Rapid Assay Research Articles

Portable detection of Salmonella in food of animal origin via Cas12a-RAA combined with an LFS/PGM dual-signaling readout biosensor.

Ahighly specific and sensitive rapid two-signal assay was developedfor the detection of Salmonella typhimurium in foods of animal origin. TheinvA gene of Salmonella was usedas the biorecognition element and recombinase-assisted amplification (RAA) technology for signal amplification. By utilizing the specific recognition and efficient trans-cleavage activity of CRISPR/Cas12a, point-of-care testing (POCT) for S. typhimurium was achieved via lateral flow strips (LFS) and personal glucometer (PGM) biosensors as dual signal readout systems, with sensitivities of 33CFU/mL and 20CFU/mL, respectively. Users can select the appropriate test system on the basis of specific application requirements: LFSs are ideal for rapid onsite screening, whereas glucometer biosensors offer precise quantitative determination. This approach simplifies the use of large instruments and overcomes site constraints, demonstrating good accuracy and applicability in animal-derived samples, with significant potential for the detection of other pathogens and for use in restricted environments.

Molecular characterization of ‘Candidatus Phytoplasma australasiaticum’ associated with ornamentals, amaranthus, French bean and sunhemp crops and development of rapid LAMP assay for detection

Phytoplasma is one of the most economically important pathogens, causing significant yield losses in many crops worldwide. During a survey in Bengaluru rural and Chikkabalpura areas of Karnataka, India, a total of 33 symptomatic plant samples including ornamentals, amaranthus, french bean, and sunhemp displaying phytoplasma symptoms were collected and confirmed as infected with phytoplasma through PCR targeting the 16S rRNA and secY genes. Pairwise sequence comparison and phylogenetic analysis of 16S rRNA and secY gene sequences confirmed the presence of ‘Candidatus Phytoplasma australasiaticum’ in antirrhinum, chrysanthemum, china aster, dianthus, amaranthus, french bean, and sunhemp. In-silico restriction fragment length polymorphism (RFLP) analysis indicated that phytoplasma strains infecting Antirrhinum, China aster, Dianthus, French bean, and Sunhemp represented distinct variants within the 16SrII phytoplasma group, with a threshold similarity coefficient of less than 0.98. A loop-mediated isothermal amplification (LAMP) assay was developed for detecting phytoplasma strains infecting the four ornamentals and other studied crops, targeting the phytoplasma 16S rRNA gene sequence with detection in 60 min. The comparative testing of LAMP products using various nucleic acid dyes and a colorimetric dye (hydroxy naphthol blue) confirmed the presence of phytoplasmas in symptomatic samples. This LAMP assay offers superior ease of use, cost-effectiveness, and rapid results for detecting phytoplasmas in symptomatic plants.

Evaluation of the Eazyplex®Candida ID LAMP Assay for the Rapid Diagnosis of Positive Blood Cultures.

Rapid molecular assays can be used to identify Candida pathogens directly from positive blood cultures (BCs) in a timely manner compared to standard methods using subcultures. In this study, the eazyplex®Candida ID assay, which is based on loop-mediated amplification (LAMP) and is currently for research use only, was evaluated for the identification of the most common fungal species. A total of 190 BCs were analysed. Sensitivity and specificity were 93.88% and 99.26% for C. albicans, 89.13% and 100% for Nakaseomyces glabratus (N. glabratus), 100% and 100% for Pichia kudravzevii (P. kudriavzevii), 100% and 100% for C. tropicalis, and 100% and 99.44% for C. parapsilosis. Sample preparation took approximately 11 min and positive amplification results were obtained between 8.5 and 19 min. The eazyplex®Candida ID LAMP assay is an easy-to-use diagnostic tool that can optimise the management of patients with candidemia.

Diagnostic Performance of Unstimulated IFN-γ (IRISA-TB) for Pleural Tuberculosis: A Prospective Study in South Africa and India.

