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Streptococcus parauberis, a gram-positive bacterium, causes significant mortality in cultured fish. In Korea, S. parauberis exhibits diverse serotypes (Ia, Ib/c, and II) from diseased fish including olive flounder (Paralichthys olivaceus), each with different pathogenicity. Therefore, the development of a reliable detection and serotyping assay is essential for effective disease surveillance. From the biochemical traits, although S. parauberis can be categorized into two subgroups associated with serotypes I and II, based on pyrrolidonyl arylamidase (PYR) activity, biochemical characterization is limited in differentiating between subserotypes. Furthermore, even though PCR-based serotyping assays (multiplex PCR; mPCR) have been reported, we aimed to develop an isothermal amplification-based assay for rapid and simultaneous detection and serotyping without the need for thermal cycling equipment. Based on the consensus sequence of the capsular polysaccharide (cps) locus, multiplex recombinase polymerase amplification (mRPA) primers were designed for the simultaneous detection and serotyping of S. parauberis. The optimized primer concentrations for mRPA were 280 nM for the detection of S. parauberis, 240 nM for serotypes Ia and II, and 200 nM for serotype Ib, with optimal amplification conditions determined to be 30 min at 42 °C. In the specificity test, no cross-reactivity with other fish pathogens was observed. In addition, the sensitivity of mRPA was 0.02 ng for detecting S. parauberis and serotypes Ia and Ib/c, while it was 0.2 ng for serotyping type II. Using DNA from cultured bacteria, the novel mRPA showed a detection rate consistent with that of mPCR. Moreover, using DNA from artificially infected tissues, the detection rate by mRPA was 96.7% (29/30), which was different from the results of mPCR (80%, 24/30), which exhibited an 80% detection rate. Therefore, the novel mRPA is an effective and rapid diagnostic tool for the simultaneous detection and serotyping of S. parauberis without requiring thermal cycling equipment as well as a specific bacterial culture step. [ABSTRACT FROM AUTHOR]

Since the outbreak of the new coronavirus, point-of-care diagnostics based on nucleic acid testing have become a requirement for the development of pathogen diagnostics, which require the ability to accurately, rapidly, and conveniently detect pathogens. Conventional nucleic acid amplification techniques no longer meet the requirements for pathogen detection in low-resource, low-skill environments because they require specialist equipment, complex operations, and long detection times. Therefore, recombinant polymerase amplification (RPA) is becoming an increasingly important method in today's nucleic acid detection technology because it can amplify nucleic acids in 20–30 minutes at a constant temperature, greatly reducing the dependence on specialist equipment and technicians. RPA products are primarily detected through methods such as real-time fluorescence, gel electrophoresis, lateral flow assays (LFAs), and other techniques. Among these, LFAs allow for the rapid detection of amplification products within minutes through the visualization of results, offering convenient operation and low cost. Therefore, the combination of RPA with LFA technology has significant advantages and holds broad application prospects in point-of-care (POC) diagnostics, particularly in low-resource settings. Here, we focus on the principles of RPA combined with LFAs, their application to pathogen diagnosis, their main advantages and limitations, and some improvements in the methods. [ABSTRACT FROM AUTHOR]

Background: Pseudomonas aeruginosa (P. aeruginosa) is widely distributed in air, soil, and water, human respiratory tract, intestinal tract, and skin. It can induce bloodstream infection, urinary tract infection, gastrointestinal tract infection, respiratory tract infection, etc. Conventional bacterial isolation, culture, and identification are time-consuming, and many false negative results, which cannot meet the needs of precise clinical diagnosis，and proper treatment. This study aims to develop a rapid isothermal amplification assay of Pseudomonas aeruginosa. Methods: Specific primers were designed according to the National Center for Biotechnology Information (NCBI) database based on the highly conserved sequence of Pseudomonas aeruginosa virulence factor gene lecA, and a recombinase polymerase amplification (RPA) detection method was established. The sensitivity and specificity were calculated, as well as the collection and processing of clinical samples. Results: The thermostatic amplification technique for Pseudomonas aeruginosa established in this paper allows nucleic acid detection within 10 minutes without cross-amplification with other bacterial strains. 27 P. aeruginosa infections were accurately detected in 300 clinical samples. Conclusion: The rapid detection system based on thermostatic amplification had shown high sensitivity and specificity in this study, indicated that this method can effectively assist clinical bacterial detection. [ABSTRACT FROM AUTHOR]

Enterocytozoon bieneusi is a common species of microsporidia that infects humans and animals. Current methods for detecting E. bieneusi infections have trade-offs in sensitivity, specificity, simplicity, cost and speed and are thus unacceptable for clinical application. We tested the effectiveness of a previously reported CRISPR/Cas12a-based method (ReCTC) when used for the nucleic acid detection of E. bieneusi. The limit of detection (LOD) and the specificity of the expanded ReCTC were evaluated using prepared target DNA, and the accuracy of the ReCTC-based detection of E. bieneusi in clinical samples was validated. The ReCTC method was successfully used for the nucleic acid detection of E. bieneusi. The sensitivity test indicated an LOD of 3.7 copies/µl for the ReCTC-based fluorescence and lateral flow strip methods. In specificity test involving other common enteric pathogens, a fluorescent signal and/or test line appeared only when the sample was positive for E. bieneusi. These results demonstrated that the ReCTC method can successfully detect E. bieneusi in clinical samples. The ReCTC method was successfully used to detect E. bieneusi nucleic acid with high sensitivity and specificity. It had excellent performance in clinical DNA samples and was superior to nested polymerase chain reaction. Furthermore, the ReCTC method demonstrated its capability for use in on-site detection. [ABSTRACT FROM AUTHOR]

