. Conclusion: In cases such as this one, the diagnosis of Legionella species is often missed due to the many challenges associated with the different testing modalities. In these circumstances, next-generation genetic sequencing can be extremely useful. Now with the increasing availability of next-generation sequencing as a microbiological diagnostic tool, we can diagnose many more infections that once would have gone undiagnosed and either untreated or delayed in treatment.

872. Characterizing Plasma Microbial Cell-Free DNA Sequencing Detections of Public Health Important Pathogens

Abstract Background Timely pathogen identification is critical for meaningful disease surveillance to facilitate effective public health responses. However, public health important pathogens are often diagnostically challenging (e.g., indeterminate serological results, multiple samples separated by long intervals, lengthy turnaround times) and at odds with public health needs. We describe detections of public health important pathogens by the Karius Test®, a validated plasma microbial cell-free DNA (mcfDNA) sequencing test, providing real-time pathogen detection. Methods We identified nationally notifiable infectious diseases (NNID)-associated and selected state reportable pathogens detected and quantified as DNA molecules/μl (MPM) in US patients’ plasma samples submitted to the Karius CLIA certified/CAP accredited laboratory for mcfDNA sequencing between 4/1/18–4/30/22. We evaluated and characterized these detections based on result and test requisition form data. We reviewed gender and immunocompromised status of a subset of patients linked deterministically to the Premier Healthcare Database (PHD), a US hospital-based, all-payer database. Results Plasma mcfDNA sequencing yielded 520 detections of 62 microbes associated with 27 NNIDs and 449 detections of an additional 12 microbes, including public health important parasites, amoebae, endemic mycoses, and selected bacteria, across 27 US states. MPM and patient age varied widely across microbes from 9–300+ million and 0–89 years, respectively (Table 1). For the 167 (17%) PHD-linked detections, 71% were associated with male and 72% with immunocompromised patients. Conclusion Plasma mcfDNA sequencing detected many different public health important pathogens across many states, especially among immunocompromised patients. These patients pose a heightened public health concern given their increased risk for more severe disease and potential for longer infectious periods and greater likelihood of atypical or nonspecific presentations, leading to greater risk of unrecognized disease spread. Plasma mcfDNA sequencing, an unbiased test, may contribute to rapidly identifying disease outbreaks and spread, and facilitate timely interventions to improve public health. Disclosures Constance Lau, MPH, Karius, Inc.: Stocks/Bonds David Berman, DO, Precision Health Solutions, St. Petersburg, Florida: Advisor/Consultant Frederick S. Nolte, PhD, Karius: Stocks/Bonds

870. Plasma microbial cell-free DNA sequencing impacts antimicrobial management in immunocompromised patients with pneumonia

