Simultaneous detection of influenza A, B and respiratory syncytial virus in wastewater samples by one-step multiplex RT-ddPCR assay.

BACKGROUND: After the occurrence of the COVID-19 pandemic, detection of other disseminated respiratory viruses using highly sensitive molecular methods was declared essential for monitoring the spread of health-threatening viruses in communities. The development of multiplex molecular assays are essential for the simultaneous detection of such viruses even at low concentrations. In the present study, a highly sensitive and specific multiplex one-step droplet digital PCR (RT-ddPCR) assay was developed for the simultaneous detection and absolute quantification of influenza A (IAV), influenza B (IBV), respiratory syncytial virus (RSV), and beta-2-microglobulin transcript as an endogenous internal control (IC B2M). RESULTS: The assay was first evaluated for analytical sensitivity and specificity, linearity, reproducibility, and recovery rates with excellent performance characteristics and then applied to 37 wastewater samples previously evaluated with commercially available and in-house quantitative real-time reverse transcription PCR (RT-qPCR) assays. IAV was detected in 16/37 (43%), IBV in 19/37 (51%), and RSV in 10/37 (27%) of the wastewater samples. Direct comparison of the developed assay with real-time RT-qPCR assays showed statistically significant high agreement in the detection of IAV (kappa Cohen's correlation coefficient: 0.834, p = 0.001) and RSV (kappa: 0.773, p = 0.001) viruses between the two assays, while the results for the detection of IBV (kappa: 0.355, p = 0.27) showed good agreement without statistical significance. CONCLUSIONS: Overall, the developed one-step multiplex ddPCR assay is cost-effective, highly sensitive and specific, and can simultaneously detect three common respiratory viruses in the complex matrix of wastewater samples even at low concentrations. Due to its high sensitivity and resistance to PCR inhibitors, the developed assay could be further used as an early warning system for wastewater monitoring.

Enhancing Sensitivity in Detecting Severe Fever With Thrombocytopenia Syndrome Virus: Development of a Reverse Transcription-Droplet Digital Polymerase Chain Reaction.

Severe fever with thrombocytopenia syndrome (SFTS) is a highly fatal disease. Droplet digital polymerase chain reaction (ddPCR) presents unparalleled sensitivity and enables absolute quantification of viral load. In this prospective study, we enrolled 111 patients with SFTS and collected 259 continuous samples. Our findings unveil a robust reverse transcription (RT)-ddPCR method for SFTS with a limit of detection of 2.46 copies/µL (95% CI, 1.50-11.05), surpassing the sensitivity of RT-quantitative polymerase chain reaction at 103.29 copies/µL (95% CI, 79.69-216.35). Longitudinal cohort analysis revealed significantly higher RT-ddPCR detection rates at days 10 to 11, 13 to 14, and ≥15 of the disease course as compared with RT-quantitative polymerase chain reaction (P < .05). Positive RT-ddPCR results were associated with declined platelet and elevated aspartate aminotransferase and lactate dehydrogenase on the same day vs negative RT-ddPCR samples. RT-ddPCR exhibits commendable diagnostic efficacy in SFTS, and it remains detectable in blood samples from patients with an extended disease course. Furthermore, RT-ddPCR correlates with clinical laboratory tests, furnishing valuable reference data for clinical diagnosis.

Hepatitis B virus DNA and RNA persist in liver after serologic recovery in persons with hepatitis C virus.

After recovery from a hepatitis B virus (HBV) infection, reactivation can occur with immunosuppression; thus, it is assumed that replication competent HBV persists in the liver. We sought to detect persistent HBV from 13 people with spontaneous recovery. We quantified HBV DNA and RNA in core liver biopsies (median 1.72x106 cells) from people who inject drugs (PWID). Among 13 biopsies, 8 (61%) had evidence of HBV DNA or RNA and 5 (38%) had both HBV DNA and RNA. mRNAs derived from cccDNA and integrated HBV DNA. Here, we show prevalent HBV DNA and RNA despite clinical recovery in PWID.

We used a sensitive method to determine the amount of hepatitis B virus DNA or RNA in the livers of 13 individuals who recovered from hepatitis B virus infection. We found viral DNA or RNA in the liver in 61% of individuals despite no detectable virus in blood. Our findings support that eliminating all hepatitis B from the liver is a difficult treatment goal.

