Journal of Virological Methods

African swine fever virus (ASFV), the etiologic agent of African Swine Fever (ASF), is a high-consequence pathogen requiring experiments to be conducted in containment in non-endemic countries, thereby restricting diagnostic development, the creation of reference standards, and proficiency testing (PT). Safe and reliable inactivation methods are essential to expand diagnostic capacity while preserving nucleic acid integrity for molecular assays in unaffected countries. This study employed gamma irradiation to achieve complete inactivation of ASFV without compromising downstream molecular detection, as gamma irradiation offers deep penetration and uniform dose delivery. ASFV-cell culture supernatants were subjected to gamma irradiation doses ranging from 2 to 50 kGy. Viral replication was evaluated using TCID{square}{square} and serial passages, revealing a consistent dose{square}dependent reduction in infectivity across increasing irradiation dose levels and a complete loss of ASFV infectivity at 30 and 50 kGy. Molecular detection remained unaffected at all of the tested doses as confirmed by qPCR Ct values and sequence identity of the p72 gene. Whole genome sequencing demonstrated >99% genome coverage and consistent read depth profiles across irradiated and non-irradiated samples, indicating preservation of genomic integrity at all tested doses. These findings demonstrate that gamma irradiation at 50 kGy fully inactivates ASFV-cell supernatants while maintaining nucleic acid quality suitable for molecular diagnostics. The resulting inactivated material meets quality assurance requirements for molecular reference standards and PT panels and can be safely distributed to laboratories outside high containment facilities, supporting broader diagnostic readiness and harmonization of ASFV testing.

Citrus yellow vein clearing virus (CYVCV) is the causal agent of an emerging disease representing a potentially high-impact threat for citrus production. Despite remaining outside Europe for decades, CYVCV has now expanded towards two important European citrus producers, Italy and, more recently, Spain. The presence of this virus in the EPPO region represents a current threat with unpredictable and potentially devastating consequences for European citriculture. Therefore, urgent protective measures need to be taken to prevent CYVCV spread and minimize its impact. Diagnostics is a key measure in the management of viral diseases, highlighting the need for harmonized methods suitable for reliable routine detection of the currently known CYVCV diversity. In this study, an inclusive, efficient and highly sensitive real-time RT-qPCR for the detection of CYVCV in plant material and transmission vectors has been developed and validated according to EPPO standards. Moreover, the validated method has been successfully adapted to both PCR digital platforms, that allow high-sensitive absolute quantitative detection, essential in the diagnostics at low viral concentrations; and PCR portable tools, that can be applied in a real diagnostic context for on-site detection. This versatility combines standard validated performance, absolute sensitive quantitation and real on-site detection. The study has also addressed sampling strategies to support reliable molecular diagnostic performance. Our results represent an improvement in the detection of CYVCV to be applied in epidemiological studies and different real diagnostic contexts for the containment of this important citrus pathogen.

1Sex steroid hormones are not exclusively localised in the circulation and can be found in numerous extragonadal tissues, in concentrations unrelated to the circulating fraction. Existing methodology to measure intramuscular steroid hormone concentrations includes both immune-based assays and liquid chromatography-mass spectrometry (LC-MS), the gold standard for hormone measurements. To date, no LC-MS based methods validation has been published on the measurement of intramuscular sex steroid hormones, despite clear biological relevance. Here, we describe the development and validation of a simple, high-throughput LC-MS Orbitrap method for the measurement of 10 intramuscular sex steroid hormones, including pregnenolone, progesterone, dehydroepiandrosterone, androstenedione, testosterone, epitestosterone, dihydrotestosterone, oestrone, oestradiol, and oestriol. In brief, isotope labelled standards were added to 5-6 milligrams of lyophilised muscle tissue, homogenised and extracted with ethyl acetate. The extracts were dried down and sequentially derivatised with 1-methylimidazole-2-sulfonyl chloride and hydroxylamine hydrochloride to target both the phenolic hydroxyl groups and ketone groups. The limit of detection was 1.0 {+/-} 1.0 pg/mg (range 0.36 - 3.26 pg/mg), with a R2 > 0.99 for all analytes. Matrix effects were 90-110% for all analytes except for dihydrotestosterone (143.6%), and precision was <10 CV% for all analytes in the presence of a muscle matrix. Our method allows for 20-40 samples to be prepared in [~]4 h, with a sample data acquisition time of 13 minutes. Moreover, our method provides the opportunity for specific analysis of steroid hormone concentrations in skeletal muscle, allowing target tissue specificity instead of relying on proxy measures from the circulation.

