Multiplex Real-time RT-PCR Research Articles

B-201 Clinical Performance Evaluation of IRON-qPCR™ RV, a Novel Molecular POCT system, for the Qualitative Detection of Respiratory Viruses in Nasopharyngeal Swab

Abstract Background The availability of Point-of-Care testing (POCT) based on molecular diagnostics to test simultaneously for multiple respiratory viruses is very limited though significant progress has been made in molecular testing for COVID-19 during the pandemic. Considering the similar symptoms presented by patients infected with various respiratory pathogens, it is crucial to have multiple POCT systems capable of detecting multiple respiratory pathogens while distinguishing SARS-CoV-2 from other pathogens. To meet the growing demand for multiplex testing for respiratory pathogens, a molecular POCT, IRON-qPCR™ RV has been developed. IRfON-qPCR™ RV is a multiplex real-time RT-PCR assay designed for the qualitative detection and differentiation of SARS-CoV-2, Influenza A, Influenza B, RSV-A, and RSV-B RNA from human nasopharyngeal swab specimens. The IRON-qPCR™ proceeds the entire process automatically from nucleic acid extraction to real-time RT-PCR within 40 minutes. The main goal of this study is to evaluate the clinical performance of IRON-qPCR™ RV in comparison with other assays and kits using nasopharyngeal swab samples. Methods To assess the clinical performance of the IRON-qPCR™ RV, specimen collection and evaluation were conducted at a clinical institution in France, utilizing a total of 980 nasopharyngeal swab samples. The comparators used were the Xpert® Xpress CoV-2/Flu/RSV plus Kit and the RealStar® RSV RT-PCR Kit 3.0. Since RSV subtypes are not distinguished by the Xpert kit, all RSV without subtype distinction were compared. Additionally, RealStar kit was used to compare the results of IRON-qPCR™ RV for RSV subtypes A and B. Clinical samples showing discrepancies between Xpert and RealStart, and the IRON-qPCR™ RV were further analyzed using Allplex™ SARS-CoV-2/FuA/FluB/RSV Assay and sequencing. Results Through the comparison of clinical performance of the IRON-qPCR™ RV with Xpert for SARS-CoV-2, Influenza A, and Influenza B in nasopharyngeal swab samples, the clinical sensitivity was analyzed to be over 95.5%, and the clinical specificity was over 99.6%. For RSV, compared to Xpert, the clinical sensitivity was analyzed to be 96.9%, and the clinical specificity was 98.9%. Furthermore, in comparison with RealStar, the clinical sensitivity and specificity of IRON-qPCR™ RV for RSV-A were determined to be 96.2% and 100%, respectively, and the clinical sensitivity and specificity for RSV-B were 96.0% and 100%. Additionally, discrepant samples in comparison with Xpert were further tested using the Allplex as a resolver kit. The result showed that the clinical sensitivity and specificity of IRON-qPCR™ RV for SARS-CoV-2, Influenza A, and Influenza B were over 98.3% and 100%. For RSV, the clinical sensitivity and specificity were 99.5% and 99.1%. Conclusions The clinical performance of IRON-qPCR™ RV was analyzed with the clinical sensitivity of over 95% and the clinical specificity of over 99%. Upon analysis including the results of the resolver kit for discrepant samples, increased clinical sensitivity and specificity were determined. The results of this study strongly support that the IRON-qPCR™ RV is a reliable POCT system for the simultaneous detection and differentiation of multiple respiratory viruses. Furthermore, it is applicable to district hospitals as well as clinical laboratories for accurate and timely testing.

B-207 Clinical Evaluation of ExiStation™ FA 96 RV for the detection of human respiratory viruses in human nasopharyngeal swab specimen