ABSTRACT Spiroplasma eriocheiris is a pathogen in the Chinese mitten crab Eriocheir sinensis and is associated with tremor disease. S. eriocheiris infects virtually all artificially bred crustaceans, resulting in significant economic losses to the aquaculture industry in China. Recombinase polymerase amplification (RPA) is considered a promising technology for the rapid and sensitive detection of disease. For the rapid detection of S. eriocheiris, this study established basic RPA, RPA‐EXO and RPA‐LFD, which were visualised via agarose gel electrophoresis, SYBR Green I, fluorescence signals and test lines on lateral flow dipsticks. Specific primers and probes were designed based on the 16S ribosomal RNA sequence of S. eriocheiris. The optimal primer pairs for the basic RPA, RPA‐EXO and RPA‐LFD were RPA‐F3/R3, RPA‐F3/R3 and RPA‐LFD‐F3/R3, respectively. The optimal temperatures and times of basic RPA, RPA‐EXO and RPA‐LFD were 37°C for 25 min, 39°C for 30 min and 39°C for 10 min, respectively. The specificity test indicated that in addition to the positive test results for S. eriocheiris, the other five DNA templates tested negative, demonstrating strong specificity. The results of the sensitivity test revealed that the detection limits of RPA, RPA‐EXO and RPA‐LFD were 5.77 × 10−2, 5.77 × 10−4 and 1.52 × 10−6 ng/μL, respectively, indicating high sensitivity. This study established three methods for the detection of S. eriocheiris that are characterised by a constant temperature, rapid response, high sensitivity and strong specificity. [ABSTRACT FROM AUTHOR]

Background: Giardia duodenalis is a common enteric protozoan parasite that is categorized into eight assemblages (A–H). In particular, assemblages A and B are zoonotic, capable of infecting both humans and animals worldwide, resulting in significant economic losses and public health challenges in epidemic regions. Thus, the development of rapid, accurate and non-laboratory-based diagnostic methods for infected animals is crucial for the effective prevention and control of giardiasis. Recent advancements in clustered, regularly interspaced, short palindromic repeats (CRISPR) and CRISPR-associated (Cas) protein (Cas12a) systems allow promising avenues for nucleic acid detection, characterized by their high flexibility, sensitivity and specificity. Methods: Combined recombinase polymerase amplification and CRISPR/Cas12a systems were combined and used as end-point diagnostic methods (termed REPORT) to detect G. duodenalis assemblage A and B. The diagnostic results can be observed by fluorescence readouts with the naked eye under blue light or colorimetric signals using a lateral flow strip (LFS). Results: The limit of detection (LOD) of the REPORT‑based G. duodenalis assemblage A detection was 2.04 CFU/ml and 10 trophozoites per gram (TPG), and the LOD of assemblage B was 1.1 CFU/ml and 10 cysts per gram (CPG). The REPORT‑based G. duodenalis assemblage A and assemblage B detection methods have strong specificity and no cross-reactivity with other assemblages of G. duodenalis or common enteric parasitic protozoa and have excellent performance in clinical sample detection. Conclusions: This study presents a novel strategy for the direct identification of G. duodenalis assemblages A and B, requiring neither highly trained personnel nor costly specialized equipment. [ABSTRACT FROM AUTHOR]

The worldwide spread of carbapenemase-producing Enterobacterales (CPE) represents a significant threat owing to the high mortality and morbidity rates. Traditional diagnostic methods are often too slow and complex for rapid point-of-care testing. Therefore, we developed a recombinase polymerase amplification (RPA)-coupled CRISPR/Cas12a system (RCCS), a rapid, accurate, and simple diagnostic platform for detecting antimicrobial-resistant genes. The RCCS detected carbapenemase genes (blaKPC and blaNDM) within 50 min, including 10 min for DNA extraction and 30–40 min for RCCS reaction (a 20 min RPA reaction with a 10–20-min CRISPR/Cas12a assay). Fluorescence signals obtained from the RCCS platform were visualized using lateral-flow test strips (LFSs) and real-time and endpoint fluorescence. The LFS clearly displayed test lines while detecting carbapenemase genes. Furthermore, the RCCS platform demonstrated high sensitivity by successfully detecting blaKPC and blaNDM at the attomolar and picomolar levels, respectively. The accuracy of the RCCS platform was validated with clinical isolates of Klebsiella pneumoniae and Escherichia coli; a 100% detection accuracy was achieved, which has not been reported when using conventional PCR. Overall, these findings indicate that the RCCS platform is a powerful tool for rapid and reliable detection of carbapenemase-encoding genes, with significant potential for implementation in point-of-care settings and resource-limited environments. [ABSTRACT FROM AUTHOR]

Background/Objectives: The emergence of the mobilized colistin resistance 1 (mcr-1) gene, which causes colistin resistance, is a serious concern in animal husbandry, particularly in pigs. Although antibiotic regulations in many countries have prohibited the use of colistin in livestock, the persistence and dissemination of this plasmid-mediated gene require effective and rapid monitoring. Therefore, a rapid, sensitive, and specific method combining recombinase polymerase amplification (RPA) with an in-house lateral flow assay (LFA) for the mcr-1 gene detection was developed. Methods: The colistin agar test and broth microdilution were employed to screen 152 E. coli isolates from pig fecal samples of five antibiotic-used farms. The established RPA-in-house LFA was validated with PCR for mcr-1 gene detection. Results: The RPA-in-house LFA was completed within 35 min (20 min of amplification and 5–15 min on LFA detection) at 37 °C. The sensitivity, specificity, and accuracy were entirely 100% in concordance with PCR results. No cross-reactivity was detected with seven common pathogenic bacteria or other mcr gene variants. Conclusions: Therefore, the in-house RPA-LFA serves as a point-of-care testing tool that is rapid, simple, and portable, facilitating effective surveillance of colistin resistance in both veterinary and clinical settings, thereby enhancing health outcomes. [ABSTRACT FROM AUTHOR]

Abstract Chikungunya (CHIKV), o’nyong-nyong (ONNV), and Mayaro (MAYV) viruses are transmitted by mosquitoes and known to cause a debilitating arthritogenic syndrome. These alphaviruses have emerged and re-emerged, leading to outbreaks in tropical and subtropical regions of Asia, South America, and Africa. Despite their prevalence, there persists a critical gap in the availability of sensitive and virus-specific point-of-care (POC) diagnostics. Traditional immunoglobulin-based tests such as enzyme-linked immunosorbent assay (ELISA) often yield cross-reactive results due to the close genetic relationship between these viruses. Molecular diagnostics such as quantitative polymerase chain reaction (qPCR) offer high sensitivity but are limited by the need for specialized laboratory equipment. Recombinase polymerase amplification (RPA), an isothermal amplification method, is a promising alternative to qPCR, providing rapid results with minimal equipment requirements. Here, we report the development and validation of three virus-specific RT-RPA-based rapid tests for CHIKV, ONNV, and MAYV. These tests demonstrated both speed and sensitivity, capable of detecting 10–100 viral copies within 20 min of amplification, without exhibiting cross-reactivity. Furthermore, we evaluated the clinical potential of these tests using serum and tissue samples from CHIKV, ONNV, and MAYV-infected mice, as well as CHIKV-infected human patients. We demonstrate that the RPA amplicons derived from the patient samples can be sequenced, enabling cost-effective molecular epidemiological studies. Our findings highlight the significance of these rapid and specific diagnostics in improving the early detection and management of these arboviral infections, particularly in resource-limited settings.