Analysis of the relative frequencies of the multipartite BNYVV genomic RNAs in different plants and tissues.

Multipartite virus genomes are composed of two or more segments, each packaged into an independent viral particle. A potential advantage of multipartitism is the regulation of gene expression through changes in the segment copy number. Soil-borne beet necrotic yellow vein virus (BNYVV) is a typical example of multipartism, given its high number of genomic positive-sense RNAs (up to five). Here we analyse the relative frequencies of the four genomic RNAs of BNYVV type B during infection of different host plants (Chenopodium quinoa, Beta macrocarpa and Spinacia oleracea) and organs (leaves and roots). By successfully validating a two-step reverse-transcriptase digital droplet PCR protocol, we show that RNA1 and -2 genomic segments always replicate at low and comparable relative frequencies. In contrast, RNA3 and -4 accumulate with variable relative frequencies, resulting in distinct RNA1 : RNA2 : RNA3 : RNA4 ratios, depending on the infected host species and organ.

Evaluation of reverse transcription yield of RNA standards and forensic samples based on droplet digital PCR.

RNA analysis has shown great value in forensic science, such as body fluids and tissue identification, postmortem interval estimation, biological age prediction, etc. Currently, most RNA follow-up experiments involve reverse transcription (RT) procedures. It has been shown that the RT step is variable and has a greater impact on subsequent data analysis, especially for forensic trace samples. However, the pattern of variation between different RNA template inputs and complementary DNA (cDNA) yield is unclear. In this study, a series of 2-fold gradient dilutions of RNA standards (1 µg/µL - 0.24 ng/µL) and forensic samples (including blood samples, saliva samples, bloodstains, and saliva stains) were reverse-transcribed using EasyQuick RT MasterMix. The obtained cDNA was quantified by droplet digital PCR (ddPCR) to assess the RT yield of the ACTB gene. The results showed that the 125 ng RNA template had the highest RT yield in a 10 µL RT reaction system with the selected kit. For all stain samples, the RT yield improved as the amount of RNA template input increased since RNA quantities were below 125 ng. As many commercialized reverse transcription kits using different kinds of enzymes are available for forensic RNA research, we recommend that systematic experiments should be performed in advance to determine the amount of RNA input at the optimum RT yield when using any kit for reverse transcription experiments.

Increased circulation of human adenovirus in 2023: an investigation of the circulating genotypes, upper respiratory viral loads, and hospital admissions in a large academic medical center.

IMPORTANCE: The circulation of human adenoviruses (HAdV) increased in 2023. In this manuscript, we show that HAdV-B3 was predominant in 2023 in a cohort characterized by the Johns Hopkins Hospital System. We also show that HAdV-B3 was associated with an increase in viral loads in respiratory samples and provide a correlation with the clinical presentations and outcomes.

Measurable residual disease monitoring by ddPCR in the early posttransplant period complements the traditional MFC method to predict relapse after HSCT in AML/MDS: a multicenter retrospective study.

BACKGROUND: Droplet digital PCR (ddPCR) is widely applied to monitor measurable residual disease (MRD). However, there are limited studies on the feasibility of ddPCR-MRD monitoring after allogeneic hematopoietic stem cell transplantation (allo-HSCT), especially targeting multiple molecular markers simultaneously. METHODS: Our study collected samples from patients with acute myeloid leukemia (AML) or high-risk myelodysplastic syndrome (MDS) in complete remission after allo-HSCT between January 2018 and August 2021 to evaluate whether posttransplant ddPCR-MRD monitoring can identify patients at high risk of relapse. RESULTS: Of 152 patients, 58 (38.2%) were MRD positive by ddPCR within 4 months posttransplant, with a median variant allele frequency of 0.198%. The detectable DTA mutations (DNMT3A, TET2, and ASXL1 mutations) after allo-HSCT were not associated with an increased risk of relapse. After excluding DTA mutations, patients with ddPCR-MRD positivity had a significantly higher cumulative incidence of relapse (CIR, 38.7% vs. 9.7%, P < 0.001) and lower rates of relapse-free survival (RFS, 55.5% vs. 83.7%, P < 0.001) and overall survival (OS, 60.5% vs. 90.5%, P < 0.001). In multivariate analysis, ddPCR-MRD positivity of non-DTA genes was an independent adverse predictor for CIR (hazard ratio [HR], 4.02; P < 0.001), RFS (HR, 2.92; P = 0.002) and OS (HR, 3.12; P = 0.007). Moreover, the combination of ddPCR with multiparameter flow cytometry (MFC) can further accurately identify patients at high risk of relapse (F+/M+, HR, 22.44; P < 0.001, F+/M-, HR, 12.46; P < 0.001 and F-/M+, HR, 4.51; P = 0.003). CONCLUSION: ddPCR-MRD is a feasible approach to predict relapse after allo-HSCT in AML/MDS patients with non-DTA genes and is more accurate when combined with MFC. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT06000306. Registered 17 August 2023 -Retrospectively registered ( https://clinicaltrials.gov/study/NCT06000306?term=NCT06000306&rank=1 ).