Abstract Background There has been growing demand for fully automated multiplex testing of respiratory viruses in molecular diagnostics following the COVID-19 pandemic. ExiStation™ FA 96 RV developed by BIONEER is a multiplex real-time RT-PCR assay. It is designed for the simultaneous detection and differentiation of SARS-CoV-2, Influenza A, Influenza B, and RSV RNA in human nasopharyngeal swab specimens from individuals showing signs and symptoms of respiratory viral infection. ExiStation™ FA 96 automates the entire process from RNA extraction to real-time RT-PCR for up to 96 samples at once within 100 minutes. Moreover, the system is equipped to decap sample tubes, eliminating the need for handling sample transport media. In this study, the clinical performance of the ExiStation™ FA 96 RV assay was evaluated using nasopharyngeal swab samples. Methods Nasopharyngeal swab samples, totaling 859 samples, are collected according to the procedures by the clinical institution in France and preserved in Virus transport media. Once anonymized and randomly allocated, the swab transport media tube, without capping procedure, are directly placed onto the ExiStation™ FA 96. Subsequently, both extraction and real-time RT-PCR are automatically processed. Clinical sensitivity, specificity, and agreement are analyzed by comparing results with confirmatory reagents SARS-CoV-2 RT-qPCR Reagent Kit, PKAmp™ Respiratory SARS-CoV-2 RT-PCR Panel Kit, and Bosphore SARS-CoV-2/Flu/RSV Panel Kit, as well as comparator reagent Allplex™ Respiratory Panel 1 and Allplex™ SARS-CoV-2 Assay. Results The comparison between confirmatory reagents and the ExiStation™ FA 96 RV resulted in a clinical sensitivity of at least 96.4% (164/164 for SARS-CoV-2, 64/65 for Influenza A, 74/75 for Influenza B, and 53/55 for RSV) and a clinical specificity of 100% (500/500 for all targets). When compared with the comparator reagent, the overall agreement and Cohen's kappa value were both determined to be above 99.1% and 0.989, respectively (664/664 for SARS-CoV-2, 564/565 for Influenza A, 573/575 for Influenza B, and 550/555 for RSV). Additionally, any discrepant samples identified in comparison with the comparator reagent were verified through sequencing analysis. Upon sequencing analysis on a total of 8 samples and aligning the confirmed results with the analysis content, no alterations observed in the analysis of clinical sensitivity and specificity. Conclusions The evaluation of the ExiStation™ FA 96 RV assay showed outstanding clinical performance in detecting four respiratory viruses, SARS-CoV-2, Influenza A, Influenza B, and RSV, with high sensitivity and specificity. This study supports that the ExiStation™ FA 96 RV assay is a reliable tool for simultaneous molecular diagnostics of various respiratory infections in clinical laboratories.

Development and validation of highly sensitive multiplex real-time RT-PCR assay for detection of classical swine fever virus genome

Classical swine fever (CSF) remains a challenge for pig farming industrial lover the world despite the measures taken. The last CS case in the Russian Federation was reported in 2020, however, the threat of the disease emerging still persists. A set of anti-epidemic measures including mainly preventive vaccination and annual diagnostic monitoring using molecular-genetic and serological methods is required for CSF virus introduction prevention and rapid eradication of potential disease out breaks. Therefore, areal-time reverse transcription-polymerase chain reaction using an internal control sample has been developed. Therefore, areal time reverse transcription-polymerase chain reaction using an internal control sample has been developed. Modified primers (locked nucleic acids containing conformationally blocked nucleosides) providing a higher affinity to the DNA matrix and physico-chemical stability and a FAM-labeled TaqMan probe were selected for 5’-untranslatedregion of the genome. The following validation parameters were defined: accuracy, repeatability, reproducibility, specificity and sensitivity. For comparative analysis of the developed as say sensitivity, swabs, samples of organs and tissues collected from pigs experimentally infected with an epizootic strain of the classical swine fever virus (spleen, kidney, liver, blood, lymph nodes, rectal and oral smears), animal-contaminated feed and virus-containing material with known virus titres were also tested in parallel with coded test systems No. x1 andx2. The developed assay was shown to have 100% diagnostic sensitivity and detection limit of 0,23 lgCCID50/cm3. Therewith, there sults of analysis of test systems No. x1, x2 based on above parameters were lower that could give rise to false positive real-time RT-PCR results and incorrect diagnosis. Thus, described assay can be used for extensive monitoring of classical swine fever in the Russian Federation

Resurgence of influenza with increased genetic diversity of circulating viruses during the 2022-2023 season.

Introduction. After two seasons of absence and low circulation, influenza activity increased significantly in the winter of 2022-2023. This study aims to characterize virological and epidemiological aspects of influenza infection in Bulgaria during the 2022-2023 season and perform a phylogenetic/molecular analysis of the hemagglutinin (HA) and neuraminidase (NA) sequences of representative influenza strains.Hypothesis/Gap Statement. Influenza A and B viruses generate new genetic groups/clades each season, replacing previously circulating variants. This results in increased antigenic distances from current vaccine strains. Strengthening existing influenza surveillance is essential to meet the challenges posed by the co-circulation of influenza and SARS-CoV-2.Methodology. We tested 2713 clinical samples from patients with acute respiratory illnesses using a multiplex real-time RT-PCR kit (FluSC2) to detect influenza A/B and Severe acute respiratory syndrome coronavirus-2(SARS-CoV-2) simultaneously. Representative Bulgarian influenza strains were sequenced at the WHO Collaborating Centres in London, UK, and Atlanta, USA.Results. Influenza virus was detected in 694 (25.6 %) patients. Of these, 364 (52.4 %), 213 (30.7 %) and 117 (16.9 %) were positive for influenza A(H1N1)pdm09, A(H3N2) and B/Victoria lineage virus, respectively. HA genes of the 47 influenza A(H1N1)pdm09 viruses fell into clades 5a.2. and 5a.2a.1 within the 6B.5A.1A.5a.2 group. Twenty-seven A(H3N2) viruses belonging to subclades 2b, 2a.1, 2a.1b and 2a.3a.1 within the 3C.2a1b.2a.2 group were analysed. All 23 sequenced B/Victoria lineage viruses were classified into the V1A.3a.2 group. We identified amino acid substitutions in HA and NA compared with the vaccine strains, including several substitutions in the HA antigenic sites.Conclusion. The study's findings showed genetic diversity among the influenza A viruses and, to a lesser extent, among B viruses, circulating in the first season after the lifting of anti-COVID-19 measures.