Background Pseudomonas aeruginosa (P. aeruginosa) is widely distributed in air, soil, and water, human respiratory tract, intestinal tract, and skin. It can induce bloodstream infection, urinary tract infection, gastrointestinal tract infection, respiratory tract infection, etc. Conventional bacterial isolation, culture, and identification are time-consuming, and many false negative results, which cannot meet the needs of precise clinical diagnosis，and proper treatment. This study aims to develop a rapid isothermal amplification assay of Pseudomonas aeruginosa.Methods Specific primers were designed according to the National Center for Biotechnology Information (NCBI) database based on the highly conserved sequence of Pseudomonas aeruginosa virulence factor gene lecA, and a recombinase polymerase amplification (RPA) detection method was established. The sensitivity and specificity were calculated, as well as the collection and processing of clinical samples.Results The thermostatic amplification technique for Pseudomonas aeruginosa established in this paper allows nucleic acid detection within 10 minutes without cross-amplification with other bacterial strains. 27 P. aeruginosa infections were accurately detected in 300 clinical samples.Conclusion The rapid detection system based on thermostatic amplification had shown high sensitivity and specificity in this study, indicated that this method can effectively assist clinical bacterial detection.

Abstract Enterocytozoon bieneusi is a common species of microsporidia that infects humans and animals. Current methods for detecting E. bieneusi infections have trade-offs in sensitivity, specificity, simplicity, cost and speed and are thus unacceptable for clinical application. We tested the effectiveness of a previously reported CRISPR/Cas12a-based method (ReCTC) when used for the nucleic acid detection of E. bieneusi. The limit of detection (LOD) and the specificity of the expanded ReCTC were evaluated using prepared target DNA, and the accuracy of the ReCTC-based detection of E. bieneusi in clinical samples was validated. The ReCTC method was successfully used for the nucleic acid detection of E. bieneusi. The sensitivity test indicated an LOD of 3.7 copies/µl for the ReCTC-based fluorescence and lateral flow strip methods. In specificity test involving other common enteric pathogens, a fluorescent signal and/or test line appeared only when the sample was positive for E. bieneusi. These results demonstrated that the ReCTC method can successfully detect E. bieneusi in clinical samples. The ReCTC method was successfully used to detect E. bieneusi nucleic acid with high sensitivity and specificity. It had excellent performance in clinical DNA samples and was superior to nested polymerase chain reaction. Furthermore, the ReCTC method demonstrated its capability for use in on-site detection.

Abstract Background Giardia duodenalis is a common enteric protozoan parasite that is categorized into eight assemblages (A–H). In particular, assemblages A and B are zoonotic, capable of infecting both humans and animals worldwide, resulting in significant economic losses and public health challenges in epidemic regions. Thus, the development of rapid, accurate and non-laboratory-based diagnostic methods for infected animals is crucial for the effective prevention and control of giardiasis. Recent advancements in clustered, regularly interspaced, short palindromic repeats (CRISPR) and CRISPR-associated (Cas) protein (Cas12a) systems allow promising avenues for nucleic acid detection, characterized by their high flexibility, sensitivity and specificity. Methods Combined recombinase polymerase amplification and CRISPR/Cas12a systems were combined and used as end-point diagnostic methods (termed REPORT) to detect G. duodenalis assemblage A and B. The diagnostic results can be observed by fluorescence readouts with the naked eye under blue light or colorimetric signals using a lateral flow strip (LFS). Results The limit of detection (LOD) of the REPORT‑based G. duodenalis assemblage A detection was 2.04 CFU/ml and 10 trophozoites per gram (TPG), and the LOD of assemblage B was 1.1 CFU/ml and 10 cysts per gram (CPG). The REPORT‑based G. duodenalis assemblage A and assemblage B detection methods have strong specificity and no cross-reactivity with other assemblages of G. duodenalis or common enteric parasitic protozoa and have excellent performance in clinical sample detection. Conclusions This study presents a novel strategy for the direct identification of G. duodenalis assemblages A and B, requiring neither highly trained personnel nor costly specialized equipment. Graphical Abstract

Goal: This study introduced a proof-of-concept prototype for isothermal recombinase polymerase amplification (RPA) with miniaturized photometric detection, enabling rapid P. aeruginosa detection. Methods: The researchers conducted the amplification process within a microchamber with a diameter of 10 mm, utilizing a standalone Thermostat driven thermal management setup. RPA, an amplification technique was employed, which required a lower operating temperature of 37 °C–40 °C to complete the reaction. The amplified amplicon was labeled with a fluorophore reporter, stimulated by an LED light source, and detected in real-time using a photodiode. Results: The developed prototype successfully demonstrated the rapid detection of P. aeruginosa using the RPA assay. The process only required the utilization of 0.04 ng of working concentration of DNA. The entire process, from amplification to detection, could be completed in over 15 minutes. The platform showed enhanced sensitivity and specificity, providing a cost-effective and accurate solution for on-site detection/quantification of pathogens. Conclusions: The integration of isothermal RPA with the miniaturized photometric detection platform proved successful in achieving the goal of rapid and specific pathogen detection. This study proved the benefits of Isothermal Nucleic Acid Amplification Technology (INAAT), emphasizing its potential as an accessible, user-friendly point-of-care technology for resource-constrained institutions. The RPA-based prototype demonstrated capability without requiring costly laboratory equipment or expertise. The developed platform, when combined with Internet of Things (IoT) enabled cloud platform, also allowed remote monitoring of data. Overall, the methodology presented in this study offered a cost-effective, accurate, and convenient solution for on-site testing in resource-limited settings.