Background Oropouche virus (OROV) is an emerging vector-borne virus with rapidly expanding geographic range, increasing case counts, and growing evidence of severe outcomes including neuroinvasive disease and vertical transmission. Because OROV infection presents with nonspecific febrile illness that overlaps clinically with other viruses including dengue, zika, and chikungunya, accurate molecular diagnostics are essential for patient care and surveillance. Yet existing assays rely on single genomic targets and are vulnerable to detection failure as the virus evolves and reassorts. Methodology/Principal Findings To support diagnostic capacity, we developed and clinically validated a multiplexed qPCR assay targeting three regions of the OROV S segment, incorporating redundancy to preserve sensitivity across viral diversity while enabling robust clinical interpretation. The multiplex also includes an assay targeting RNaseP as an internal sample control to ensure adequate sample processing. We evaluated assay performance using both historical and contemporary OROV strains and validated the assay on contrived serum, plasma, and cerebrospinal fluid samples, assessing linearity, limit of detection (LOD), accuracy, specificity, precision, and sample stability. The assay met or exceeded all predefined acceptance criteria for clinical testing and achieved an LOD as low as 6 copies per reaction for contemporary outbreak strains. We further implemented a logic-based interpretation matrix that reduced false-positive risk while maintaining sensitivity near the analytical LOD. Conclusions/Significance Our assay sensitively and specifically detects OROV RNA in serum, plasma, and cerebrospinal fluid while incorporating safeguards against viral evolution and reassortment. The assay has been approved for use by CLIA at Nexus Medical Labs in 49 U.S. states, expanding access to timely OROV diagnostics in the United States and providing a durable framework for molecular detection of reassorting, rapidly evolving viruses as OROV continues to spread into new regions.

Adeno-associated virus (AAV) vectors are widely used in gene therapy, whereas low manufacturing efficiency and a large proportion of empty capsids are major obstacles. This study focused on the Yin Yang 1 (YY1) binding motif (YY1-motif) and investigated the effect of its presence or insertion at upstream of the Replicase (Rep)/Capsid Cap) gene on AAV vector production. We found that the YY1-motif incidentally presented in a Rep/Cap plasmid was associated with high vector production. We then designed several modified Rep/Cap (RC2) constructs. The YY1-motif insertion at the upstream of Rep/Cap gene increased vector yield in a repeat-number-dependent manner, and similar effects were not observed with other promoters insertion. Furthermore, the insertion of the YY1-motif reduced the amount of Cap protein per the same amount of full particle in supernatants on multiple serotypes, indicating the improvement in the empty/full capsid ratio. The YY1-motif insertion did not affect the AAV vector infectivity. These results denote that the YY1-motif has a universal regulatory function that optimizes the Rep/Cap expression balance, and simultaneously improves the production efficiency and full particle formation of AAV vectors. This finding could contribute to the development of highly efficient and high-quality AAV manufacturing processes.