Characteristics and evolution of hemagglutinin and neuraminidase genes of Influenza A(H3N2) viruses in Thailand during 2015 to 2018.

Influenza A(H3N2) virus evolves continuously. Its hemagglutinin (HA) and neuraminidase (NA) genes have high genetic variation due to the antigenic drift. This study aimed to investigate the characteristics and evolution of HA and NA genes of the influenza A(H3N2) virus in Thailand. Influenza A positive respiratory samples from 2015 to 2018 were subtyped by multiplex real-time RT-PCR. Full-length HA and NA genes from the positive samples of influenza A(H3N2) were amplified and sequenced. Phylogenetic analysis with the maximum likelihood method was used to investigate the evolution of the virus compared with the WHO-recommended influenza vaccine strain. Homology modeling and N-glycosylation site prediction were also performed. Out of 443 samples, 147 (33.18%) were A(H1N1)pdm09 and 296 (66.82%) were A(H3N2). The A(H3N2) viruses circulating in 2015 were clade 3C.2a whereas sub-clade 3C.2a1 and 3C.2a2 dominated in 2016-2017 and 2018, respectively. Amino acid substitutions were found in all antigenic sites A, B, C, D, and E of HA but the majority of the substitutions were located at antigenic sites A and B. The S245N and N329S substitutions in the NA gene affect the N-glycosylation. None of the mutations associated with resistance to NA inhibitors were observed. Mean evolutionary rates of the HA and NA genes were 3.47×10 -3 and 2.98×10-3 substitutions per site per year. The influenza A(H3N2) virus is very genetically diverse and is always evolving to evade host defenses. The HA and NA gene features including the evolutionary rate of the influenza A(H3N2) viruses that were circulating in Thailand between 2015 and 2018 are described. This information is useful for monitoring the genetic characteristics and evolution in HA and NA genes of influenza A(H3N2) virus in Thailand which is crucial for predicting the influenza vaccine strains resulting in high vaccine effectiveness.

Development and evaluation of a multiplex real-time RT-PCR assay for simultaneous detection of H5, H7, and H9 subtype avian influenza viruses

H5, H7 and H9 are the major subtypes of avian influenza virus (AIV) that cause economic losses in the poultry industry and sporadic zoonotic infection. Early detection of AIV is essential for preventing disease spread. Therefore, molecular diagnosis and subtyping of AIV via real-time RT-PCR (rRT-PCR) is preferred over other classical diagnostic methods, such as egg inoculation, RT-PCR and HI test, due to its high sensitivity, specificity and convenience. The singleplex rRT-PCRs for the Matrix, H5 and H7 gene used for the national surveillance program in Korea have been developed in 2017; however, these methods were not designed for multiplexing, and does not reflect the sequences of currently circulating strains completely. In this study, the multiplex H5/7/9 rRT-PCR assay was developed with sets of primers and probe updated or newly designed to simultaneously detect the H5, H7 and H9 genes. Multiplex H5/7/9 rRT-PCR showed 100% specificity without cross-reactivity with other subtypes of AIVs and avian disease-causing viruses or bacteria, and the limit of detection was 1–10 EID50/0.1 ml (50% egg infectious dose). Artificial mixed infections with the three different subtypes could be detected accurately with high analytical sensitivity even under highly biased relative molecular ratios by balancing the reactivities of each subtype by modifying the concentration of the primers and probes. The multiplex H5/7/9 rRT-PCR assay developed in this study could be a useful tool for large-scale surveillance programs for viral detection as well as subtyping due to its high specificity, sensitivity and robustness in discriminating viruses in mixed infections, and this approach would greatly decrease the time, cost, effort and chance of cross-contamination compared to the conventional method of testing three subtypes by different singleplex rRT-PCR methods in parallel or in series.

Geographical Expansion of Avian Metapneumovirus Subtype B: First Detection and Molecular Characterization of Avian Metapneumovirus Subtype B in US Poultry.