ABSTRACT: Salmonella is a major cause of foodborne diseases worldwide. Conventional rapid assays for detecting Salmonella in real samples often encounter severe matrix interference or detect a limited number of species of a genus, resulting in inaccurate detection. In this study, we developed a method that combined phage-based magnetic capture with real-time recombinase polymerase amplification (RPA) for the rapid, highly sensitive, and specific detection of Salmonella in milk with an ultra-low detection limit. The Felix O-1 phage-conjugated magnetic beads (O-1 pMBs) synthesized in this method showed excellent capture ability for Salmonella spp. and ideal specificity for non-Salmonella strains. After O-1 pMBs-based magnetic separation, the limit of detection of the real-time RPA assay was 50 cfu/mL in milk samples, which was significantly increased by a magnitude of 3 to 4 orders. The method exhibited a high sensitivity (compatibility) of 100% (14/14) for all tested Salmonella serotype strains and an ideal specificity (exclusivity) of 100% (7/7) for the tested non-Salmonella strains. The entire detection process, including Salmonella capture, DNA extraction, and real-time RPA detection, was completed within 1.5 h. Furthermore, milk samples spiked with 10 cfu/25 mL of Salmonella were detected positive after being cultured in buffered peptone water for only 3 h. Therefore, the proposed method could be an alternative for the rapid and accurate detection of Salmonella.

Abstract Pneumocystis jirovecii is a prevalent opportunistic fungal pathogen that can lead to life-threatening Pneumocystis pneumonia in immunocompromised individuals. Given that timely and accurate diagnosis is essential for initiating prompt treatment and enhancing patient outcomes, it is vital to develop a rapid, simple, and sensitive method for P. jirovecii detection. Herein, we exploited a novel detection method for P. jirovecii by combining recombinase polymerase amplification (RPA) of nucleic acids isothermal amplification and the trans cleavage activity of Cas12a. The factors influencing the efficiency of RPA and Cas12a-mediated trans cleavage reaction, such as RPA primer, crRNA, the ratio of crRNA to Cas12a and ssDNA reporter concentration, were optimized. Our RPA-Cas12a-based fluorescent assay can be completed within 30–40 min, comprising a 25–30 min RPA reaction and a 5–10 min trans cleavage reaction. It can achieve a lower detection threshold of 0.5 copies/µL of target DNA with high specificity. Moreover, our RPA-Cas12a-based fluorescent method was examined using 30 artificial samples and demonstrated high accuracy with a diagnostic accuracy of 93.33%. In conclusion, a novel, rapid, sensitive, and cost-effective RPA-Cas12a-based detection method was developed and demonstrates significant potential for on-site detection of P. jirovecii in resource-limited settings.

Abstract Environmental DNA (eDNA) monitoring of species distribution has become a critical tool in ecology, conservation biology and fisheries for identifying the presence and distribution of diverse organisms, including important, threatened and invasive species. However, eDNA detection still has room for improvement in sensitivity, requiring time‐consuming real‐time polymerase chain reaction (qPCR) steps and costly machines. In this study, we report a CRISPR‐Cas13‐based method for rapid, easy, sensitive, low‐cost and on‐site detection of eDNA. The assay for the detection of common carp (Cyprinus carpio) and medaka (Oryzias latipes) nucleic acid employs a two‐step process, starting with recombinase polymerase amplification (RPA) and followed by cleavage using Cas13 nuclease, to effectively identify mitochondrial DNA or RNA. Our results showed that the Cas13‐based method has a higher sensitivity than the qPCR‐based method in detecting tiny amounts of eDNA. When combined with reverse transcription of environmental RNA (eRNA), our method increased detection sensitivity by approximately one order of magnitude. Cas13‐based detection could achieve on‐site detection of eDNA using a quick nucleic acid extraction solution and lateral flow strips. Cas13‐based detection of eDNA and eRNA requires minimal training efforts and can be performed in 1 h, without the need for centrifugation and qPCR machines. The portability of the Cas13‐based method, along with its accuracy and relative ease in designing primers and CRISPR RNA (crRNA), underscores its potential to broaden the application of eDNA and eRNA in various fields, including biodiversity conservation.

This study is committed to developing and optimizing a rapid nucleic acid preparation reagent (nucleic acid release agent) that is suitable for recombinase polymerase amplification with lateral flow dipstick (RPA-LFD) technology to detect DNA nucleic acid samples in shrimp hepatopancreas to realize on-site rapid detection and remove the cumbersome and time-consuming steps of conventional nucleic acid sample extraction.The optimum compositions of nucleic acid release agent are 20–100 mmol/L Tris-HCl, 50–250 mmol/L KCl, 0.01%–0.10% (W/V) lithium dodecyl sulfate (LDS), 0.5%–2.0% (V/V) Triton X-100, 1–5 mmol/L ethylenediaminetetraacetic acid disodium salt (EGTA2Na), 0.5–5.0 mmol/L bovine serum albumin (BSA), 1–5 mg/ml gelatin, 0.01%–0.10% (W/V) trehalose, and 1%–5% (W/V) betaine. The proportion of each component of nucleic acid release agent was optimized using positive and negative samples of shrimp Enterocytozoon hepatopenaei (EHP). The RPA-LFD reaction initially involved collecting shrimp hepatopancreas (the size of a mung bean), adding 100 μL nucleic acid release agent, heating for 3 min at 100 ℃ and using the supernatant for analysis. The optimal ratio of each component of nucleic acid releaser was determined to be 100 mmol/L Tris-HCl, 100 mmol/L KCl, 0.02% LDS, 0.5% Triton X-100, 1 mmol/L EGTA2Na, 0.05% trehalose, 1 mg/mL gelatin, 0.5 mmol/L BSA, and 2% betaine. The positive and negative samples of acute hepatopancreatic necrosis disease (AHPND) were used as detection templates to verify the optimized nucleic acid release agent. The optimized nucleic acid release agent could be used to prepare nucleic acid samples, and the prepared samples were available for RPA-LFD method testing. The optimized nucleic acid release agent in this study can be used to prepare DNA nucleic acid samples of the shrimp hepatopancreas for RPA-LFD detection. It avoids the tedious and time-consuming preparation steps of conventional DNA nucleic acid samples and greatly improves the efficiency of nucleic acid level pathogen detection.Disease is the bottleneck that restricts the green development of the shrimp breeding industry, which can cause huge annual economic losses. Detection and monitoring of shrimp related pathogens are effective to solve this problem. Enterocytozoon hepatopopenaei (EHP) and Vibrio parahaemolyticus (VP) are two common pathogenic microorganisms in shrimp culturing that cause AHPND. E. hepatopopenaei is an obligate intracellular parasite that mainly parasitizes in the hepatopancreas of shrimp. Severe EHP infections lead to atrophy of the hepatopancreas of shrimp. E. hepatopopenaei has a wide range of hosts, including Penaeus vannamei, P. monodon, and Palaemon carincauda. AHPND is an aquatic disease caused by Vibrio parahemolvticus with the virulent plasmid PirA/B. It was first found in China and Vietnam in 2010, then in Malaysia, Thailand, Mexico, the Philippines, and other countries. P. monodon, P. vannamei, P. chinensis, and P. japonicus are susceptible hosts. The distribution of pathogenic vibrio can be detected in the hepatopancreas tissue of diseased shrimp, and it can cause hepatopancreas atrophy. Broadly, most shrimp pathogens (such as DIV1, WSSV, TSV, and IHHNV) infect the hepatopancreas of shrimp. DIV1 infections cause pale atrophy of the hepatopancreas. Histopathological examination identified eosinophils and dark eosinophilic inclusions in the cytoplasm of the hepatopancreas of shrimp infected with DIV1. Some of them were coated or contained slight basophilic staining, and hemocytes were pyknotic. WSSV and TSV can cause pale atrophy symptoms of the hepatopancreas, while IHHNV can also cause hepatopancreas enlargement of shrimp. Therefore, the nucleic acid samples of the hepatopancreas of shrimp can be widely used as templates for detection of most shrimp pathogens.Isothermal nucleic acid amplification technology removes the dependence on conventional nucleic acid temperature change amplification using the PCR amplification instrument, and is widely used for rapid detection. Currently, isothermal amplification technology covers loop mediated isothermal amplification (LAMP), strand displacement amplification (SDA) and recombinase polymerase amplification (RPA), and so on. Among them, RPA technology was developed in recent years using recombinases to promote the insertion and binding of oligonucleotide primers in DNA double strand complementary sequences, and realize exponential amplification of specific DNA regions under the action of Bsu DNA polymerase. It has a short reaction time, strong specificity, high sensitivity, and operates at a constant temperature of 37–42 ℃. It is suitable for on-site detection and analysis. The combination of RPA with the lateral flow dipstick (LFD) to read the detection results is simple to operate, fast, with high specificity and sensitivity. It is a new method suitable for rapid detection in the field. The combination of RPA-LFD technology and a simplified nucleic acid extraction method can help to realize portable on-site rapid nucleic acid detection.