Tuberculous pleural effusion (TPE) is the most common form of extrapulmonary tuberculosis in many settings. The diagnostic performance of the frontline polymerase chain reaction-based GeneXpert MTB/RIF Ultra (Xpert Ultra) remains suboptimal (sensitivity of ∼30%), but data are limited. Improved diagnostic approaches are urgently needed to detect extrapulmonary tuberculosis (EPTB) in tuberculosis (TB)-endemic settings. This multicenter, prospective cohort study evaluated the diagnostic performance of a rapid (same-day) interferon gamma rapid immunosuspension assay (IRISA-TB) in patients with presumed TPE from South Africa and India. Participants underwent pleural biopsy, and testing with other available same-day diagnostic assays (adenosine deaminase [ADA], Xpert Ultra, and IRISA-TB) was concurrently undertaken. The reference standard for TB was microbiological and/or histopathological confirmation using pleural fluid and/or pleural biopsy samples. A total of 217 participants with presumed TPE were recruited (106 from South Africa, 111 from India). The sensitivity of IRISA-TB (cut-point 20.5 pg/mL) was significantly better than that of Xpert Ultra (81.8% [70.4-90.2] vs 32.9% [22.1-45.1]; P < .001) and ADA at the 40 IU/mL cut-point used in India (81.8% [70.4-90.2] vs 53.8% [41.0-66.3]; P = .002). Compared with ADA at the 30 IU/mL cut-point used in South Africa, IRISA-TB had a higher specificity (96.6% [90.3-99.3] vs 87.1% [78.6-93.2]) and a higher positive predictive value (94.7% [85.5-97.3] vs 81.8% [72.4-88.5]). The negative predictive value (NPV; rule-out value) of IRISA-TB was significantly better than that of Xpert Ultra (87.5% [83.2-93.0] vs 64.9% [61.1-68.6]; P < .001) and ADA at the 40 IU/mL cut-point (87.5% [83.2-93.0] vs 74.1% [68.7-79.0]; P < .001). IRISA-TB demonstrated markedly better sensitivity and NPV than Xpert Ultra and excellent specificity for the diagnosis of TPE. These data have implications for clinical practice in TB-endemic settings.

A novel, simple and rapid assay to measure citrate level in bacterial culture for analysis of citrate consumption by bacteria

Citrate is essential for Krebs cycle in eukaryotes and serves as a carbon source for some bacteria to survive/grow. Available methods for measuring citrate level rely mainly on enzymatic reactions and/or sophisticated instrumentations. This study aimed to develop a novel, simple and rapid assay to quantify citrate in bacterial culture for analysis of citrate consumption. The assay was initially tested with 0.1–25.6 mM citrate in deionized (dI) water or complete M9 medium without/with 0.25 M HCl. Wavelength scan revealed maximum absorption of citrate at λ210 nm with linear calibration curve (R2 = 0.9997–0.9999) when HCl was added. Among negatively charged chemicals tested, only oxalate interfered with the assay. After 24-h inoculation of Klebsiella pneumoniae (the known citrate-utilizing bacterium) in (20 mM) citrate-containing complete M9 medium, the remaining citrate significantly decreased (by 22.20±7.13 % consumption). However, a mild decrease was also observed in the sample without bacterial inoculation, suggesting that some components of the complete medium interfered with the assay. It was clearly evidenced that M9 salt, CaCl2 and/or MgSO4 were responsible for such interference. Finally, citrate at low concentrations (0.1–6.4 mM) in M9 medium with CaCl2 and/or MgSO4 provided the linear calibration curve (R2 = 0.9451–0.9986). At 5 mM, citrate consumption by K. pneumoniae after 24-h culture was 46.88±0.47 %. In summary, we have successfully developed a novel, simple and rapid method for measuring citrate level in bacterial culture. It will be very useful for measuring citrate consumption by typical and atypical citrate-utilizing bacteria for classification, mechanistic and pathophysiologic studies.