Introduction: Synthetic oligopeptides provide a rapid and cost-efficient approach to developing antibodies and diagnostics for emerging viral variants. Methods: This study computationally and experimentally characterized a synthetic peptide analog of the SARS-CoV-2 spike subdomain 2 major disulfide loop (SD2MDL), designated S621 (CPVAIHADQLTPTWRVYSTC). Binding affinity was computationally estimated using the Heuristic Affinity Prediction Tool for Immune Complexes (HAPTIC), while experimental validation was performed using enzyme-linked immunosorbent assay (ELISA) with rabbit-derived antipeptide antibodies. Clinical diagnostic accuracy testing was done using plasma samples from RT-PCR-confirmed COVID-19 patients and pre-COVID-19 controls. Results: S621 demonstrated nanomolar binding affinity (Kdapp = 1.14 nM) and high avidity (3.67 nM), closely matching HAPTIC predictions (3.54 nM). Diagnostic evaluation yielded a sensitivity of 89.92% and specificity of 27.79%, corresponding to an overall accuracy of 71.79%. Discussion: These findings demonstrate that a single synthetic peptide derived from a conserved spike subdomain can function as a high-affinity surrogate for full-length antigens, supporting its potential application in rapid peptide-based immunodiagnostics.

Successive dengue virus (DENV) outbreaks can progressively reshape population immunity influencing disease expression and diagnostic performance. Objectives The aim was to evaluate the impact of secondary infections across sequential outbreaks on clinical severity, serotype dynamics and diagnostic concordance. Methods This retrospective study analyzed 976 febrile-stage samples from three sequential outbreaks in Misiones, Argentina. For serotyping and clinical analyses, 869 viremic samples confirmed by at least one direct method were included (2016: n=512; 2019: n=148; 2024: n=209). Additionally, 318 samples, including 107 non-viremic cases, were used to compare NS1 rapid diagnostic tests (NS1 Ag) and RT-PCR. Viral serotyping and clinical and laboratory markers of disease severity were evaluated. Results Secondary infections increased from 31.05% (2016) to 43.24% (2019) and 53.87% (2024) (p<0.0010). Serotype distribution shifted from DENV-1 predominance in 2016 (95.12%), DENV-1/DENV-4 co-circulation in 2019 (60.71%/39.29%), and DENV-2 predominance in 2024 (97.60%). Secondary infections were associated with more severe disease manifestations, particularly in 2024, with higher hematocrit (p=0.0120) and hemoglobin (p=0.0080), lower white blood cells (p=0.020) and platelet counts (p=0.0030), and elevated AST (p=0.0007) and ALT (p=0.0130). Concordance between NS1 Ag and RT-PCR was lower in secondary infections (k=0.457 vs k=0.759, p=0.0013). Conclusions The rising frequency of secondary infections may affect both clinical severity and diagnostic performance during outbreaks. The clinical impact was more evident in 2024, likely associated with the introduction of a new serotype. These findings highlight the need for optimized surveillance and diagnostic strategies to improve case detection and patient management during epidemics.

The catalytic rate constant (kcat) for product formation is considered a turnover number. Therefore, it is often mistakenly believed that kcat equals the turnover number and the number of substrate molecules changed per unit of time. Therefore, the aim of this study is to show that the rate constant for product synthesis and release is not always the same as the rate constant [Formula] for substrate utilization. To determine the precise substrate concentration at which these two rate constants are identical, it is appropriate to derive equations that allow the computation of [Formula]. In the end, the study will provide the most likely concentration of enzymes that can guarantee minimal or no recycling. An analysis of the literature on invertase (EC 3.2.1.26) and the Bernfeld method of generating Michaelian kinetic parameters for human salivary alpha-amylase (HSAA, EC 3.2.1.1) revealed that all kinetic parameters except [Formula] increased with substrate concentration. Meanwhile, the values for invertase decreased from 0.0697 to 0.0361/min, and the values for HSAA decreased from 5,802.4687 to 3,213.0124/min. The magnitude of [Formula] for each substrate concentration ([ST]) is not always equal, except when [ST] is determined post-assay by computation or extrapolation. The lower [ST] at which [Formula] and kcat for [HSAA] are equal is 3.667540128 g/L (5.682584642 M), which is similar to the molarity of HSAA (5.6101967709 M). The kcat for HSAA was 11,930.9885/min. Future assays should aim to generate large amounts of data for a robust statistical analysis. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=164 SRC="FIGDIR/small/728646v1_ufig1.gif" ALT="Figure 1"> View larger version (36K): org.highwire.dtl.DTLVardef@c49b65org.highwire.dtl.DTLVardef@1b60655org.highwire.dtl.DTLVardef@159ba67org.highwire.dtl.DTLVardef@1dce0af_HPS_FORMAT_FIGEXP M_FIG C_FIG