The list of standard abbreviations for JDS is available at adsa.org/jds-abbreviations-24. Nonstandard abbreviations are available in the Notes. Salmonella is a major cause of foodborne diseases worldwide. Conventional rapid assays for detecting Salmonella in real samples often encounter severe matrix interference or detect a limited number of species of a genus, resulting in inaccurate detection. In this study, we developed a method that combined phage-based magnetic capture with real-time recombinase polymerase amplification (RPA) for the rapid, highly sensitive, and specific detection of Salmonella in milk with an ultra-low detection limit. The Felix O-1 phage-conjugated magnetic beads (O-1 pMBs) synthesized in this method showed excellent capture ability for Salmonella spp. and ideal specificity for non- Salmonella strains. After O-1 pMBs-based magnetic separation, the limit of detection of the real-time RPA assay was 50 cfu/mL in milk samples, which was significantly increased by a magnitude of 3 to 4 orders. The method exhibited a high sensitivity (compatibility) of 100% (14/14) for all tested Salmonella serotype strains and an ideal specificity (exclusivity) of 100% (7/7) for the tested non- Salmonella strains. The entire detection process, including Salmonella capture, DNA extraction, and real-time RPA detection, was completed within 1.5 h. Furthermore, milk samples spiked with 10 cfu/25 mL of Salmonella were detected positive after being cultured in buffered peptone water for only 3 h. Therefore, the proposed method could be an alternative for the rapid and accurate detection of Salmonella. [ABSTRACT FROM AUTHOR]

Pneumocystis jirovecii is a prevalent opportunistic fungal pathogen that can lead to life-threatening Pneumocystis pneumonia in immunocompromised individuals. Given that timely and accurate diagnosis is essential for initiating prompt treatment and enhancing patient outcomes, it is vital to develop a rapid, simple, and sensitive method for P. jirovecii detection. Herein, we exploited a novel detection method for P. jirovecii by combining recombinase polymerase amplification (RPA) of nucleic acids isothermal amplification and the trans cleavage activity of Cas12a. The factors influencing the efficiency of RPA and Cas12a-mediated trans cleavage reaction, such as RPA primer, crRNA, the ratio of crRNA to Cas12a and ssDNA reporter concentration, were optimized. Our RPA-Cas12a-based fluorescent assay can be completed within 30–40 min, comprising a 25–30 min RPA reaction and a 5–10 min trans cleavage reaction. It can achieve a lower detection threshold of 0.5 copies/µL of target DNA with high specificity. Moreover, our RPA-Cas12a-based fluorescent method was examined using 30 artificial samples and demonstrated high accuracy with a diagnostic accuracy of 93.33%. In conclusion, a novel, rapid, sensitive, and cost-effective RPA-Cas12a-based detection method was developed and demonstrates significant potential for on-site detection of P. jirovecii in resource-limited settings. [ABSTRACT FROM AUTHOR]

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Copyright of Methods in Ecology & Evolution is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Brucellosis is a zoonosis caused by Brucella, which poses a great threat to human health and animal husbandry. Pathogen surveillance is an important measure to prevent brucellosis, but the traditional method is time-consuming and not suitable for field applications. In this study, a recombinase polymerase amplification–SYBR Green I (RPAS) assay was developed for the rapid and visualized detection of Brucella in the field by targeting BCSP31 gene, a conserved marker. The method was highly specific without any cross-reactivity with other common bacteria and its detection limit was 2.14 × 104 CFU/mL or g of Brucella at 40 °C for 20 min. It obviates the need for costly instrumentation and exhibits robustness towards background interference in serum, meat, and milk samples. In summary, the RPAS assay is a rapid, visually intuitive, and user-friendly detection that is highly suitable for use in resource-limited settings. Its simplicity and ease of use enable swift on-site detection of Brucella, thereby facilitating timely implementation of preventive measures. [ABSTRACT FROM AUTHOR]