Avian metapneumovirus (aMPV), classified within the Pneumoviridae family, wreaks havoc on poultry health. It typically causes upper respiratory tract and reproductive tract infections, mainly in turkeys, chickens, and ducks. Four subtypes of AMPV (A, B, C, D) and two unclassified subtypes have been identified, of which subtypes A and B are widely distributed across the world. In January 2024, an outbreak of severe respiratory disease occurred on turkey and chicken farms across different states in the US. Metagenomics sequencing of selected tissue and swab samples confirmed the presence of aMPV subtype B. Subsequently, all samples were screened using an aMPV subtype A and B multiplex real-time RT-PCR kit. Of the 221 farms, 124 (56%) were found to be positive for aMPV-B. All samples were negative for subtype A. Six whole genomes were assembled, five from turkeys and one from chickens; all six assembled genomes showed 99.29 to 99.98% nucleotide identity, indicating a clonal expansion event for aMPV-B within the country. In addition, all six sequences showed 97.74 to 98.58% nucleotide identity with previously reported subtype B sequences, e.g., VCO3/60616, Hungary/657/4, and BR/1890/E1/19. In comparison to these two reference strains, the study sequences showed unique 49-62 amino acid changes across the genome, with maximum changes in glycoprotein (G). One unique AA change from T (Threonine) to I (Isoleucine) at position 153 in G protein was reported only in the chicken aMPV sequence, which differentiated it from turkey sequences. The twelve unique AA changes along with change in polarity of the G protein may indicate that these unique changes played a role in the adaptation of this virus in the US poultry. This is the first documented report of aMPV subtype B in US poultry, highlighting the need for further investigations into its genotypic characterization, pathogenesis, and evolutionary dynamics.

Development and Optimization of a Multiplex Real-Time RT-PCR to Detect SARS-CoV-2 in Human Samples.

PCR and its variants (RT-PCR and qRT-PCR) are valuable and innovative molecular techniques for studying nucleic acids. qPCR has proven to be highly sensitive, efficient, and reproducible, generating reliable results that are easy to analyze. During the COVID-19 pandemic, qPCR became the gold standard technique for detecting the SARS-CoV-2 virus that allowed to confirm the infection event, and those asymptomatic ones, and thus save millions of lives. In-house multiplex qPCR tests were developed worldwide to detect different viral targets and ensure results, follow the infections, and favor the containment of a pandemic. Here, we present the detailed fundamentals of the qPCR technique based on fluorogenic probes and processes to develop and optimize a successful multiplex RT-qPCR test for detecting SARS-CoV-2 that could be used to diagnose COVID-19 accurately.

Development of a Novel Multiplex PCR Method for the Rapid Detection of SARS-CoV-2, Influenza A Virus, and Influenza B Virus.

A sensitive and specific multiplex fluorescence rapid detection method was established for simultaneous detection of SARS-CoV-2, influenza A virus, and influenza B virus in a self-made device within 30 min, with a minimum detection limit of 200 copies/mL. Based on the genome sequences of SARS-CoV-2, influenza A virus (FluA), and influenza B virus (FluB) with reference to the Chinese Center for Disease Control and Prevention and related literature, specific primers were designed, and a multiplex fluorescent PCR system was established. The simultaneous and rapid detection of SARS-CoV-2, FluA, and FluB was achieved by optimizing the concentrations of Taq DNA polymerase as well as primers, probes, and Mg2+. The minimum detection limits of the nucleic acid rapid detection system for SARS-CoV-2, FluA, and FluB were evaluated. By optimizing the amplification system, the N enzyme with the best amplification performance was selected, and the optimal concentration of Mg2+ in the multiamplification system was 3 mmol/L; the final concentrations of SARS-CoV-2 NP probe and primer were 0.15 μmol/L and 0.2 μmol/L, respectively; the final concentrations of SARS-CoV-2 ORF probe and primer were both 0.15 μmol/L; the final concentrations of FluA probe and primer were 0.2 μmol/L and 0.3 μmol/L, respectively; the final concentrations of FluB probe and primer were 0.15 μmol/L and 0.25 μmol/L, respectively. A multiplex real-time quantitative fluorescence RT-PCR system for three respiratory viruses of SARS-CoV-2, FluA, and FluB was established with a high amplification efficiency and sensitivity reaching 200 copies/mL for all samples. Combined with the automated microfluidic nucleic acid detection system, the system can achieve rapid detection in 30 minutes.

Testing the limits of multiplex respiratory virus assays for SARS-CoV-2 at high cycle threshold values: Comparative performance of cobas 6800/8800 SARS-CoV-2 & Influenza A/B, Xpert Xpress SARS-CoV-2/Flu/RSV, and cobas Liat SARS-CoV-2 & Influenza A/B.