Tacrolimus is an immunosuppressant drug commonly used in transplantation. Although multiple studies have demonstrated that polymorphisms in the CYP3A5 gene impact the metabolism of tacrolimus, routine pre-transplant testing for these markers is still not broadly implemented. TacroType - a new laboratory developed test implemented by One Lambda Laboratories - utilizes a qPCR-based six-plex assay for CYP3A5 genotyping and detects the three most common genetic variants (*3, *6 and *7) associated with loss of CYP3A5 protein function and reduced tacrolimus metabolism. TacroType was optimized to address known sources of protocol, technical or sample variability to achieve accurate and reproduceable genotyping results. An analytical performance study was completed following CLSI guidelines. Accuracy was confirmed for each possible CYP3A5 genotype involving 6 target alleles using 32 well-characterized reference samples. TacroType exhibited accurate performance within a broad range of DNA concentrations and quality. Precision studies indicated consistent genotyping results across 4 operators, 2 instrument types and 5 lots of reagents. Accurate and reproducible assay performance was demonstrated using whole blood from 100 and buccal swabs from 70 donors. The analytical performance of TacroType was evaluated in 4014 total qPCR reactions, with a report rate of 99.8% and genotyping accuracy of 100% (95% confidence interval of 99.9%).

Fucoidans have been widely reported to show SARS-CoV-2 antiviral activity. In this study, we observed a striking difference in the inhibitory potency between two commercially available fucoidans: Fucus vesiculosus crude (Fvc) and pure (Fvp). SEC-MALS analysis revealed two molecular weight populations for Fvc (1098 kDa, 58.58 kDa) and one for Fvp (40.48 kDa). At micromolar concentrations of fucoidans, the binding affinities (KDs) of Fvc_1098 (223 nM) and Fvc_58 (4.27 {micro}M) for the amine-biotinylated SARS-CoV-2 receptor binding domain (RBD) were higher than that of Fvp (76.5 {micro}M). At nanomolar concentrations, binding was observed only to the Avi-tag-, but not amine-biotinylated RBDs, suggesting better accessibility of their binding sites. The association rates (kon) were faster for Fvc than for Fvp. Similarly, affinities of Fvc_1098 (23.4 nM) and Fvc_58 (4.48 M) for ACE2 were greater than that of Fvp (66.8 M), indicating that Fvc can bind directly to both RBD and ACE2. Fvc demonstrated enhanced inhibitory potency (IC50 = 58 g/mL) compared to Fvp (IC50 > 239 g/mL) in the pseudovirus entry assay and did not induce cytotoxicity in HEK293T cells. In conclusion, crude fucoidan with high fucose content and high molecular weight shows promising antiviral activity.

Tomato brown rugose fruit virus (Tobamovirus fructirugosum) is an emerging virus that affects tomatoes, capsicum, and chili. Since its first detection in Jordan in 2015, the virus was reported in more than 40 countries across all the continents. In Morocco, the virus was reported for the first time in October 2021. However, its genetic diversity remains unexplored. In this work, we used a collection of tomato fruits from local markets to investigate the variability of the virus in the country. We explored the different pressures acting on the N-terminus of the RNA-dependent RNA polymerase, the movement protein, and the coat protein genes. Then, we used haplotype network analyses to reveal the population structure within the Moroccan isolates and studied their relationships with the ones from the world. We found that genetic diversity is low, which is consistent with the global situation. No signatures of diversifying selection were detected across the analyzed genes. However, the virus sequences from Morocco showed a clear geographic structure, suggesting that geographic factors probably combined with agricultural practices may contribute to shaping the population structure of ToBRFV in Morocco.