A method for the quantitative analysis of Lycium barbarum polysaccharides (LBPs) using Fourier-transform infrared spectroscopy (FTIR): From theoretical computation to experimental application

Lycium barbarum polysaccharides (LBPs) is one of the most important active substances in Lycium barbarum (LB). It is a challenge to quantitatively determine the content due to their complex structures and lack of suitable reference standard in practice. In this study, a quantitative analysis method of LBPs in LB was established based on Fourier-transform infrared spectroscopy (FTIR). The stretching vibration of CO on the pyranose ring of saccharide at 921 cm−1 was selected as the characteristic absorption band by theoretical calculation, which can’t be impacted by the preparation methods and interfered by the component monosaccharides. The molecular weight CRM of dextran (Mw 63.3 kDa) served as the reference standard. The introducing internal standard (KSCN) can obtain a good precision (RSD = 1.10 %) and effectively compensate for the analysis errors caused by the environment, quality loss and uneven distribution during the tablet pressing processes. The methodological verification suggested that the method had good accuracy according to the recovery rate (96.61 %–105.45 %) and the blank recovery (92.39 %–99.37 %), respectively. The LOD and LOQ of CRMD were 0.10 mg and 0.32 mg, respectively. The polysaccharide content of LB from 24 different regions (0.50–2.54 %) and 10 batches of LB extracts (7.09–10.56 %) determined by the developed method less than the ones using phenol–sulfuric acid assay (1.95 %–4.83 % for LB and 9.83–15.53 % for extracts, respectively). The established method based on FTIR could be served as a supplement to phenol–sulfuric acid assay and a rapid quantitative assay for polysaccharides products. In additional, this study provided a new idea for the quantitative analysis of plant polysaccharides.

Development and Validation of the MAST ISOPLEX®VTEC Kit for Simultaneous Detection of Shiga Toxin/Verotoxin 1 and 2 (stx1/vt1 and stx2/vt2) with Inhibition Control (IC) in a Rapid Loop-Mediated Isothermal Amplification (LAMP) Multiplex Assay.

Loop-mediated isothermal amplification (LAMP) is a cost-effective, rapid, and highly specific method of replicating nucleic acids. Adding multiple targets into a single LAMP assay to create a multiplex format is highly desirable for clinical applications but has been challenging due to a need to develop specific detection techniques and strict primer design criteria. This study describes the evaluation of a rapid triplex LAMP assay, MAST ISOPLEX®VTEC, for the simultaneous detection of Shiga toxin/verotoxin 1 and 2 (stx1/vt1 and stx2/vt2) genes in verotoxigenic Escherichia coli (E. coli) (VTEC) isolates with inhibition control (IC) synthetic DNA using a single fluorophore-oligonucleotide probe, MAST ISOPLEX®Probes, integrated into the primer set of each target. MAST ISOPLEX®Probes used in the MAST ISOPLEX®VTEC kit produce fluorescent signals as they integrate with reaction products specific to each target, allowing tracking of multiple amplifications in real time using a real-time analyzer. Initial validation on DNA extracts from fecal cultures and synthetic DNA sequences (gBlocks) showed that the MAST ISOPLEX®VTEC kit provides a method for sensitive simultaneous triplex detection in a single assay with a limit of detection (LOD) of less than 100 target copies/assay and 96% and 100% sensitivity and specificity, respectively.

Homemade isothermal amplification-initiated Cas14a assay for rapid quantitative detection of aquatic RNA virus gene with no PAM

The red-spotted grouper nervous necrosis virus (RGNNV) is the most widely distributed nervous necrosis virus (NNV) and causes a significant risk to aquatic food safety. Though a few CRISPR-based aquatic pathogen detection methods have been reported recently, the absence of the PAM site of RGNNV specific gene RNA2 impedes its CRISPR-based diagnostic. Herein, we developed a rapid and accurate homemade isothermal amplification-initiated Cas14a assay (HiaCas14a) for RGNNV detection. The introduction of the PAM site into RT-LAMP specific amplicons of RGNNV RNA2 unlocked its PAM restriction. Furthermore, fish genomic RNA purified by magnetic beads and polymerases used in RT-LAMP prepared by ourselves obviously gave the system an enhanced convenience and a reduced cost. HiaCas14a detected 63.4 aM RNA with excellent specificity and sensitivity quantitatively, and it demonstrated a high accuracy of field sample validation results compared with RT-qPCR. The method provided an accurate, low-cost, and sensitive tool for aquatic pathogen detection in resource-poor areas.