Combining germline, tissue and liquid biopsy analysis by comprehensive genomic profiling to improve the yield of actionable variants in a real-world cancer cohort.

BACKGROUND: Comprehensive next-generation sequencing is widely used for precision oncology and precision prevention approaches. We aimed to determine the yield of actionable gene variants, the capacity to uncover hereditary predisposition and liquid biopsy appropriateness instead of, or in addition to, tumor tissue analysis, in a real-world cohort of cancer patients, who may benefit the most from comprehensive genomic profiling. METHODS: Seventy-eight matched germline/tumor tissue/liquid biopsy DNA and RNA samples were profiled using the Hereditary Cancer Panel (germline) and the TruSight Oncology 500 panel (tumor tissue/cfDNA) from 23 patients consecutively enrolled at our center according to at least one of the following criteria: no available therapeutic options; long responding patients potentially fit for other therapies; rare tumor; suspected hereditary cancer; primary cancer with high metastatic potential; tumor of unknown primary origin. Variants were annotated for OncoKB and AMP/ASCO/CAP classification. RESULTS: The overall yield of actionable somatic and germline variants was 57% (13/23 patients), and 43.5%, excluding variants previously identified by somatic or germline routine testing. The accuracy of tumor/cfDNA germline-focused analysis was demonstrated by overlapping results of germline testing. Five germline variants in BRCA1, VHL, CHEK1, ATM genes would have been missed without extended genomic profiling. A previously undetected BRAF p.V600E mutation was emblematic of the clinical utility of this approach in a patient with a liver undifferentiated embryonal sarcoma responsive to BRAF/MEK inhibition. CONCLUSIONS: Our study confirms the clinical relevance of performing extended parallel tumor DNA and cfDNA testing to broaden therapeutic options, to longitudinally monitor cfDNA during patient treatment, and to uncover possible hereditary predisposition following tumor sequencing in patient care.

Multiple factors trigger the formation and resuscitation of the VBNC state in alcohol-producing Klebsiella pneumoniae.

Klebsiella pneumoniae can enter a viable but nonculturable (VBNC) state to survive in unfavorable environments. Our research found that high-, medium-, and low-alcohol-producing K. pneumoniae strains are associated with nonalcoholic fatty liver disease. However, the presence of the three Kpn strains has not been reported in the VBNC state or during resuscitation. In this study, the effects of different strains, salt concentrations, oxygen concentrations, temperatures, and nutrients in K. pneumoniae VBNC state were evaluated. The results showed that high-alcohol-producing K. pneumoniae induced a slower VBNC state than medium-alcohol-producing K. pneumoniae, and low-alcohol-producing K. pneumoniae. A high-salt concentration and micro-oxygen environment accelerated the loss of culturability. Simultaneously, both real-time quantitative PCR and droplet digital PCR were developed to compare the quantitative comparison of three Kpn strain VBNC states by counting single-copy gene numbers. At 22°C or 37°C, the number of culturable cells decreased significantly from about 108 to 105-106 CFU/mL. In addition, imipenem, ciprofloxacin, polymyxin, and phiW14 inhibited cell resuscitation but could not kill VBNC-state cells. These results revealed that the different environments evaluated play different roles in the VBNC induction process, and new effective strategies for eliminating VBNC-state cells need to be further studied. These findings provide a better understanding of VBNC-state occurrence, maintenance, detection, and absolute quantification, as well as metabolic studies of resuscitation resistance and ethanol production.IMPORTANCEBacteria may enter VBNC state under different harsh environments. Pathogenic VBNC bacteria cells in clinical and environmental samples pose a potential threat to public health because cells cannot be found by routine culture. The alcohol-producing Kpn VBNC state was not reported, and the influencing factors were unknown. The formation and recovery of VBNC state is a complete bacterial escape process. We evaluated the influence of multiple induction conditions on the formation of VBNC state and recovery from antibiotic and bacteriophage inhibition, and established a sensitive molecular method to enumerate the VBNC cells single-copy gene. The method can improve the sensitivity of pathogen detection in clinical, food, and environmental contamination monitoring, and outbreak warning. The study of the formation and recovery of VBNC-state cells under different stress environments will also promote the microbiological research on the development, adaptation, and resuscitation in VBNC-state ecology.