Enteroviruses (EVs) are ubiquitous contaminants of surface waters, where they can remain infectious for long periods of time. Most methods used for EV monitoring are unable to distinguish between infectious and non-infectious particles or between EV types. Because different types exhibit both distinct environmental persistence and health implications, there is a need for type-resolved infectivity measurements. Here we developed Integrated Cell Culture-Nanopore Sequencing (ICC-NanoporeSeq), a method combining short-term cell culture amplification with Nanopore sequencing of the VP1 gene. The ICC approach was adapted from a previously described ICC-RTqPCR protocol, while the NanoporeSeq workflow was derived from a clinical EV typing protocol and optimized for environmentally circulating EV types. Using samples containing known concentrations of ten EV types, the NanoporeSeq method accurately and reproducibly recovered the original proportions of all EV types after correction of biases. Furthermore, type-specific calibration curves generated with ICC-NanoporeSeq enabled quantification of the infectious concentrations of six EV types, allowing a simultaneous and type-resolved assessment of infectivity in mixed samples. Overall, ICC-NanoporeSeq provides a scalable approach for the parallel analysis of multiple EV types. Compared with the predecessor ICC-RTqPCR method, it eliminates the need for multiple type-specific PCR primers and can therefore be readily expanded to include additional EV types. IMPORTANCECurrent methods used to detect EVs in environmental samples generally measure viral genome copies without determining whether viruses remain infectious, limiting their use in public health risk assessment or water quality monitoring. At the same time, available infectivity assays are often labor-intensive and cannot distinguish between different EV types. Here, we developed ICC-NanoporeSeq, a method combining cell culture and Nanopore sequencing to simultaneously quantify the infectious concentrations of multiple EV types in samples containing mixed EV populations. The method provides an efficient and scalable approach for studying EVs in complex environmental matrices. ICC-NanoporeSeq has potential applications in wastewater-based epidemiology, environmental surveillance, and disinfection studies, where understanding the persistence of different EV types simultaneously is crucial.

Rapid, portable detection of multiple nucleic acid targets is essential for infectious disease surveillance and precision oncology. CRISPR-based diagnostics have set a high bar for sensitivity and single-base specificity, yet their reliance on collateral nuclease activity complicates multiplexing, integration with amplification, and point-of-care deployment. Here we present TIMBER (Templated Incision Mediated By Endonucleases of Repair), a non-CRISPR, isothermal platform that achieves comparable performance without nonspecific nuclease activity. TIMBER uses a repair endonuclease to cleave probes containing abasic sites only when they are hybridized to a matched target. The system exhibits strong specificity, enabling single-nucleotide polymorphism discrimination. TIMBER provides an analytical limit of detection 12 pM without preamplification or 1 copy per {micro}L (1.6 aM) with preamplification through RT-PCR or RT-LAMP, with results observable by visual fluorescence or on lateral flow. We deploy TIMBER to detect SARS-CoV-2 in clinical saliva samples and further demonstrate multiplex detection of four targets enabling identification of EGFR mutations in lung cancer samples. This approach offers a flexible, rapid, and low-instrument ready solution for diverse nucleic acid diagnostics, from viral detection to cancer genotyping.