Multiplex real-time RT-PCR assays for respiratory pathogens are valuable tools to optimize laboratory workflow and turnaround time. At a time when resurgence of influenza and respiratory syncytial virus (RSV) cases have been widely observed along with continued transmission of SARS-CoV-2, timely identification of all circulating respiratory viruses is crucial. This study evaluates the detection of low viral loads of SARS-CoV-2 by four multiplex molecular assays: Roche cobas 6800/8800 SARS-CoV-2 & Influenza A/B Test, Cepheid Xpert Xpress SARS-CoV-2/Flu/RSV, cobas Liat SARS-CoV-2 & Influenza A/B, and a laboratory-developed test (LDT). Retrospective upper respiratory tract specimens positive for various respiratory viruses at a range of cycle threshold (Ct) values (18-40) were tested by four multiplex assays. Positive and negative percent agreement (PPA and NPA) with validated RT-PCR assays were calculated. A total of 82 samples were assessed, with discordant results observed in a portion of the samples (10/82, 12.2%) where Ct values were >33. The majority of the discordant results (6/10, 60%) were false negatives. Overall, PPA was 100% (58/58) for cobas 6800, 97.4% (38/39) for GeneXpert, 100% (17/17) for Liat, and 90.5% (57/63) for the LDT. PPA for the LDT increased to 92.1% after manual review of amplification curves. Commercial multiplex respiratory virus assays have good performance for samples with medium to high viral loads (Ct values <33). Laboratories should consider appropriate test result review and confirmation protocols to optimize sensitivity, and may consider reporting samples with additional interpretive comments when low viral loads are detected.

Circulating Serotypes of Group A Rotavirus Identified in the Faeces of Children Aged 0-56 Months with Gastroenteritis

Gastroenteritis is a public health problem in developing countries such as Burkina Faso. The introduction of the RotaShield rotavirus vaccine in the early 1980s had the side-effect of causing acute intestinal invaginations, which led to the introduction of surveillance. The aim of this study is to review the serotypes of rotavirus identified. This retrospective study consisted in collecting data on group A rotavirus serotypes identified from stool samples using a rapid diagnostic test, confirmed by an ELISA test and then serotyped by real-time multiplex RT-PCR. A total of 840 suspect stools were collected between December 2013 and December 2017. Confirmed cases represented an average of 37.7%. Genotyping identified the P6(59.6%) and P8(40.4%) types of the P genotype in the VP4 genotype and G12 which predominates with 66% in the VP7 genotype followed by G3 23.4%. The genotypes most involved in gastroenteritis are serotypes P6 and P8 of the P genotype and serotypes G1, G2, G3, G9 and G12 of the G genotype in this study showed that.

TaqMan probe-based one-step multiplex real-time RT-PCR assay for the diagnosis of foot-and-mouth disease

Effective control and monitoring the spread of foot-and-mouth disease (FMD) relies upon rapid and accurate laboratory detection of FMD virus (FMDV). Therefore, in this report, a multiplex TaqMan probe-based one-step RT-qPCR assay simultaneously targeting FMDV 5′UTR and 3Dpol regions, and 18S rRNA housekeeping gene (as an internal control) in a single reaction tube was developed and evaluated. The multiplex one-step RT-qPCR assay specifically detected viral genome in both FMDV-infected cell culture suspensions and clinical samples collected from known-FMD infected animals. The assay could detect FMDV RNA in the archived FMDV cell culture isolates (n = 120) collected during the last two decades in India. In addition, the new assay could also detect viral RNA in the FMD suspected clinical samples (n = 740) collected from various field outbreaks. At a cut-off Ct-value of &amp;lt;38, the assay could detect at least 20 and 10 copies of FMDV 3Dpol and 5′UTR genes, respectively. Further, the multiplex RT-qPCR assay proved to be robust, showing an inter-assay co-efficient of variations ranging from 1.3% to 3.03% for FMDV-3Dpol gene target, and from 1.44% to 4.69% for 5′UTR gene target. In addition, it was found that the new assay could be used to detect viral genome in a variety of samples (epithelium, saliva, OPF, milk and blood) without any significance difference in the detection limit of the assay. Hence, the multiplex one-step RT-qPCR assay could be considered a valuable tool for the detection of FMDV in India.

External quality assessment for laboratories in pan-India ILI/SARI surveillance for simultaneous detection of influenza virus and SARS-CoV-2.