An update of clinical value of circulating tumor DNA in esophageal cancer: a systematic review and meta-analysis.

BACKGROUND: Esophageal cancer (EC) is a deadly disease with limited therapeutic options. Although circulating tumor DNA (ctDNA) could be a promising tool in this regard, the availiable evidence is limited. We performed a systematic review and meta-analysis to summarize the clinical applicability of the next-generation sequencing (NGS) and droplet digital polymerase chain reaction (ddPCR) technology on the ctDNA detection of the EC and listed the current challenges. METHODS: We systematically searched MEDLINE (via PubMed), Embase (via OVID), ISI Web of Science database and Cochrane Library from January, 2000 to April, 2023. Progression-free survival (PFS) and overall survival (OS) were set as primary outcome endpoints. Pathologic response was evaluated by tumor regression grade (TRG), according to the eighth edition of the American Joint Committee on Cancer (AJCC). Major pathologic regression (MPR) was defined as TRG 1 and 2. The MPR was set as secondary endpoint. Hazard rate (HR) and associated 95% CI were used as the effect indicators the association between ctDNA and prognosis of EC. MPR rates were also calculated. Fixed-effect model (Inverse Variance) or random-effect model (Mantel-Haenszel method) was performed depending on the statistically heterogeneity. RESULTS: Twenty-two studies, containing 1144 patients with EC, were included in this meta-analysis. The results showed that OS (HR = 3.87; 95% CI, 2.86-5.23) and PFS (HR = 4.28; 95% CI, 3.34-5.48) were shorter in ctDNA-positive patients. In the neoadjuvant therapy, the sensitivity analysis showed the clarified HR of ctDNA-positive was 1.13(95% CI, 1.01-1.28). We also found that TP53, NOTCH1, CCND1 and CNKN2A are the most frequent mutation genes. CONCLUSIONS: Positive ctDNA is associated with poor prognosis, which demonstrated clinical value of ctDNA. Longitudinal ctDNA monitoring showed potential prognostic value in the neoadjuvant therapy. In an era of precision medicine, ctDNA could be a promising tool to individualize treatment planning and to improve outcomes in EC. PROSPERO REGISTRATION NUMBER: CRD42023412465.

Influence of dexamethasone-induced matrices on the TM transcriptome.

Pathologic bidirectional interactions between the extracellular matrix (ECM) and cells within the human trabecular meshwork (hTM) contribute to ocular hypertension. An in vitro model is needed to study these cell-matrix interactions and their effect on outflow homeostasis. This study aimed to determine whether pathogenic ECM derived from dexamethasone (DEX)-treated hTM cultures induces clinically relevant glaucoma-like changes in healthy hTM cells at the transcriptional level. Corneoscleral rims from non-glaucoma donors were used to isolate primary hTM cells after validation according to the consensus recommendations for TM culture. Normal hTM cells (n = 5) were plated on a coverslip and treated with 100 nM DEX or ethanol for four weeks. These cultures were then decellularized, plated with primary hTM cells, and allowed to grow for another 72 h. RNA was extracted from these hTM cells for stranded total RNA-Seq. Sequencing libraries prepared using the Zymo-Seq RiboFree Total RNA library kit were pooled and sequenced using Illumina NovaSeq 6000. After quality control, sequence reads were aligned to the human genome build hg19. Differential expression (DE) analyses were performed using paired multi-factorial ANOVA. The expression of several DE genes associated with glaucoma (ANGPTL2, PDE7B, C22orf23, COL4A1, ADAM12, IFT122, SEMA6C) was validated using EvaGreen-based Droplet Digital PCR (ddPCR) assays. Gene ontology analyses of the DE genes were performed using the PANTHER and NDEx IQA databases, and functional analyses were performed with the DAVID Bioinformatics software. Using a cutoff of p-value <0.05 and fold change ≥2.0, our differential analysis identified 267 up- and 135 down-regulated genes in DEX-induced ECM-treated cells compared to the control. These differentially expressed genes were found to play a significant role in pathways such as cytokine and oxidative stress-induced inflammation, integrin signaling, matrix remodeling, and angiogenesis. These findings were further supported by previously performed proteomics studies using the same model. Using ddPCR, we validated the expression of seven genes associated with the risk of primary open-angle glaucoma. These results not only provide support for the pathogenic ECM model of steroid-induced glaucoma, but also demonstrate that the pathologic changes induced by this model are indeed found at the transcriptional level. These findings further demonstrate that matrix changes significantly influence cell expression profiles, which enable further understanding of the molecular mechanisms underlying glaucomatous changes in the TM. However, future studies with a larger and more diverse set of samples and longer time points are needed to confirm the utility of this model for mechanistic studies.