Trichophyton mentagrophytes genotype VII (TmVII) is an emerging sexually transmitted dermatophyte that causes skin infections characterized by inflammatory, erythematous-squamous, painful, and persistent lesions. This genotype is part of the T. interdigitale/T. mentagrophytes Species Complex (TiTmSC), which comprises 28 genotypes. To enable rapid and specific differentiation of TmVII from other genotypes, a real-time polymerase chain reaction (rt-PCR) assay was developed targeting three unique single-nucleotide polymorphisms in the ITS1 region of TmVII. Assay specificity was further improved by introducing an additional mismatch at the 3 ends of both forward and reverse primers. The rt-PCR assay demonstrated high sensitivity, with a detection limit of 0.0002 ng of TmVII genomic DNA. The assay was highly specific, with no cross-reactivity observed with either closely or distantly related fungal pathogens when a cycle threshold (Ct) cutoff of 37 was applied. Among 497 mold isolates tested, 47 were confirmed as TmVII by rt-PCR, and the results were fully concordant with conventional ITS-PCR/Sanger sequencing. The rt-PCR assay demonstrated high sensitivity, specificity, reproducibility, and speed, with a turnaround time of one day after DNA extraction, compared with seven to ten days for Sanger sequencing. The first rapid molecular assay developed using TaqMan chemistry for TmVII identification is expected to enhance patient care and support infection control measures.

Tuberculosis (TB) remains one of the deadliest infectious diseases, with over a million deaths annually and a growing threat from multidrug-resistant strains (MDR-TB). A major bottleneck in controlling TB is the lack of truly portable, rapid, and user-friendly diagnostic systems that can operate effectively in decentralized, resource-constrained settings. Here, we present a first-of-its-kind, portable nucleic-acid-based diagnostic platform that enables both primary TB screening and detection of drug resistance within the same unified framework, without any change in the operative embodiment. The system integrates loop-mediated isothermal amplification (LAMP) targeting dual Mycobacterium tuberculosis markers (IS6110 and IS1081) with a compact, AI-enabled device and smartphone-based readout, delivering rapid and reliable results at the point-of-care. Clinical evaluation across 105 samples demonstrated high sensitivity and specificity. Further validation through real-world deployment in a primary healthcare setting, using a single-gene (IS6110) configuration operated by minimally trained personnel, yielded 95.60% sensitivity and 100% specificity, benchmarked against GeneXpert. Critically, the same platform architecture, without modification, extends seamlessly to drug-resistance profiling, demonstrated here through a probe-free, allele-specific LAMP approach for identifying key mutations associated with rifampicin (rpoB) and isoniazid (katG) resistance. By combining robust molecular diagnostics with AI-driven automation in a compact and accessible format, this work represents a significant medical advancement toward democratizing TB care. The platform thus holds strong potential to enable early screening, guide timely treatment decisions, reduce transmission, and substantially strengthen global TB elimination efforts, particularly in high-burden, low-resource settings.

Accurate quantitation of therapeutic bacteriophages (phages) remains a challenge for clinical development. Plaque-based enumeration is the current standard but is laborious, host-dependent, and variable, particularly when distinguishing individual phages in cocktails. Targeted mass spectrometry of virion structural proteins offers an orthogonal, structure-based approach amenable to reproducible and scalable phage quantitation. Here, we describe a targeted proteomic liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay for host-independent quantitation of the Pseudomonas aeruginosa podovirus LUZ19. Proteomic characterization was performed on an LTQ Orbitrap XL to assess sequence coverage and select surrogate peptide candidates based on specificity and sensitivity. High-resolution peptide mapping identified multiple structural proteins of LUZ19 and provided 55% sequence coverage for the major head protein (YP_001671977.1). Fifteen peptides were detected and evaluated, from which the tryptic peptide EVAELDGQELAR was selected based on abundance, stability, and chromatographic performance. Quantitative analysis was conducted on a QTRAP 7500+ using optimized multiple reaction monitoring transitions for targeted peptide detection. Back-calculated concentrations met accuracy criteria across a validated range of 0.008 to 80 pg/mL, with bias spanning -8.2 to 8.2%, intra-day precision ranging from 0.5 to 9.8%, and inter-day precision ranging from 6.3 to 9.7%. Peptide concentrations from digested lysate samples were related to phage concentrations determined by double layer agar assay, yielding an estimated three copies of the major head protein per virion. ImportanceBacteriophages are the most abundant biological entities on the planet and represent a promising therapeutic class for combating drug-resistant bacterial infections. Realizing the clinical potential of bacteriophage therapy requires analytical methods capable of meeting the standards of modern drug development. Targeted mass spectrometry offers unmatched specificity and resolution for precise quantitation of individual bacteriophages within complex biological samples, a capability that conventional enumeration methods cannot match. Only one prior study has applied mass spectrometry to bacteriophage quantitation, using a well-characterized model bacteriophage at a single concentration without calibration or a validated analytical range. Using Pseudomonas aeruginosa podovirus LUZ19, we present the first targeted mass spectrometry-based bacteriophage quantitation assay developed and validated following FDA bioanalytical guidance. This work establishes a rigorous analytical foundation that moves bacteriophage therapy closer to the standards required for informed dose selection, candidate evaluation, and clinical development.