Background: Urogenital schistosomiasis is caused by the parasitic trematode Schistosoma haematobium. Sensitive and specific point-of-care diagnostics are needed for elimination of this disease. Recombinase polymerase amplification (RPA) assays meet these criteria, and an assay to diagnose S. haematobium has been developed (Sh-RPA). However, false-positive results can occur, and optimisation of reaction conditions to mitigate these is needed. Ease of use and compatibility of DNA extraction methods must also be considered. Methods: Using synthetic DNA, S. haematobium genomic DNA (gDNA), and urine samples from clinical cases, Sh-RPA reactions incorporating different betaine concentrations (0 M, 1 M, 2.5 M, 12.5 M) and the sample-to-water ratios were tested to determine effects on assay specificity and sensitivity. In addition, five commercial DNA extraction kits suitable for use in resource-limited settings were used to obtain gDNA from single S. haematobium eggs and evaluated in terms of DNA quality, quantity, and compatibility with the Sh-RPA assay. All samples were also evaluated by quantitative polymerase chain reaction (qPCR) to confirm DNA acquisition. Results: The analytical sensitivity of the Sh-RPA with all betaine concentrations was ≥ 10 copies of the synthetic Dra1 standard and 0.1 pg of S. haematobium gDNA. The addition of betaine improved Sh-RPA assay specificity in all reaction conditions, and the addition of 2.5 M of betaine together with the maximal possible sample volume of 12.7 µl proved to be the optimum reaction conditions. DNA was successfully isolated from a single S. haematobium egg using all five commercial DNA extraction kits, but the Sh-RPA performance of these kits varied, with one proving to be incompatible with RPA reactions. Conclusions: The addition of 2.5 M of betaine to Sh-RPA reactions improved reaction specificity whilst having no detrimental effect on sensitivity. This increases the robustness of the assay, advancing the feasibility of using the Sh-RPA assay in resource-limited settings. The testing of commercial extraction kits proved that crude, rapid, and simple methods are sufficient for obtaining DNA from single S. haematobium eggs, and that these extracts can be used with Sh-RPA in most cases. However, the observed incompatibility of specific kits with Sh-RPA highlights the need for each stage of a molecular diagnostic platform to be robustly tested prior to implementation. [ABSTRACT FROM AUTHOR]

Sensitive magnetic nucleic acid (NA) detection via frequency mixing magnetic detection (FMMD) requires amplified NA samples for which a reliable temperature control is necessary. The feasibility of recombinase polymerase amplification (RPA) was studied within a newly integrated temperature-controlled sensor unit of a mobile FMMD based setup. It has been demonstrated that the inherently generated heat of the low frequency (LF) excitation signal of FMMD can be utilized and controlled by means of pulse width modulation (PWM). To test control performance in a point of care (PoC) setting with changing ambient conditions, a steady state and dynamic response model for the thermal behavior at the sample position of the sensor were developed. We confirmed that in the sensor unit of the FMMD device, RPA performs similar as in a temperature-controlled water bath. For narrow steady state temperature regions, a linear extrapolation suffices for estimation of the sample position temperature, based on the temperature feedback sensor for PWM control. For any other ambient conditions, we identified and validated a lumped parameter model (LPM) performing with high estimation accuracy. We expect that the method can be used for NA amplification and magnetic detection using FMMD in resource-limited settings. [ABSTRACT FROM AUTHOR]

Aims: Clostridium perfringens is one of the major anaerobic pathogen causing food poisoning and animal enteritis. With the rise of antibiotic resistance and the restrictions of the use of antibiotic growth promoting agents (AGPs) in farming, Clostridium enteritis and food contamination have become more common. It is time-consuming and labor-intensive to confirm the detection by standard culture methods, and it is necessary to develop on-site rapid detection tools. In this study, a combination of recombinase polymerase amplification (RPA) and lateral flow biosensor (LFB) was used to visually detect C. perfringens in chicken meat and milk. Methods and results: Two sets of primers were designed for the plc gene of C. perfringens, and the amplification efficiency and specificity of the primers. Selection of primers produces an amplified fragment on which the probe is designed. The probe was combined with the lateral flow biosensor (LFB). The reaction time and temperature of RPA-LFB assay were optimized, and the sensitivity of the assay was assessed. Several common foodborne pathogens were selected to test the specificity of the established method. Chicken and milk samples were artificially inoculated with different concentrations (1 x 10² CFU/mL to 1 x 106 CFU/mL) of C. perfringens, and the detection efficiency of RPALFB method and PCR method was compared. RPA-LFB can be completed in 20 min and the results can be read visually by the LFB test strips. The RPA-LFB has acceptable specificity and the lowest detection limit of 100 pg./μL for nucleic acid samples. It was able to stably detect C. perfringens contamination in chicken and milk at the lowest concentration of 1 x 104 CFU/mL and 1 x 10³ CFU/mL, respectively. Conclusion: In conclusion, RPA-LFB is specific and sensitive. It is a rapid, simple and easy-to-visualize method for the detection of C. perfringens in food and is suitable for use in field testing work. [ABSTRACT FROM AUTHOR]

The bacterium Klebsiella pneumoniae (Kp) was the primary pathogen of hospitalacquired infection, but the current detection method could not rapidly and conveniently identify Kp. Recombinase polymerase amplification (RPA) was a fast and convenient isothermal amplification technology, and the clustered regularly interspaced short palindromic repeats (CRISPR) system could rapidly amplify the signal of RPA and improve its limit of detection (LOD). In this study, we designed three pairs of RPA primers for the rcsA gene of Kp, amplified the RPA signal through single-strand DNA reporter cleavage by CRISPR/Cas12a, and finally analyzed the cleavage signal using fluorescence detection (FD) and lateral flow test strips (LFTS). Our results indicated that the RPA-CRISPR/Cas12a platform could specifically identify Kp from eleven common clinical pathogens. The LOD of FD and LFTS were 1 fg/µL and 10 fg/µL, respectively. In clinical sample testing, the RPA-CRISPR/Cas12a platform was consistent with the culture method and qPCR method, and its sensitivity and specificity were 100% (16/16) and 100% (9/9), respectively. With the advantages of detection speed, simplicity, and accuracy, the RPA-CRISPR/Cas12a platform was expected to be a convenient tool for the early clinical detection of Kp. [ABSTRACT FROM AUTHOR]