Can novel methods replace the gold standard chimerism method after allogeneic hematopoietic stem cell transplantation?

After hematopoietic stem cell transplantation, chimerism assay is a useful approach to monitor the success of the transplant and to select the appropriate treatment strategy, such as donor leukocyte infusion or immunosuppressive drug dosage. Short tandem repeat PCR is the method that has been accepted as the gold standard for chimerism. However, it has not yet been sufficient to detect mixed chimerism in patients with minimal residual disease. Simultaneously, recent years have been marked by developing sensitive, high-throughput, and accurate molecular genetic assays. These novel methods have subsequently been adapted for the analysis of post-transplant chimerism. In this review, we discuss the technical features of both novel and conventional gold standard chimerism assays. We also discuss their advantages and disadvantages.

Origin of pathogenic variant and mosaicism in families with a sporadic case of haemophilia B.

INTRODUCTION: Of newly diagnosed cases of haemophilia B, the proportion of sporadic cases is usually 50% of severe cases and 25% of moderate/mild cases. However, cases presumed to be sporadic due to family history may not always be sporadic. Few case reports have been published on mosaicism in haemophilia B. AIM: The present study aimed to trace the origin of the pathogenic variant in a well-defined cohort of sporadic cases of haemophilia B by haplotyping markers. It also aimed to determine the frequency of mosaicism in presumed non-carrier mothers. METHODS: The study group was 40 families, each with a sporadic case of haemophilia B analysed in two-to-three generations by Sanger sequencing, haplotyping and using the sensitive droplet digital polymerase chain reaction (ddPCR) technique. RESULTS: In 31/40 (78%) of the families, the mother carried the same pathogenic variant as her son, while Sanger sequencing showed that 9/40 (22%) of the mothers did not carry this variant. Of these variants, 2/9 (22%) were shown to be mosaics by using the ddPCR technique. 16/21 carrier mothers, with samples from three generations available, had a de novo pathogenic variant of which 14 derived from the healthy maternal grandfather. CONCLUSION: The origin of the pathogenic variant in sporadic cases of haemophilia B is most often found in the X-chromosome derived from the maternal grandfather or, less often, from the maternal grandmother. Mosaic females seem to be found at the same frequency as in haemophilia A but at a lower percentage of the pathogenic variant.

Noninvasive minimal residual disease assessment in relapsed/refractory large B-cell lymphoma using digital droplet PCR.

Although several promising approaches for the treatment of relapsed/refractory diffuse large B-cell lymphoma (rrDLBCL) have been approved recently, it remains unclear which patients will ultimately achieve long-term responses. Circulating tumor (ct)DNA sequencing has emerged as a valuable tool to assess minimal residual disease (MRD). Correlations between MRD and outcomes have been shown in previously untreated DLBCL, but data on the repeated assessment of MRD in the dynamic course of rrDLBCL is limited. Here, we present an approach leveraging cost- and time-sensitivity of digital droplet (dd)PCR to repeatedly assess MRD in rrDLBCL and present proof-of-principle for its ability to predict outcomes.

Droplet digital PCR for sensitive relapse detection in acute myeloid leukaemia patients transplanted by reduced intensity conditioning.