Abstract Background Microbial cell-free DNA (mcfDNA) sequencing can establish the etiology of multiple infectious syndromes by identifying pathogen DNA from the plasma of infected patients. Here, we describe the potential impact of a positive mcfDNA result on clinical decision making among immunocompromised adults with suspected pneumonia. Methods This prospective observational study evaluated the potential utility of mcfDNA sequencing in adults with active hematological malignancies undergoing a diagnostic bronchoscopy for pneumonia at 10 US Medical Centers as part of the PICKUP Study (Abstract # 544 IDWeek 2022). Plasma mcfDNA was collected on all participants at the time of bronchoscopy. Clinical impact of the mcfDNA sequencing results vs usual care (UC) testing – including bronchoscopy- were adjudicated and then compared for: 1) identification of probable cause of pneumonia or clinically significant non-pulmonary infection and 2) potential changes to antimicrobial therapy if mcfDNA sequencing results were available to treating clinicians. Results Of 223 participants analyzed, median (IQR) age was 62 (50-69) years and 72 (32.3%) were female. Plasma mcfDNA identified a probable cause of pneumonia in 57/223 (25.6%, 95% CI 20.0-31.8) participants and could have changed antimicrobial therapy in 21/57 (36.8%, 95% CI 24.4-50.7). A probable cause of pneumonia was identified by mcfDNA in 23/223 (10.3%, 95% CI 6.7-15.1) participants when no cause was identified by UC, and these detections could have resulted in an antimicrobial change in 17/23 (73.9%, 95% CI 51.6-89.8). A clinically relevant non-pulmonary infection was identified in 88/223 (39.5%, 95% CI 33.0-46.2) participants and antimicrobial therapy could have changed in 22/88 (25.0%, 95% CI 16.4-35.4). Collectively, antimicrobial therapy could have changed for 41/223 (18.4%, 95% CI 13.5-24.1) participants if mcfDNA results were available to treating clinicians. Conclusion Positive plasma mcfDNA sequencing results could have supported changes in clinical management for pneumonia and non-pulmonary infections among immunocompromised patients undergoing bronchoscopy. Further studies are needed to refine the optimal timing of mcfDNA in relation to UC testing and establish the impact of real-time mcfDNA results on patient outcomes. Disclosures Deng B. Madut, MD, Karius: Advisor/Consultant Roy F. Chemaly, MD/MPH, Eurofins-VViracor: Grant/Research Support|Karius: Advisor/Consultant Sanjeet S. Dadwal, MD, FACP, FIDSA, Allovir: Advisor/Consultant|Allovir: Grant/Research Support|Ansun Biopharma: Grant/Research Support|Aseptiscope, Inc: Stocks/Bonds|Astellas: Honoraria|Karius: Grant/Research Support|Matinas Biopharma: Stocks/Bonds|Merck: Advisor/Consultant|Merck: Grant/Research Support|Pfizer/Amplyx: Grant/Research Support|Takeda: Advisor/Consultant|Takeda: Honoraria|Viracor: Honoraria Joshua A. Hill, MD, Allovir: Advisor/Consultant|Allovir: Grant/Research Support|Century Therapeutics: Advisor/Consultant|Covance/CSL: Advisor/Consultant|Deverra: Grant/Research Support|Eversana Life Science Services, LLC: Advisor/Consultant|GeoVax: Grant/Research Support|Gilead: Advisor/Consultant|Gilead: Grant/Research Support|Karius: Advisor/Consultant|Karius: Grant/Research Support|Merck: Grant/Research Support|Moderna DSMB: Advisor/Consultant|Octapharma AG: Advisor/Consultant|OptumHealth: Advisor/Consultant|Oxford Immunotec: Grant/Research Support|Pfizer (previously Amplyx/Medpace): Advisor/Consultant|Senti BioSciences, Inc: Advisor/Consultant|Symbio: Advisor/Consultant|Takeda: Advisor/Consultant|Takeda: Grant/Research Support|Up-to-Date: Advisor/Consultant Yeon Joo Lee, MD, MPH, AiCuris: institutional research support for clinical trials|Karius: institutional research support for clinical trials|Merck: Grant/Research Support|Scynexis: institutional research support for clinical trials Ghady Haidar, MD, Allovir: Grant/Research Support|AstraZeneca: Advisor/Consultant|AstraZeneca: Grant/Research Support|Karius: Advisor/Consultant|Karius: Grant/Research Support|NIH: Grant/Research Support Alfred Luk, MD, Bill &amp; Melinda Gates Foundation: Grant/Research Support|Karius: Advisor/Consultant|Karius: Grant/Research Support Fareed Khawaja, MBBS, MEDSCAPE: Honoraria|Viracor: Grant/Research Support Genovefa Papanicolaou, MD, Allovir: Advisor/Consultant|Amplyx: Advisor/Consultant|Astellas: Advisor/Consultant|Cidara: Advisor/Consultant|CSL Behring: Advisor/Consultant|DSMC: Advisor/Consultant|Merck: Advisor/Consultant|Merck: Grant/Research Support|Merck: institutional research support for clinical trials|MSD: Advisor/Consultant|Octapharma: Advisor/Consultant|Partners Rx: Advisor/Consultant|Shire/Takeda: institutional research support for clinical trials|Symbio: Advisor/Consultant|Symbio: Advisor/Consultant|Takeda: Advisor/Consultant|Vera Pharma: Advisor/Consultant Micah T. McClain, MD, PhD, Biomeme Inc: Methods to diagnose and treat acute respiratory infections Eileen K. Maziarz, MD, Karius, Inc: Advisor/Consultant Robert Bigelow, PhD, Covidien: Stocks/Bonds|Elixir Medical: Advisor/Consultant|Johnson &amp; Johnson: Stocks/Bonds|Mckesson: Stocks/Bonds|Merck: Stocks/Bonds|Organon: Stocks/Bonds|Pfizer: Stocks/Bonds|Sanofi: Stocks/Bonds|Viatris: Stocks/Bonds Daniel Lupu, MD, PHD, Karius Inc: Employee|Karius Inc: Stocks/Bonds Sivan Bercovici, PhD, Karius: Stocks/Bonds Bradley A. Perkins, MD, Karius, Inc: Stocks/Bonds Timothy A. Blauwkamp, PhD, Karius: Board Member|Karius: Ownership Interest Vance G. Fowler, MD, MHS, Amphliphi Biosciences, Integrated Biotherapeutics; C3J, Armata, Valanbio; Akagera, Aridis, Roche, Astra Zeneca: Advisor/Consultant|Genentech, Regeneron, Deep Blue, Basilea, Janssen;: Grant/Research Support|Infectious Diseases Society of America: Honoraria|MedImmune, Allergan, Pfizer, Advanced Liquid Logics, Theravance, Novartis, Merck; Medical Biosurfaces; Locus; Affinergy; Contrafect; Karius;: Grant/Research Support|Novartis, Debiopharm, Genentech, Achaogen, Affinium, Medicines Co., MedImmune, Bayer, Basilea, Affinergy, Janssen, Contrafect, Regeneron, Destiny,: Advisor/Consultant|Sepsis diagnostic: Patent pending|UpToDate: Royalties|Valanbio and ArcBio: Stock Options Thomas L. Holland, MD, Aridis: Advisor/Consultant|Basilea Pharmaceutica: Advisor/Consultant|Karius: Advisor/Consultant|Lysovant: Advisor/Consultant Stephen P. Bergin, MD, Karius, Inc.: Grant/Research Support