Abstract B054: Protease activity as a biomarker and potential target among pancreatic cancer patients

Abstract Background: The pancreas produces digestive proteases, which are often elevated in diseased states and capable of indiscriminate cell surface receptor cleavage. High levels of digestive protease activity have been implicated in the pathophysiology of pancreatic ductal adenocarcinoma (PDAC). We hypothesize that elevated digestive protease activity might downregulate or cleave immune cell receptors from the surface of cancer cells and contribute to the resistance of PDAC to immunotherapy. We have focused initially on major histocompatibility complex (MHC)-1, a ubiquitous receptor essential for antigen presentation, and CD155, an adhesion molecule over-expressed on cancer cells that regulates immune surveillance through binding to the TIGIT and CD226 receptors on leukocytes. Methods: The Rapid Assay for Protease Detection (RAPD) assay is a novel assay developed at our institution that utilizes fluorescent charge-changing peptide substrates to produce a positively charged fluorescent product fragment upon cleavage by the target protease. The RAPD assay was used to analyze protease activity levels in PDAC patients (N=50) and healthy (N=25) plasma samples. We also analyzed plasma samples obtained from an orthotopic KPC-derived mouse model for PDAC. We investigated the effects of specific proteases as well as plasma samples from PDAC and healthy subjects on MHC-1 and CD-155 receptor cleavage in cultured cells in vitro. Utilizing flow cytometry and immunofluorescent imaging, receptor loss was quantified for different proteases and plasma samples. Results: We observed elevated activity levels of digestive protease chymotrypsin as well as cathepsin-S and MMP-2 in the plasma of PDAC patients compared to healthy subjects. Similar patterns of protease activity were seen in plasma from tumor-bearing mice compared to non-tumor-bearing mice. Additionally, our results suggest loss of CD155 and MHC-1 from pancreatic cancer cells when incubated with trypsin and cathepsin-S. Incubation of cells with PDAC plasma also decreases the number of cells expressing MHC-1 and CD155 compared to control plasma, with greater differences observed in plasma with higher protease levels. Higher levels of cleaved CD155 are also detectable by ELISA in human and mouse PDAC plasma than in control plasma. Also, the protease activity (MMP2 and trypsin) correlates with plasma levels of CD155 and PD-L1. Conclusions: These studies begin to elucidate a possible role of digestive proteases in the ability of PDAC to evade the immune system. Ongoing experiments are exploring other immune receptors (including checkpoints) and whether specific protease inhibitors can block immune receptor cleavage. These experiments will inform subsequent experiments combining protease inhibitors with immunotherapy in mouse models. Citation Format: Utsav Joshi, Heather Farris, Jorge De La Torre De La Torre, kim Nguyen-Ta1, Michael Heller, Geert Schmid-Schonbein, Rebekah White. Protease activity as a biomarker and potential target among pancreatic cancer patients [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research; 2024 Sep 15-18; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(17 Suppl_2):Abstract nr B054.

Evaluation of cobas® Liat® Cdiff, STANDARD™ M10 C. difficile and Xpert® C. difficile BT assays for rapid detection of toxigenic Clostridioides difficile

We evaluated the analytical performance of three commercial molecular assays for rapid detection of Clostridioides difficile toxin B in stool samples. The results were compared with results from the BD MAX™ Cdiff assay. We analyzed forty negative and thirty-two positive stool samples with three rapid assays: Roche cobas® Liat® Cdiff, SD Biosensor STANDARD™ M10 C. difficile and Cepheid Xpert® C. difficile BT. The assays demonstrated a sensitivity of 96.9 %, 96.9 % and 100.0 % and a specificity of 100 %, 97.5 % and 97.5 %, respectively. There is limited data available on the analytical performance of the newly introduced STANDARD™ M10 C. difficile assay. In this study, all three rapid assays demonstrated similarly high analytical performance and can be used for detection of toxigenic C. difficile.