The Indian Council of Medical Research has set up a nationwide network of 28 laboratories for simultaneous surveillance of influenza virus and SARS-CoV-2 in ILI/SARI patients, using an in-house developed and validated multiplex real-time RTPCR assay. The aim of this study was to ensure the quality of testing by these laboratories by implementing an external quality assessment program (EQAP). For this EQAP, a proficiency test (PT) panel comprising tissue-culture or egg-grown influenza virus and SARS-CoV-2 was developed. The PT panel was distributed to all the participant laboratories, which tested the panel and submitted the qualitative results online to the EQAP provider. The performance of the laboratories was evaluated on qualitative criteria but cycle threshold (Ct) values were also gathered for each sample. On a qualitative basis, all the laboratories achieved the criteria of 90% concordance with the results of the PT panel provider. Ct values of different samples across the laboratories were within ≤ ±3 cycles of the corresponding mean values of the respective sample. The results of this EQAP affirmed the quality and reliability of testing being done for simultaneous surveillance of influenza virus and SARS-CoV-2 in India.

A multiplex real-time RT-PCR system to simultaneously diagnose 16 pathogens associated with swine respiratory disease.

Swine respiratory disease (SRD) is a major disease complex in pigs that causes severe economic losses. SRD is associated with several intrinsic and extrinsic factors such as host health status, viruses, bacteria, and environmental factors. Particularly, it is known that many pathogens are associated with SRD to date, but most of the test to detect those pathogens can be normally investigated only one pathogen while taking time and labor. Therefore, it is desirable to develop rapidly and efficiently detectable methods those pathogens to minimize the damage caused by SRD. We designed a multiplex real-time RT-PCR (RT-qPCR) system to diagnose simultaneously 16 pathogens, including nine viruses and seven bacteria associated with SRD, on the basis of single qPCR and RT-qPCR assays reported in previous studies. Multiplex RT-qPCR system we designed had the same ability to single RT-qPCR without significant differences in detection sensitivity for all target pathogens at minimum to maximum genomic levels. Moreover, the primers and probes used in this system had highly specificity because the sets had not been detected pathogens other than the target and its taxonomically related pathogens. Furthermore, our data demonstrated that this system would be useful to detect a causative pathogen in the diagnosis using oral fluid from healthy pigs and lung tissue from pigs with respiratory disorders collected in the field. The rapid detection of infected animals from the herd using our system will contribute to infection control and prompt treatment in the field.

Prevalence and Characterization of Gastroenteritis Viruses among Hospitalized Children during a Pilot Rotavirus Vaccine Introduction in Vietnam.

Rotavirus (RV), norovirus (NoV), sapovirus (SaV), and human astrovirus (HAstV) are the most common viral causes of gastroenteritis in children worldwide. From 2016 to 2021, we conducted a cross-sectional descriptive study to determine the prevalence of these viruses in hospitalized children under five years old in Nam Dinh and Thua Thien Hue provinces in Vietnam during the pilot introduction of the RV vaccine, Rotavin-M1 (POLYVAC, Hanoi, Vietnam). We randomly selected 2317/6718 (34%) acute diarrheal samples from children <5 years of age enrolled at seven sentinel hospitals from December 2016 to May 2021; this period included one year surveillance pre-vaccination from December 2016 to November 2017. An ELISA kit (Premier Rotaclone®, Meridian Bioscience, Inc., Cincinnati, OH, USA) was used to detect RV, and two multiplex real-time RT-PCR assays were used for the detection of NoV, SaV and HAstV. The prevalence of RV (single infection) was reduced from 41.6% to 22.7% (p < 0.0001) between pre- and post-vaccination periods, while the single NoV infection prevalence more than doubled from 8.8% to 21.8% (p < 0.0001). The SaV and HAstV prevalences slightly increased from 1.9% to 3.4% (p = 0.03) and 2.1% to 3.3% (p = 0.09), respectively, during the same period. Viral co-infections decreased from 7.2% to 6.0% (p = 0.24), mainly due to a reduction in RV infection. Among the genotypeable samples, NoV GII.4, SaV GI.1, and HAstV-1 were the dominant types, representing 57.3%, 32.1%, and 55.0% among the individual viral groups, respectively. As the prevalence of RV decreases following the national RV vaccine introduction in Vietnam, other viral pathogens account for a larger proportion of the remaining diarrhea burden and require continuing close monitoring.