INTRODUCTION: Follow-up after allogeneic transplantation in acute myeloid leukaemia (AML) is guided by measurable residual disease (MRD) testing. Quantitative polymerase chain reaction (qPCR) is the preferred MRD platform but unfortunately, 40%-60% of AML patients have no high-quality qPCR target. This study aimed to improve MRD testing by utilising droplet digital PCR (ddPCR). ddPCR offers patient-specific monitoring but concerns of tracking clonal haematopoiesis rather than malignant cells prompt further validation. METHODS: Retrospectively, we performed MRD testing on blood and bone marrow samples from AML patients transplanted by reduced-intensity conditioning. RESULTS: The applicability of ddPCR was 39/42 (92.9%). Forty-five ddPCR assays were validated with a 0.0089% median sensitivity. qPCR targeting NPM1 mutation detected relapse 46 days before ddPCR (p = .03). ddPCR detected relapse 34.5 days before qPCR targeting WT1 overexpression (p = .03). In non-relapsing patients, zero false positive ddPCR MRD relapses were observed even when monitoring targets associated with clonal haematopoiesis such as DNMT3A, TET2, and ASXL1 mutations. CONCLUSION: These results confirm that qPCR targeting NPM1 mutations or fusion transcripts are superior in MRD testing. In the absence of such targets, ddPCR is a promising alternative demonstrating (a) high applicability, (b) high sensitivity, and (c) zero false positive MRD relapses in non-relapsing patients.

High-efficiency EGFR genotyping using cell-free DNA in bronchial washing fluid.

BACKGROUND: EGFR mutation testing is required for treatment of lung adenocarcinoma using epidermal growth factor receptor-tyrosine kinase inhibitor. However, the amounts of tumor tissue or tumor cells obtained by bronchoscopy are often insufficient. Bronchial washing fluid, obtained by lavage with saline after tumor biopsy or brushing, and the supernatant of bronchial washing fluid are thought to contain cell-free DNA that would be potentially applicable for EGFR testing. METHODS: From among patients with suspected adenocarcinoma or non-small cell lung carcinoma diagnosed from biopsy or surgical specimens at the University of Tsukuba Hospital between 2015 and 2019, cell-free DNAs from 80 specimens of supernatant of bronchial washing fluid (50 with EGFR mutation and 30 with wild type EGFR) and 8 blood serum samples were examined for EGFR mutation using droplet digital PCR. RESULTS: Among the 50 patients harboring EGFR mutation, the rate of positivity for cell-free DNA extracted from supernatant of bronchial washing fluid was 80% (40/50). In nine of the EGFR mutation-positive cases, tumor cells were not detected by either biopsy or cytology, but the mutation was detected in four cases (4/9, 44%). Comparison of the cell-free DNA mutation detection rate between supernatant of bronchial washing fluid and blood serum in six cases showed that mutations were detected from the former in all cases (6/6, 100%), but from the latter in only one case (1/6, 17%). CONCLUSIONS: Using supernatant of bronchial washing fluid samples, the detection rate of EGFR mutation was high, and EGFR mutations were detectable even when no tumor cells had been detectable by biopsy or cytology. Supernatant of bronchial washing fluid might be an effective sample source for EGFR mutation testing.

Development of a multiplex droplet digital PCR method for detection and monitoring of Mycobacterium tuberculosis and drug-resistant tuberculosis.

BACKGROUND: The prevalence of multidrug-resistant tuberculosis (MDR-TB) among Korean tuberculosis patients is about 4.1%, which is higher than the OECD average of 2.6%. Inadequate drug use and poor patient compliance increase MDR-TB prevalence through selective pressure. Therefore, prompt detection of drug resistance in tuberculosis patients at the time of diagnosis and quantitative monitoring of these resistant strains during treatment are crucial. METHODS: A multiplex droplet digital PCR (ddPCR) assay was developed and assessed using DNA material of nine Mycobacterium tuberculosis strains with known mutation status that were purchased from the Korean National Tuberculosis Association. We collected a total of 18 MDR-TB residual samples referred for PCR analysis. Total DNA was extracted from the samples and subjected to the quadruplex ddPCR assay. Their results were compared to those of known resistance phenotypes. RESULTS: The analytical sensitivity and specificity of the multiplex ddPCR assay for detecting INH, RIF, EMB, FQ, and SM resistance-causing mutations ranged from 71.43 to 100% and 94.12-100%, respectively. Follow-up sample results showed that the quadruplex ddPCR assay was sensitive enough to detect IS6110 and other mutations even after onset of treatment. CONCLUSIONS: We developed a sensitive and accurate multiplex ddPCR assay that can detect the presence of tuberculosis quantitatively and resistance-conveying mutations concurrently. This tool could aid clinicians in the diagnosis and treatment monitoring of tuberculosis.