Rapid Tryptophan Assay as a Screening Procedure for Quality Protein Maize.

Tryptophan is an essential amino acid deficient in cereals, especially maize. However, maize (Zea mays L.) is the main source of protein in some developing countries in Africa and Latin America. In general, the nutritional profile of cereals is poor, because they are deficient in essential amino acids such as tryptophan and lysine due to a relatively higher proportion of alcohol-soluble proteins. Quality protein maize (QPM) has been developed through genetic manipulation for the nutritional enrichment of maize to address these problems. Nevertheless, methods for protein, lysine and tryptophan are time-consuming and require relatively large amounts of samples. Therefore, we have advanced here a simple, cheap, fast, reliable and robust procedure for the determination of protein and tryptophan in the same biuret supernatant, which can also be used for chemical characterization of other cereals. Samples of 50 mg maize ground to pass through a 0.1 mm screen were sonicated for 5 min. in eppendorf vials with 1.5 mL of a biuret reagent each. After centrifugation and protein determination by biuret, 0.2 mL of supernatant was treated with 0.8 mL of a tryptophan reagent. Both total protein and tryptophan can be determined in microplates at 560 nm to speed up the measurements. The main advantage of the new micro-method is the rapid estimation of the nutrient quality of maize samples by a single weighing of a small amount of valuable plant materials.

Rapid Fluorescence Assay for Polyphosphate in Yeast Extracts Using JC-D7.

Polyphosphate (polyP) is an intriguing molecule that is found in almost any organism, covering a multitude of cellular functions. In industry, polyP is used due to its unique physiochemical properties, including pH buffering, water binding, and bacteriostatic activities. Despite the importance of polyP, its analytics is still challenging, with the gold standard being 31P NMR. Here, we present a simple staining method using the fluorescent dye JC-D7 for the semi-quantitative polyP evaluation in yeast extracts. Notably, fluorescence response was affected by polyP concentration and polymer chain length in the 0.5-500 µg/mL polyP concentration range. Hence, for polyP samples of unknown chain compositions, JC-D7 cannot be used for absolute quantification. Fluorescence of JC-D7 was unaffected by inorganic phosphate up to 50 mM. Trace elements (FeSO4 > CuSO4 > CoCl2 > ZnSO4) and toxic mineral salts (PbNO3 and HgCl2) diminished polyP-induced JC-D7 fluorescence, affecting its applicability to samples containing polyP-metal complexes. The fluorescence was only marginally affected by other parameters, such as pH and temperature. After validation, this simple assay was used to elucidate the degree of polyP production by yeast strains carrying gene deletions in (poly)phosphate homeostasis. The results suggest that staining with JC-D7 provides a robust and sensitive method for detecting polyP in yeast extracts and likely in extracts of other microbes. The simplicity of the assay enables high-throughput screening of microbes to fully elucidate and potentially enhance biotechnological polyP production, ultimately contributing to a sustainable phosphorus utilization.

Correlates of Hepatitis B infection in pregnant women attending antenatal clinics in Wa Municipality, Ghana.