Measles virus remains a significant global health threat, and despite the availability of an effective vaccine, measles cases continue to increase worldwide in recent years. Genomic surveillance has become an essential tool for monitoring virus circulation and investigating outbreaks. Here, we describe a wet-laboratory method for whole-genome sequencing of measles virus using a tiled amplicon approach and Illumina sequencing technology. A previously published Oxford Nanopore-based tiled primer scheme was adapted to include both circulating measles genotypes and for use on the Illumina platform. Two Illumina library preparation kits, Illumina DNA Prep (IDP) and Nextera XT (XT), were evaluated for performance. The IDP kit demonstrated more complete genomes and consistent genome coverage compared with XT. Using quantified reference genomes, the limit of detection was determined to be 10,000 genome copies for genotype B3 and D8. Sequence accuracy was evaluated using previously characterized clinical samples and showed high concordance. This method provides a reliable and sensitive approach for measles virus whole-genome sequencing using Illumina platforms and is suitable for genomic surveillance applications.

Molecular diagnostics to detect Vibrio cholerae (Vc) may be negatively impacted by pathogen-specific lytic bacteriophage (phage) predation. To address this problem, phage detection as a proxy for pathogen detection has been proposed. However, efforts to modernize cholera diagnostics with molecular tools require addressing knowledge gaps on best practices to detect Vc and associated bacteriophages. We conducted polymerase chain reaction (PCR), quantitative PCR (qPCR), and nano-liter (nl) qPCR targeting Vc and known phages (ICP1/2/3) on stool samples collected from patients admitted at hospitals across Bangladesh. Of 4,975 patients enrolled, 2,574 diarrheal samples were collected and over 65,000 reactions were conducted, including replicates. We analyzed the results for target-specific assay alignment and then used machine learning to determine the effect of phage predation on Vc-assay alignment. Standard curve analyses were used to set qPCR-positivity thresholds at 7.3x105 CFU/mL for Vc and 1.7x103, 9.3x103, and 3.0x105 PFU/mL for ICP1, ICP2, and ICP3, respectively. Among 2,462 samples assayed by qPCR, target detection was 25.3% (623), 7.8% (193), 0.5% (13), and 5.8% (144) for Vc, ICP1, ICP2, and ICP3, respectively. There was strong alignment between assays for Vc detection ({kappa}=0.785) and moderate alignment for phage detection ({kappa}=0.609, 0.593, and 0.533 for ICP1/2/3, respectively). Phages were ranked as the first (ICP1) and third (ICP3) effectors of Vc diagnostic alignment. These findings provide insights on how to prioritize molecular methods in the cholera field as well as related less tractable diseases facing similar diagnostic challenges. IMPORTANCEThis paper presents a comprehensive comparison of molecular methods to detect Vibrio cholerae (Vc) and associated bacteriophage (phage) which can be used as a proxy for pathogen detection. This initiative is an important step towards modernizing cholera diagnostics with molecular tools. In this study, we found that quantitative polymerase chain reaction (qPCR) represents a reasonable approach to detect Vc and associated phages balancing assay performance, cost, and accessibility. A key additional finding was that phage predation was found to be a leading factor that impacts the alignment of molecular methods to detect Vc. While we recommend qPCR be added to the cholera diagnostic toolkit, the effects of phage predation need to be accounted for in the development and evaluation of cholera diagnostics. These findings have applicability to less tractable disease where diagnostics share similar vulnerabilities.