Application of multiplex realtime PCR detection for hemorrhagic fever syndrome viruses

BackgroundMultiplex real-time PCR is a quick and cost effective method for detection of various gene simultaneously. HFSV (Hemorrhagic Fever Syndrome Virus) is a newly emerging infectious disease because of globalization and climate change. We tried to develop a molecular diagnostic technique for various causative viruses and evaluate its usefulness for improving public health. MethodsMolecular diagnostic test method that qualitatively detects viruses causing viral hemorrhagic fevers hired Taq-Man Real-time RT-PCR technique. The Ct value was experimentally observed three or more times at the RNA concentration before and after the detection limit. After designing a multiplex real-time RT-PCR test for target gene of selected 17 viruses, the detection limit for each target and the presence or absence of cross-reaction and interference reaction were evaluated to determine its availability. ResultsSix kinds of viruses, including Crimean-Congo hemorrhagic fever virus, Omsk hemorrhagic fever virus, Sabia virus, Chapare virus, Yellow fever virus, and Variola virus (A4L gene, B12R gene), were able to confirm the detection limit of 0.5 copies/μl, and other Ebola virus, Marburg virus, Rift Valley fever virus, Kyasanur Forest disease virus, Junin virus, Guanarito virus, Machupo virus, Chikungunya virus, Hantavirus, Dengue virus types 1–4, and Lassa virus (L gene, GPC gene), and 11 kinds of viruses, the detection limit was confirmed at 5 copies/μl. No cross-reaction or interference between detected genes was observed. ConclusionThe virus test method developed through this study using multiplex is expected to be used for public health and quarantine as a test method that can be used when a hemorrhagic fever virus of unknown cause is introduced.

Establishment and evaluation of a multiplex real-time RT-PCR for quantitative and differential detection of wild-type canine distemper virus from vaccine strains

This study sought to establish a real-time reverse transcription (RT)-PCR method to differentially detect canine distemper virus (CDV) wild-type and vaccine strains. To this end, a pair of CDV universal primers and two specific minor groove binder (MGB) probes, harboring a T/C substitution in the hemagglutinin (H) gene, were designed. Using a recombinant plasmid expressing the H gene of the CDV wild-type or vaccine strain as standards, a sensitive and specific multiplex real-time RT-PCR was established for quantitative and differential detection of CDV wild-type and vaccine strains. The limit of detection for this multiplex assay was 22.5 copies/μL and 2.98 copies/μL of viral RNA for wild-type and vaccine strains, respectively. Importantly, the wild-type and vaccine MGB probes specifically hybridized different genotypes of wild-type CDV circulating in China as well as globally administered vaccine viruses, respectively, with no cross-reactivity observed with non-CDV viruses. Moreover, this method was successfully applied for the quantitative detection of CDV RNA in tissue samples of experimentally infected breeding foxes, raccoon dogs, and minks. Additionally, the multiplex real-time RT-PCR was able to detect the viral RNA in the whole blood samples as early as 3 days post-infection, 3 to 4 days prior to the onset of clinical signs in these CDV infection animals. Hence, the established multiplex real-time RT-PCR method is useful for differentiating wild-type CDV and vaccine strains in China, and for conducting canine distemper early diagnosis as well as dynamic mechanism of CDV replication studies in vivo.

A COMPARATIVE STUDY OF RAPID SARS COV 2 ANTIGEN DETECTION TEST &amp; REAL TIME PCR TEST FOR DIAGNOSIS OF COVID-19 IN TERTIARY CARE INSTITUTE AT KOTA, SOUTH-EAST RAJASTHAN, INDIA

Background:The 2019 (Covid19) pandemic of coronavirus disease was caused by SARS Cov 2 Virus. The emergence of the disease was started from the Wuhan city of China in December 20191. This infection causes asymptomatic and mild diseases more than severe pneumonia. A Rapid Lateral flow immunoassays using monoclonal anti-SARS CoV- 2 antibodies, targeting SARS-CoV-2 antigens, can be used as complementary screening tests if their accuracy comes comparable to that of gold standard real-time RT-PCR assays. Objective:The present study has been conducted retrospectively on the data of patients who underwent for Covid 19 diagnosis by RAT at the Microbiology Department Central Laboratory, Maharao Bhim Singh Hospital Nayapura Kota. Material and Method: Respiratory samples from suspected 5219 COVID-19 patients, mainly nasopharyngeal and throat swabs were collected. COVID-19 Ag Confirmit™ kit (Alpine biomedicals) is a rapidchromatographic immunoassay for the detection ofSARS-CoV-2 nucleoprotein (N) antigen in respiratoryspecimens. Multiplex Real-time RT-PCR kit (TRIVITRON healthcare) was used, whichtargets envelope gene (E), and Orf1ab gene of SARS-CoV-2 genome and RPP30 Human gene as internal control, was used for SARS-CoV-2RNA detection. Descriptive statistics were used to describe the usefulness of rapid diagnostic tests. For that online MedCalcs Diagnostic test evaluation statistical tool10. Result: Among all 5219 samples (n=5219) tested by RT-PCR 785 (15.4%) samples were positive and 4434 (84.95%) were negative. Samples tested by RAT 813 (15.57%) samples were positive &amp; 4406 (84.42%) were negative, in our study we found discordant results in 36 samples. The sensitivity and specificity of the COVID-19 Ag Confirmit™ kit (Alpine biomedicals) were 99.49% and 99.28% respectively. Discussion: Out of 785 RT-PCR-positive samples in our study, the 4 false negative results were tested for SARS-CoV-2 antigen seven days after disease onset. The RT-PCR result of these samples had relatively high Ct-values. Without the present population prevalence of COVID-19, the positive and negative predictive values (PPV and NPV) of the assay could not be accurately calculated. Conclusions: There is comparable Sensitivity and Specificity between Rapid assay for SARS-CoV-2 antigen detection (COVID-19 Ag Confirmit™ kit) and real-time RT-PCR assay.