Despite the availability of an effective vaccine against viral hepatitis B infection, it remains prevalent, highly transmissible especially through mother-to-child, life-threatening, and a major public health challenge. A positive Hepatitis B e-Antigen (HBeAg) mother has a 90% risk of transmitting the virus to the unborn child in the perinatal period. This study sought to determine the prevalence and risk of Hepatitis B infection among pregnant women in the Wa Municipality of Ghana. A cross-sectional study employing systematic random sampling was conducted among 183 consented pregnant women who went for antenatal care in nine health facilities in the Wa Municipality. A structured validated questionnaire was used to collect information about socio-demographic and obstetric characteristics, awareness of Hepatitis B Virus (HBV) transmission and its prevention. Blood samples (3.0 mls) were collected from each participant to test for HBV serum markers using a Wondfo One Step HBV rapid immunochromatographic assay (Catalog number W003) for the Hepatitis B surface antigen (HBsAg). We conducted descriptive statistics including the prevalence and used multivariable logistic regression to determine the risk of Hepatitis B among study participants. Data was analysed using Stata/SE 15. About 20.2% of the 183 pregnant women screened tested positive for HBsAg. Generally, compared with younger pregnant women, older (> = 25) pregnant women were >9 times less likely to test positive for both chronic Hepatitis B core antibody (HBcAb) and (HBeAg) Hepatitis B infections. However, pregnant women in polygamous relationship were more likely to test positive for both (HBcAb) and (HBsAg and HBeAg) Hepatitis B infections compared with those in monogamous relationship. In a multivariable analysis, pregnant women in a polygamous relationships were about 5 times more likely to test positive for HBsAg (AOR = 4.61, 95% CI: 2.06-9.89) and HBcAb (AOR = 4.89, 95% CI:1.52-6.81) and HBeAg (AOR = 4.62, 95% CI:1.21-6.39) compared with those in a monogamous relationship. This study highlights a high HBsAg prevalence among pregnant women with those in polygamous relationship and younger age more likely to test positive. Facility and community-based health services should emphasize the need for regular screening, education, and vaccination of pregnant women, especially those at high risk, to prevent mother-to-child transmission of viral hepatitis B.

Synergistic Role of the AuAg-Fe3O4 Nanoenzyme for Ultrasensitive Immunoassay of Dengue Virus.

A combination of magnetic and noble metal nanoparticles (NPs) has recently emerged as a potential substance for rapid and sensitive immunosorbent assays. However, to make the assay an alternative method for Enzyme-linked immunosorbent assay, the individual role of each nanoparticle must be explored properly. In this work, an immunoassay has been proposed using two antibody-conjugated iron oxide nanoparticles (Fe3O4NPs) and gold-silver bimetallic nanoparticles (AuAgNPs) to enhance the sensitivity of virus detection by colorimetric TMB/H2O2 signal amplification. A synergistic effect is monitored between Fe3O4NPs and AuAgNPs, which is explored for colorimetric virus detection. The sensor exploits the synergistic effect between the nanoparticles to successfully detect a wide range of dengue virus-like particle (DENV-LP) concentrations ranging from 10 to 100 pg/mL with a detection limit of up to 2.6 fg/mL. In the presence of a target DENV-LP, a sandwich-like structure is formed, which restricts the electron transfer and the associated synergistic effect between the nanoparticles, restricting the TMB oxidation process. Therefore, the synergistic effect is the key to the present work, which accounts for the enhanced rate of the enzymatic reaction on TMB and makes the current method of virus detection more sensitive and reliable compared to the others.

Efficient Absorbance-Based Assay for Rapid Antibiotic Susceptibility Testing of Enterobacterales.

It is increasingly important to rapidly receive information on the antimicrobial susceptibility of bacteria due to the rise in antimicrobial resistance worldwide. However, traditional phenotypic methods are time-consuming. Thus, the objective of this study was to develop a rapid assay that can detect antibiotic-resistant bacterial isolates phenotypically in less than 2 h. The microplate assay used in this study is based on absorbance measurements of pure bacterial isolates grown in liquid media with and without antibiotics. Absorbance was measured at the beginning of the assay and after 90 min of incubation at 37 °C. Susceptibility was calculated for bacterial isolates that, in the absence of antibiotics, exhibited more than a 50% growth increase by comparing the absorbance value of the culture in the presence of an antibiotic at 90 min with its initial value. Here, we show that it is possible to phenotypically screen the antibiotic susceptibility of Enterobacterales and Acinetobacter spp. isolates to three different antibiotics in 90 min. The test demonstrated an accuracy of 98.8%, sensitivity of 97.6%, and specificity of 99.6%. The false susceptibility rates were 0.2% and false resistance rates were 1.0%. This rapid and simple absorbance test has proven suitable for the screening of antibiotic susceptibility for a large number of strains with high accuracy and sensitivity. This method can be performed without specialized and costly materials and/or equipment, which makes it highly suitable for laboratories with limited resources.