Native mass spectrometry (nMS) is well established for measuring protein masses and stoichiometries using nano-electrospray ionization (nESI), yet salt adduction and source activation energies can limit routine measurements. In this study, we benchmark submicron quartz nanopipette nESI emitters (<50 nm internal diameter) across three mass spectrometry platforms (quadrupole-time-of-flight, quadrupole-Orbitrap, and tribrid-Orbitrap platforms) and a wide protein mass range (17-800 kDa). We analysed holo-myoglobin (17 kDa) over a range of concentrations (10 M-10 nM) and capillary voltages to determine limits of detection and define a gentle operating regime. We additionally observe reduced Na+ adduction and preservation of the Zn2+-bound metalloproteoform of carbonic anhydrase II (29 kDa). Proteins and protein complexes spanning the mid-to-high mass range including ovalbumin ([~]44 kDa), malate dehydrogenase ([~]70 kDa), glutamate dehydrogenase ([~]350 kDa), {beta}-galactosidase ([~]465 kDa), and GroEL ([~]800 kDa), were readily detected using nanopipette emitters. Compared with conventional 1-2 m internal diameter borosilicate emitters, quartz nanopipettes provided higher signal-to-noise ratios and fewer adducts. Finally, direct analysis of clarified bacterial lysate expressing -synuclein yielded a clear monomeric charge-state distribution, demonstrating compatibility with complex biological matrices. Collectively, these results establish quartz nanopipette nESI as an instrument-portable, salt-tolerant approach suitable for routine nMS analysis across a broad range of protein molecular weights and sample complexities.

BackgroundThe global rise of multidrug-resistant (MDR) bacteria represents a critical public health threat, and Romania ranks amongst the most affected countries in Europe. As conventional therapy increasingly fails, bacteriophage therapy has re-emerged as a promising alternative to antibiotics. Urban rivers, contaminated with resistant bacterial strains, represent an underexplored and accessible reservoir for the isolation of lytic phages with therapeutic potential. MethodsTwo bacteriophages, 17M_Ec17_D and 22C_Ec22_D, were isolated from the Dambovita River, Bucharest, Romania, using MDR E. coli as host bacteria. Phage characterization included plaque morphology, transmission electron microscopy, and host range assessment by spot assay against 30 MDR E. coli isolates. Whole genome sequencing was performed on Illumina MiSeq and Oxford Nanopore Technologies MinION platforms, followed by bioinformatic analysis including taxonomic classification, lifestyle prediction, and functional annotation. ResultsBoth phages formed clear plaques and were classified as Kayfunavirus (17M_Ec17_D, Podoviridae-like) and Kagunavirus (22C_Ec22_D, Siphoviridae-like) with nucleotide similarities of 89.2% and 71.4% to their closest relatives, respectively, suggesting both are candidates for novel species. Host range analysis revealed lytic activity against 13% and 10% of tested MDR isolates, with complementary infection profiles. Genomic analysis confirmed a strictly lytic lifestyle for both phages, supported by the presence of holin and spanin genes and the absence of lysogenic modules, antibiotic resistance genes, and virulence factors. ConclusionsTo the best of our knowledge, this is the first study conducted in Romania to isolate and genomically characterize lytic bacteriophages targeting MDR E. coli. The characterized phages represent safe therapeutic candidates whose complementary host ranges suggest potential application as part of phage cocktail to broaden antimicrobial coverage against MDR infections.