4 Diagnostic utility of plasma microbial cell-free DNA sequencing in people with cystic fibrosis

4 Diagnostic utility of plasma microbial cell-free DNA sequencing in people with cystic fibrosis

Plasma Microbial Cell-Free DNA Sequencing from over 15,000 Patients Identified a Broad Spectrum of Pathogens.

Microbial cell-free DNA (mcfDNA) sequencing is an emerging infectious disease diagnostic tool which enables unbiased pathogen detection and quantification from plasma. The Karius Test, a commercial mcfDNA sequencing assay developed by and available since 2017 from Karius, Inc. (Redwood City, CA), detects and quantifies mcfDNA as molecules/μL in plasma. The commercial sample data and results for all tests conducted from April 2018 through mid-September 2021 were evaluated for laboratory quality metrics, reported pathogens, and data from test requisition forms. A total of 18,690 reports were generated from 15,165 patients in a hospital setting among 39 states and the District of Columbia. The median time from sample receipt to reported result was 26 h (interquartile range [IQR] 25 to 28), and 96% of samples had valid test results. Almost two-thirds (65%) of patients were adults, and 29% at the time of diagnostic testing had ICD-10 codes representing a diverse array of clinical scenarios. There were 10,752 (58%) reports that yielded at least one taxon for a total of 22,792 detections spanning 701 unique microbial taxa. The 50 most common taxa detected included 36 bacteria, 9 viruses, and 5 fungi. Opportunistic fungi (374 Aspergillus spp., 258 Pneumocystis jirovecii, 196 Mucorales, and 33 dematiaceous fungi) comprised 861 (4%) of all detections. Additional diagnostically challenging pathogens (247 zoonotic and vector-borne pathogens, 144 Mycobacterium spp., 80 Legionella spp., 78 systemic dimorphic fungi, 69 Nocardia spp., and 57 protozoan parasites) comprised 675 (3%) of all detections. This is the largest reported cohort of patients tested using plasma mcfDNA sequencing and represents the first report of a clinical grade metagenomic test performed at scale. Data reveal new insights into the breadth and complexity of potential pathogens identified.