ƩS COVID-19 is a rapid high throughput and sensitive one-step quadruplex real-time RT-PCR assay

Real-time reverse transcription polymerase chain reaction (RT-PCR), a standard method recommended for the diagnosis of coronavirus disease 2019 (COVID-19) requires 2–4 h to get the result. Although antigen test kit (ATK) is used for COVID-19 screening within 15–30 min, the drawback is its limited sensitivity. Hence, a rapid one-step quadruplex real-time RT-PCR assay: termed ƩS COVID-19 targeting ORF1ab, ORF3a, and N genes of SARS-CoV-2; and Avocado sunblotch viroid (ASBVd) as an internal control was developed. Based on strategies including designing high melting temperature primers with short amplicons, applying a fast ramp rate, minimizing hold time, and reducing the range between denaturation and annealing/extension temperatures; the assay could be accomplished within 25 min. The limit of detection of ORF1ab, ORF3a, and N genes were 1.835, 1.310, and 1 copy/reaction, respectively. Validation was performed in 205 combined nasopharyngeal and oropharyngeal swabs. The sensitivity, specificity, positive predictive value, and negative predictive value were 92.8%, 100%, 100%, and 97.1%, respectively with 96.7% accuracy. Cohen’s Kappa was 0.93. The newly developed rapid real-time RT-PCR assay was highly sensitive, specific, and fast, making it suitable for use as an alternative method to support laboratory diagnosis of COVID-19 in outpatient and emergency departments.

Clinical performance of a rapid RT-PCR assay using STANDARD™ M10 SARS-CoV-2 between July 2022 and January 2023 in Korea

Rapid detection of SARS-CoV-2 is essential for clinical management in the emergency department during the COVID-19 pandemic. We evaluated the clinical performance of the recently developed cartridge-based rapid RT-PCR assay (STANDARD M10 SARS-CoV-2) in patients visiting the emergency department from July 2022 to January 2023, which was when the Omicron BA.5 sublineage was predominant in Korea. A total of 534 specimens were subjected to the STANDARD M10 and standard RT-PCR (Allplex SARS-CoV-2) assays. The overall, positive, and negative percent agreements between these two assays were 99.6%, 100%, and 99.6%, respectively. The results showed that compared with the established RT-PCR assay, the STANDARD M10 SARS-CoV-2 assay is a reliable and useful tool for SARS-CoV-2 detection during the study period. The new rapid RT-PCR will expand the diversity in rapid diagnostics and can help resolve the global imbalance associated with the supply of diagnostic resources.

Point-of-care urine tenofovir test predicts future HIV preexposure prophylaxis discontinuation among young users.

Young men who have sex with men and transgender women (YMSM/TGW) have disproportionately high HIV incidence and lower preexposure prophylaxis (PrEP) adherence. Point-of-care (POC) urine tenofovir (TFV) rapid assay (UTRA) testing permits real-time monitoring for nonadherence within clinical settings. We performed UTRA testing among PrEP users to examine the relationship between low PrEP adherence and future PrEP discontinuation, and the accuracy of POC testing compared to gold-standard liquid chromatography tandem mass spectrometry (LC/MS/MS). YMSM/TGW participants ( n = 100) were recruited during a daily PrEP visit. Logistic regression models analyzed the relationship between the primary predictor of urine POC assay results (cutoff 1,500 ng/ml) and the primary outcome of PrEP discontinuation, defined as no PrEP follow-up or prescription within 120 days. Overall, 19% of participants had low urine TFV and 21% discontinued PrEP, while 11% of participants self-reported low PrEP adherence (<4 pills per week), which was only 43% sensitive/84% specific in predicting low TFV levels and was not associated with PrEP discontinuation. Low urine TFV level predicted PrEP discontinuation [adjusted odds ratio (AOR) 6.1; 95% confidence interval (CI): 1.4-11; P = 0.005] and was 71% sensitive/90% specific for discontinuation after 120 days. Compared to LC/MS/MS, UTRA testing had a 98% positive and 100% negative predictive value. In a sample of YMSM/TGW on daily PrEP, POC UTRA testing predicted PrEP discontinuation more accurately than self-reported adherence, with high predictive values compared to LC/MS/MS. UTRA testing may be a clinical tool for directing preventive interventions towards those likelier to discontinue PrEP despite ongoing HIV vulnerability.