[Objective] Mycoplasma gallisepticum（MG）and Mycoplasma synoviae（MS）are the two most harmful mycoplasmas to poultry. Early diagnosis of MG and MS was a key to prevent and control avian mycoplasma. Through combining recombinase polymerase amplification（RPA）technology with lateral flow dipstick（LFD）, a rapid detection method for MG and MS with convenient operation, rapid response and visual results was established. [Method] Specific primers and probes were designed based on MG mgc2 gene and MS vlhA gene, and a dual LFD-RPA rapid detection method was established by optimizing reaction time, reaction temperature and primer ratio, and its sensitivity, specificity and stability were evaluated. Meanwhile, 120 clinical samples were tested. [Result] The amplification was done by dual LFD-RPA detection method at 37℃ for 5-10 min, and the optimal primer ratio of RPA-MG-F2/R2 and RPA-MS-F1/R1 was 0.6 ∶ 1.4. The minimum detection limits of MG and MS were 3.75 copies/μL and 3.46 copies/μL, respectively. This method and the PCR method recommended by OIE were used to detect 120 samples, and the coincidence rate was 93.3%. [Conclusion] The amplification can be done by the dual LFDRPA detection method of MG and MS under constant temperature conditions. It has simple operation, rapid response, high sensitivity, strong specificity and good stability, and the results can be observed without using any instrument. It is suitable for the field rapid detection of MG and MS infection alone or mixed infection at the primary level. [ABSTRACT FROM AUTHOR]

Recombinase polymerase amplification (RPA) is an isothermal DNA amplification reaction at around 41 °C using recombinase (Rec), single-stranded DNA-binding protein (SSB), strand-displacing DNA polymerase (Pol), and an ATP-regenerating enzyme. Considering the onsite use of RPA reagents, lyophilized RPA reagents with long storage stability are highly desired. In this study, as one of the approaches to solve this problem, we attempted to use a thermostable pyruvate kinase (PK). PK gene was isolated from a thermophilic bacterium Thermotoga maritima (Tma -PK). Tma -PK was expressed in Escherichia coli and purified from the cells. Tma -PK exhibited higher thermostability than human PK. The purified Tma -PK preparation was applied to RPA as an ATP-regenerating enzyme. Liquid RPA reagent with Tma -PK exhibited the same performance as that with human PK. Lyophilized RPA reagent with Tma -PK exhibited higher performance than that with human PK. Combined with our previous results of RPA reagents of thermostable Pol from a thermophilic bacterium, Aeribacillus pallidus , the results in this study suggest that thermostable enzymes are preferable to mesophilic ones as a component in lyophilized RPA reagents. [ABSTRACT FROM AUTHOR]

BACKGROUND: Bactrocera correcta is a quarantine pest that negatively impacts the fruit and vegetable industry. Differentiating B. correcta from similar species, especially in non‐adult stages, remains challenging. Rapid molecular identification techniques, such as recombinase polymerase amplification (RPA) combined with CRISPR/Cas12a and multienzyme isothermal rapid amplification with lateral flow dipstick (MIRA‐LFD), play a crucial role in early monitoring and safeguarding agricultural production. Our study introduces two methods for the rapid visual identification of B. correcta. RESULTS: Bactrocera correcta specific RPA primers, CRISPR RNA (crRNA), and the LFD probe were designed based on the cox1 genes. The RPA reaction conditions were optimized (at 37 °C for 8 min) for effective template DNA amplification. Two nucleic acid detection methods were established to visualize RPA. In the RPA‐CRISPR/Cas12a system, the optimal LbCas12a/crRNA concentration ratio was 200:400 nmol L−1. Successful amplification was determined by the presence or absence of green fluorescence following 15 min incubation at 37 °C. The MIRA‐LFD system achieved precise identification of the target species within 4 min at 37 °C. Both methods exhibited high specificity and sensitivity, allowing for detection from 1.0 × 10−1 ng μL−1 of DNA. Combined with rapid DNA extraction, rapid identification of individual B. correcta at different developmental stages was achieved, enhancing the practicality and convenience of the established methods. CONCLUSION: Our research findings demonstrate that both the RPA‐CRISPR/Cas12a and MIRA‐LFD methods for B. correcta detection was accurate and rapid (within 30 min and 10 min, respectively), at 37 °C. Our methods do not rely on expensive equipment, thus possess high practical value, providing improved identification solutions for port quarantine pests and field applications. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Porcine epidemic diarrhoea virus (PEDV), a pathogenic microorganism that induces epidemic diarrhoea in swine, causes substantial economic damage to swine-farming nations. To prevent and control PEDV infections, the availability of upgraded and rapid virus detection techniques is crucial. The clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein (Cas)13a system, namely, programmability of CRISPR RNA (crRNA) and “collateral” promiscuous RNase activity of Cas13a after target RNA identification. In this study, we aimed to develop a recombinase polymerase amplification (RPA)-based CRISPR-Cas13a approach for PEDV diagnosis for the first time. The results showed that up to 10 copies of the target PEDV DNA standard/µL were detected after 40 min at 37 °C. PEDV detection exhibited remarkable specificity compared to that of other selected pathogens. Additionally, this RPA-based CRISPR-Cas13a approach could be used to clinical samples, with similar performance to that of reverse transcription-quantitative polymerase chain reaction (RT – qPCR). The results of our proposed approach were visualized using either lateral flow strips or fluorescence for field-deployable viral diagnostics, thereby facilitating its use in endemic regions. Overall, our proposed approach showed good reliability, sensitivity, and specificity, suggesting that it is applicable for detecting other viruses in diagnosing diseases and inspecting food safety.

Since the outbreak of the new coronavirus, point-of-care diagnostics based on nucleic acid testing have become a requirement for the development of pathogen diagnostics, which require the ability to accurately, rapidly, and conveniently detect pathogens. Conventional nucleic acid amplification techniques no longer meet the requirements for pathogen detection in low-resource, low-skill environments because they require specialist equipment, complex operations, and long detection times. Therefore, recombinant polymerase amplification (RPA) is becoming an increasingly important method in today’s nucleic acid detection technology because it can amplify nucleic acids in 20–30 minutes at a constant temperature, greatly reducing the dependence on specialist equipment and technicians. RPA products are primarily detected through methods such as real-time fluorescence, gel electrophoresis, lateral flow assays (LFAs), and other techniques. Among these, LFAs allow for the rapid detection of amplification products within minutes through the visualization of results, offering convenient operation and low cost. Therefore, the combination of RPA with LFA technology has significant advantages and holds broad application prospects in point-of-care (POC) diagnostics, particularly in low-resource settings. Here, we focus on the principles of RPA combined with LFAs, their application to pathogen diagnosis, their main advantages and limitations, and some improvements in the methods.