Serial Quantitation of Plasma Microbial Cell-Free DNA Before and After Diagnosis of Pulmonary Invasive Mold Infections After Hematopoietic Cell Transplant.

Plasma microbial cell-free DNA sequencing (mcfDNA-Seq) is a noninvasive test for microbial diagnosis of invasive mold infection (IMI). The utility of mcfDNA-Seq for predicting IMI onset and the clinical implications of mcfDNA concentrations are unknown. We retrospectively tested plasma from hematopoietic cell transplant (HCT) recipients with pulmonary IMI and ≥1 mold identified by mcfDNA-Seq in plasma collected within 14 days of clinical diagnosis. Samples collected from up to 4 weeks before and 4 weeks after IMI diagnosis were evaluated using mcfDNA-Seq. Thirty-five HCT recipients with 39 IMIs (16 Aspergillus and 23 non-Aspergillus infections) were included. Pathogenic molds were detected in 38%, 26%, 11%, and 0% of samples collected during the first, second, third, and fourth week before clinical diagnosis, respectively. In non-Aspergillus infections, median mcfDNA concentrations in samples collected within 3 days of clinical diagnosis were higher in infections with versus without extrapulmonary spread (4.3 vs 3.3 log10 molecules per microliter [mpm], P = .02), and all patients (8/8) with mcfDNA concentrations >4.0 log10 mpm died within 42 days after clinical diagnosis. Plasma mcfDNA-Seq can identify pathogenic molds up to 3 weeks before clinical diagnosis of pulmonary IMI. Plasma mcfDNA concentrations may correlate with extrapulmonary spread and mortality in non-Aspergillus IMI.

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

Microbial cell free DNA sequencing is increasingly used for diagnosis of infection but few studies describe its utility in real-world settings. We performed a single-center retrospective case series of microbial cell free DNA testing using the Karius assay from 29 patient samples to define the clinical reasoning and the impact of testing. Indications fell into 3 categories, identifying a causative pathogen in patients with an infectious syndrome and negative microbiologic workup (15/29, 52%), seeking another pathogen when organisms identified by traditional diagnostics failed to explain the clinical presentation (9/29, 31%) and to "rule out" infection in patients with nonspecific symptoms and negative microbiologic workup (5/29, 17%). Clinical impact was positive in 13/29 (45%) and all were for patients with high pretest probability for infection. Impact was negative in 3/29 (10%) cases. There was no impact in 15/29 (52%) cases. Further work is needed to define the optimal timing accounting for test performance, and patient characteristics.

Cell-free plasma next-generation sequencing assists in the evaluation of secondary pneumonia in patients with COVID-19: a case series.

Secondary pneumonia occurs in 8-24% of patients with Coronavirus 2019 (COVID-19) infection and is associated with increased morbidity and mortality. Diagnosis of secondary pneumonia can be challenging. The purpose of this study was to evaluate the use of plasma microbial cell free DNA sequencing (mcfNGS) in the evaluation of secondary pneumonia after COVID-19. We performed a single-center case series of patients with COVID-19 who underwent mcfNGS to evaluate secondary pneumonia and reported the organisms identified, concordance with available tests, clinical utility, and outcomes. In 8/13 (61%) cases, mcfNGS detected 1-6 organisms, with clinically significant organisms identified in 4 cases, including Pneumocystis jirovecii, and Legionella spp. Management was changed in 85% (11/13) of patients based on results, including initiation of targeted therapy, de-escalation of empiric antimicrobials, and avoiding contingent escalation of antifungals. mcfNGS may be helpful to identify pathogens causing secondary pneumonia, including opportunistic pathogens in immunocompromised patients with COVID-19. However, providers need to carefully interpret this test within the clinical context.

Problems with etiologic diagnosis of community-acquired pneumonia using plasma microbial cell-free DNA sequencing.