Loop-Mediated Isothermal Amplification Assay to Detect Invasive Malaria Vector Anopheles stephensi Mosquitoes.

Spread of the Anopheles stephensi mosquito, an invasive malaria vector, threatens to put an additional 126 million persons per year in Africa at risk for malaria. To accelerate the early detection and rapid response to this mosquito species, confirming its presence and geographic extent is critical. However, existing molecular species assays require specialized laboratory equipment, interpretation, and sequencing confirmation. We developed and optimized a colorimetric rapid loop-mediated isothermal amplification assay for molecular An. stephensi species identification. The assay requires only a heat source and reagents and can be used with or without DNA extraction, resulting in positive color change in 30-35 minutes. We validated the assay against existing PCR techniques and found 100% specificity and analytical sensitivity down to 0.0003 ng of genomic DNA. The assay can successfully amplify single mosquito legs. Initial testing on samples from Marsabit, Kenya, illustrate its potential as an early vector detection and malaria mitigation tool.

Evaluation of a commercial Immunochromatographic Strip Assay (ICT) for rapid detection of bovine, porcine and human Rotavirus A

The most frequent diarrhoeal pathogen “Rotavirus” is commonly detected by Ribo Nucleic Acid- Polyacrylamide Gel Electrophoresis (RNA-PAGE), Reverse Transcription Polymerase Chain Reaction (RT-PCR) and Immunoassay (Enzyme Linked Immunosorbent Assay) in humans. However, use of these tests is limited in animals therefore, penside test like Immunochromatographic test/Lateral Flow Assay (ICT/LFA) is necessary. The present study was carried out to compare the diagnostic efficacy of rapid commercial ICT strip assay, RNA-PAGE and RT-PCR for specific detection of Rotavirus A (RVA) from stool samples of calves, piglets and children. A total of 313 faecal samples were collected between November 2022 to April 2023 from children below 5years of age (n=100), calves (n=100) and piglets (n=113) ≤ 3 months of age and were screened by RNA-PAGE, RT-PCR and commercial ICT kit for rotavirus A.The overall positivity of RVA from human, calves and piglets using RNA-PAGE, RT-PCR and LFA was found to be 35% (35/100), 8% (8/100) and 14.16% (16/113), respectively. Higher positivity of rotavirus was recorded in male children (44.26%, 27/61) than in female children (20.51%, 8/39). The kappa agreement between LFA and RT-PCR was 0.79 (substantial agreement); between LFA and RNA-PAGE was 0.61 (substantially low agreement) and between RNA-PAGE and RT-PCR was found to be 0.75 (substantial agreement). Relative diagnostic sensitivity and specificity of LFA in comparison with RT-PCR was 74.54% and 98.44%, respectively and in comparison with RNA-PAGE was 72.97% and 93.47%, respectively. RNA-PAGE in comparison with RT-PCR is having diagnostic sensitivity and specificity of 65.45% and 99.6%, respectively. In conclusion, the ICT strip assay is a rapid, convenient and effective method with satisfactory efficacy for detection of RVA from children, calves and piglets. ICT fulfilled the WHO ASSURED (Affordable, Sensitive, Specific, User-friendly, Rapid and robust, Equipment-free and Delivered) criteria for point-of-care testing. It can be useful in determining rotavirus outbreaks in resource-limited settings.