Norovirus gastroenteritis in children under-five years hospitalized for diarrhea in two cities of northeast India: A retrospective study

PurposeNorovirus gastroenteritis, known to cause ‘winter vomiting disease’ is increasingly being identified as a major cause of viral gastroenteritis worldwide. The impact and prevalence of this viral disease are lacking in many parts of India including northeast India. This study aimed to determine the prevalence and association of norovirus gastroenteritis among under-five-year-old hospitalized children in two cities in northeast India (Dibrugarh in Assam & Dimapur in Nagaland). Materials and methodsA retrospective analysis of 407 randomly selected diarrheal stool samples was conducted using a commercial multiplex probed-based real-time RT-PCR assay capable of detecting six-viral gastroenteritis pathogens including Norovirus GI, Norovirus GII, Rotavirus, Human Adenovirus, Human Astrovirus, and Sapovirus. ResultsResults showed that norovirus was detected in 18.4% of the samples (75/407; 95% CI: 14.8%–22.5%), with norovirus genogroup II being the predominant group in 97.3% of norovirus cases. A significant association of norovirus diarrhea was found with seasonality, with higher prevalence in colder months compared to warmer months (22.4% vs 9.1%, p-value:0.002). Additionally, 66.7% (50/75) of cases of norovirus gastroenteritis had reported vomiting as the major symptom and had a shorter duration of diarrhea (p-value 0.03). Co-infections with other viral pathogens were seen in 45.9% (187/407) of the cases. The detection of rotavirus was 67.1% (273/407), human adenovirus (45.9%; 187/407), sapovirus and astrovirus (5.9%, 24/407 each), and norovirus GI (0.5%, 2/407) among the cases. ConclusionThis study reports the prevalence of norovirus gastroenteritis in northeast India and further highlights that norovirus gastroenteritis is responsible for substantial cases of hospitalization of under-five years children in the region.

TaqMan Multiplex Real-time PCR Assay for Crimean-Congo Hemorrhagic Fever Virus Diagnosis Using Armored RNA Technology

Background: Crimean-Congo hemorrhagic fever virus (CCHFV) is a highly lethal virus that causes hemorrhagic fever in humans and is endemic in many countries, including Iran. Therefore, fast, accurate, and reliable diagnosis is crucial for patient management and outbreak control. Objectives: This study aims to optimize a TaqMan multiplex real-time RT-PCR for the rapid and specific diagnosis of CCHFV. Methods: In this study, the L (NC_005301.3) and S (NC_005302.1) fragments were used as reference sequences for blast analysis. The L and S sequence segments of CCHFV with more than 90% identity from different areas were downloaded from the Genbank database. Primers and probes were designed based on the best-conserved regions of CCHFV L and S sequence segments. To construct the plasmid, a 1751 bp fragment from the MS2 phage that was previously amplified using cloning primers was inserted into the pET-32a plasmid. The S and L segments of the CCHFV, which were 110 bp and 135 bp, respectively, were inserted downstream of the MS2 phage sequence from HindIII to NotI. The Viral-like particles (VLPs) were produced in Escherichia coli, strain BL-21(DE3), in the presence of 1 mM Isopropyl β-D-1-thiogalactopyranoside (IPTG). The stability of VLP particles was confirmed in the presence of the ribonuclease enzyme. The fabrication of VLPs was approved by transmission electron microscopy (TEM) with negative staining (1% phosphotungstic acid). To validate the specificity of the primers and probes sequences, we compared them to the NCBI database and tested them experimentally using extracted DNA and RNA samples from healthy subjects and an infectious panel. Results: The VLPs showed complete resistance in the presence of the ribonuclease enzyme, and the TEM results confirmed that the VLPs were correctly produced. The TaqMan multiplex real-time RT-PCR confirmed that the primers and probes were designed correctly and were completely specific to the CCHFV. The limit of detection (LOD) of the multiplex assay for the L and S genes was one copy of the VLPs per µL. Conclusions: This TaqMan assay is reliable for amplifying CCHFV due to its design on conserved regions of the CCHFV sequences, which have minimal variability and high specificity.