Problems with etiologic diagnosis of community-acquired pneumonia using plasma microbial cell-free DNA sequencing.

Could cell-free DNA and host biomarkers assist in antimicrobial stewardship with organ transplant recipients?

Antimicrobial stewardship in solid organ transplant (SOT) recipients is important to prevent antimicrobial-associated complications, but traditional stewardship principles are challenging to implement for SOT patients. Newer methodologies to optimize stewardship efforts are needed. PubMed was searched using the keywords "cell free DNA," "metagenomic sequencing," "host biomarker," "antimicrobial stewardship," and "SOT." Metagenomic sequencing of cell free DNA has the potential to be a stewardship tool for SOT recipients. Various studies have shown its use for antimicrobial de-escalation and duration shortening. Host gene expression profiles can differentiate between infectious and noninfectious syndromes and may assist in stewardship efforts. However, information in immunocompromised hosts is conflicting. Microbial cell free DNA sequencing and host gene expression profiling show promise as stewardship tools in SOT recipients. Future studies on antimicrobial stewardship in SOT recipients should focus on their clinical use and feasibility.

#14 Rapid, Non-Invasive Detection of Non-H. pylori Helicobacter Infections in Immunocompromised Children Using Microbial Cell-Free DNA Next Generation Sequencing in Plasma

Abstract Background Non-H. pylori Helicobacter (NHPH) infections are more common in immunocompromised hosts and are associated with chronic infection in patients with X-linked agammaglobulinemia. Enterohepatic Helicobacter spp. cause systemic disease including cellulitis, bacteremia, endocarditis, meningitis, arthritis, hepatobiliary disease, and enteritis. NHPH are fastidious gram-negative organisms and are rarely detected by culture or nucleic acid amplification tests in clinical laboratories, resulting in potentially poor clinical detection and treatment. We present data demonstrating the diagnostic advantage of using plasma microbial cell-free DNA Sequencing to rapidly identify NHPH to the species level. Method The Karius TestTM (KT) was developed and validated in Karius’s CLIA certified/CAP accredited lab (Redwood City, CA) and detects mcfDNA in plasma. Following DNA extraction, next-generation sequencing (NGS) is performed, and sequences are aligned to a curated database of &amp;gt; 1000 organisms. Microorganisms observed above background at statistically significant levels are reported and quantified in molecules per microliter (MPM). We conducted a retrospective review of KT detections of NHPH from December 2016-November 2021. A subset of pediatric patients (age &amp;lt;=21 years) was identified from this cohort. Available clinical information was extracted from the test requisition form. Results KT detected NHPH in 23 patients among 11 unique institutions in the span of 5 years, including 10 (43%) pediatric patients (Table 1). Nine of ten detections were quantified (Median 110 MPM; range 48-20932, MPM). The reference interval of mcfDNA abundance for all NHPH species (defined by the 97.5th %ile) in a cohort of 684 healthy subjects is 0 MPM (for comparison the reference interval for H. pylori is 42.2 MPM). The highest detection was H. magdeburgensis 20,932 MPM. Of the 10 patients, 8 were male and 2 were female and the mean age was 10.5 years (range 3-17). Nine of 10 patients had information regarding underlying diagnosis. There were 6 patients with primary immunodeficiency including 5 with X-linked agammaglobulinemia with a diverse manifestation of infections. Two patients had serial testing during the intercurrent infectious episode to monitor the response to treatment. Serial testing in one patient showed a dramatic decrease of NHPH mcfDNA from 27,907 MPM to 1,079 MPM over a 6-day span. Serial testing in a second patient showed a decrease of the NHPH mcfDNA from 124 MPM to an undetectable range 14 days later. Conclusion These cases highlight the potential use of rapid, non-invasive, plasma mcfDNA to diagnose and potentially monitor the response to treatment of infections caused by NHPH, especially in patients with primary immunodeficiency. NHPH are difficult to detect and identify using conventional microbiological methods and plasma mcfDNA NGS may play an important role in detecting these fastidious microorganisms and serial testing.