Inter-laboratory comparison of eleven quantitative or digital PCR assays for detection of proviral bovine leukemia virus in blood samples.

Bovine leukemia virus (BLV) is the etiological agent of enzootic bovine leukosis and causes a persistent infection that can leave cattle with no symptoms. Many countries have been able to successfully eradicate BLV through improved detection and management methods. However, with the increasing novel molecular detection methods there have been few efforts to standardize these results at global scale. This study aimed to determine the interlaboratory accuracy and agreement of 11 molecular tests in detecting BLV. Each qPCR/ddPCR method varied by target gene, primer design, DNA input and chemistries. DNA samples were extracted from blood of BLV-seropositive cattle and lyophilized to grant a better preservation during shipping to all participants around the globe. Twenty nine out of 44 samples were correctly identified by the 11 labs and all methods exhibited a diagnostic sensitivity between 74 and 100%. Agreement amongst different assays was linked to BLV copy numbers present in samples and the characteristics of each assay (i.e., BLV target sequence). Finally, the mean correlation value for all assays was within the range of strong correlation. This study highlights the importance of continuous need for standardization and harmonization amongst assays and the different participants. The results underscore the need of an international calibrator to estimate the efficiency (standard curve) of the different assays and improve quantitation accuracy. Additionally, this will inform future participants about the variability associated with emerging chemistries, methods, and technologies used to study BLV. Altogether, by improving tests performance worldwide it will positively aid in the eradication efforts.

SARS-CoV-2 wastewater surveillance at two university campuses: lessons learned and insights on intervention strategies for public health guidance.

Wastewater surveillance has been a tool for public health officials throughout the COVID-19 pandemic. Universities established pandemic response committees to facilitate safe learning for students, faculty, and staff. These committees met to analyze both wastewater and clinical data to propose mitigation strategies to limit the spread of COVID-19. This paper reviews the initial efforts of utilizing campus data inclusive of wastewater surveillance for SARS-CoV-2 RNA concentrations, clinical case data from university response teams, and mitigation strategies from Grand Valley State University in West Michigan (population 21,648 students) and Oakland University in East Michigan (population 18,552 students) from November 2020 to April 2022. Wastewater positivity rates for both universities ranged from 32.8 to 46.8%. Peak viral signals for both universities directly corresponded to variant points of entry within the campus populations from 2021 to 2022. It was found that the organization of clinical case data and variability of wastewater testing data were large barriers for both universities to effectively understand disease dynamics within the university population. We review the initial efforts of onboarding wastewater surveillance and provide direction for structuring ongoing surveillance workflows and future epidemic response strategies based on those that led to reduced viral signals in campus wastewater.

Molecular quantification of parasitic sea louse larvae depends on species and life stage.

Sea lice cause substantial economic and environmental harm to Norway's aquaculture industry and wild salmonid populations. Rapid, accurate quantification of lice larval densities in coastal waters remains the greatest bottleneck for providing empirical data on infestation risk within wild salmon habitats and aquaculture production regions. We evaluated the capability of droplet digital PCR (ddPCR) as an absolute quantification method for the planktonic stages of two parasitic louse species, Lepeophtheirus salmonis (Krøyer) and Caligus elongatus (von Nordman). Results demonstrated linear relationships between the DNA quantity measured and the number of spiked larvae for both species and life stages. However, L. salmonis contained a significantly greater number of DNA copies than C. elongatus individuals and for C. elongatus, nauplii displayed a significantly higher number of DNA copies than copepodids. Our results suggest that ddPCR can effectively enumerate louse larvae, but interpreting ddPCR results differ between the two louse species. Obtaining larval abundance estimates from marine plankton samples will depend on the nauplii to copepodid ratio for C. elongatus, but not for L. salmonis.