Carbapenem resistant Klebsiella pneumoniae (CRKP) can cause serious hospital- and community-acquired infections. Treatment for CRKP infection is limited, resulting in prolonged hospitalization and high consultation costs. The KPC genotype has the highest detection rate of CRKP, and its mortality rate is higher than the overall mortality rate of CRKP. However, traditional testing methods have disadvantages such as long time and reliance on complex and sophisticated instruments, which are not conducive to rapid screening for CRKP. Therefore, this study aimed to establish a detection platform for early screening of CRKP so that effective antimicrobial therapy could be administered promptly to prevent the widespread spread of CRKP. We integrated dual RPA with CRISPR/Cas12a to establish a dual platform for the detection of K. pneumoniae (Kp) rcsA-specific gene and KPC resistance gene. Four result reading methods were established, including fluorescence detection (FD), blue light irradiation detection (BLID), ultraviolet irradiation detection (UID), and lateral flow test strips (LFTS). For the rcsA gene, the LOD of FD was 1 × 10 pg/μL, and the other three methods could detect 1 × 101 pg/μL of bacterial DNA. As for the KPC gene, four resultant readout methods were able to detect 1 × 102 pg/μL of bacterial DNA. In 59 clinical strains tested, the dual RPA-CRISPR/Cas12a detection of the rcsA had 100% sensitivity, specificity, and accuracy compared to the culture method. Compared with the drug sensitivity test, the sensitivity of dual RPA-CRISPR/Cas12a detection for the KPC was 85.71%, the specificity was 100%, and the accuracy was 94.92%. In summary, our dual RPA-CRISPR/Cas12a platform proved to be rapid, precise, and convenient for the efficient detection of Kp with KPC in the laboratory or at the point of care.

Keke Li,1,* Yaozhou Wu,1,2,* Meng Liu,1 Junwen Yan,1 Lianhua Wei1 1Department of Clinical Laboratory, Gansu Provincial Hospital, Lanzhou, 730000, People’s Republic of China; 2First School of Clinical Medicine, Lanzhou University, Lanzhou, 730000, People’s Republic of China*These authors contributed equally to this workCorrespondence: Lianhua Wei; Junwen Yan, Department of Clinical Laboratory, Gansu Provincial Hospital, No. 204 Donggang West Road, Chengguan District, Lanzhou, 730000, People’s Republic of China, Email 3752131518@qq.com; 249380017@qq.comPurpose: Accurate detection and identification of pathogens and their associated resistance mechanisms are essential prerequisites for implementing precision medicine in the management of Carbapenem-resistant Enterobacterales (CRE). Among the various resistance mechanisms, the production of KPC carbapenemase is the most prevalent worldwide. Consequently, this study aims to develop a convenient and precise nucleic acid detection platform specifically for the blaKPC gene.Methods: The initial phase of our research methodology involved developing a CRISPR/Cas12a detection framework, which was achieved by designing highly specific single-guide RNAs (sgRNAs) targeting the blaKPC gene. To enhance the sensitivity of this system, we incorporated three distinct amplification techniques—polymerase chain reaction (PCR), loop-mediated isothermal amplification (LAMP), and recombinase polymerase amplification (RPA)—into the CRISPR/Cas12a framework. Subsequently, we conducted a comparative analysis of the sensitivity and specificity of these three amplification methods when used in combination with the CRISPR/Cas12a system. Additionally, we assessed the clinical applicability of the methodologies by evaluating fluorescence readouts from 80 different clinical isolates. Furthermore, we employed lateral flow assay technology to provide a visual representation of the results, facilitating point-of-care testing.Results: Following a comparative analysis of the sensitivity and specificity of the three methods, we identified the RPA-Cas12a approach as the optimal detection technique. Our findings demonstrated that the limit of detection (LoD) of the RPA-Cas12a platform was 1 aM (~1 copy/μL) for plasmid DNA and 5 × 10³ fg/μL for genomic DNA. Furthermore, both the sensitivity and specificity of the platform achieved 100% upon validation with 80 clinical isolates.Conclusion: These findings suggest that the developed RPA-Cas12a platform represents a promising tool for the cost-effective, convenient, and accurate detection of the blaKPC gene.Keywords: Klebsiella pneumoniae carbapenemase, CRISPR-Cas12a, isothermal amplification, polymerase chain reaction, loop-mediated isothermal amplification, recombinase polymerase amplification, lateral flow strips

Isothermal amplification techniques have been actively developed in recent years and are gradually introduced into the range of methods for infectious disease diagnostics. One of the fastest isothermal methods is recombinase polymerase amplification (RPA). This review contains information about the principle of RPA, the role of individual reaction components and primer design considerations. It provides information on characteristics of various methods of RPA results detection, effects of inhibitors, temperature and agitation on the efficiency of reaction. Approaches to quantitative and multiplex RPA are described, as well as some variants of portable devices designed to identify infectious agents. The conclusion summarizes advantages and disadvantages of RPA in comparison with other amplification methods.

Abstract This study aims to establish a rapid diagnostic method for Streptococcus agalactiae (GBS) based on recombinase polymerase amplification (RPA) and lateral flow strips (LFS). The best primer pairs designed by SIP gene were screened according to the basic RPA reaction, then the probe was designed. The reaction condition was optimized based on the color development of the LFS detection line. To ascertain the reaction specificity, 10 common clinical pathogens and 10 clinical specimens of GBS were tested. Furthermore, the reaction sensitivity was assessed by utilizing a tenfold gradient dilution of GBS genomic DNA as templates. RPA–LFS method was compared to the qPCR assay and biochemical culture method for the Kappa consistency test. The RPA–LFS technique was able to complete the amplification process within 30 min and the results were observed on lateral flow strips. The method is highly sensitive, with a minimum detection limit of 1.31 ng for GBS. The RPA–LFS method showed consistent accuracy of results compared to qPCR and the culture–biochemical method. The establishment of this method is conducive to the development of on-site immediate detection, which can provide information for the timely development of a reasonable antimicrobial treatment plan, and has a greater potential for clinical application.

Abstract Human bocavirus (HBoV) 1 is considered an important pathogen that mainly affects infants aged 6–24 months, but preventing viral transmission in resource‐limited regions through rapid and affordable on‐site diagnosis of individuals with early infection of HBoV1 remains somewhat challenging. Herein, we present a novel faster, lower cost, reliable method for the detection of HBoV1, which integrates a recombinase polymerase amplification (RPA) assay with the CRISPR/Cas12a system, designated the RPA‐Cas12a‐fluorescence assay. The RPA‐Cas12a‐fluorescence system can specifically detect target gene levels as low as 0.5 copies of HBoV1 plasmid DNA per microliter within 40 min at 37°C without the need for sophisticated instruments. The method also demonstrates excellent specificity without cross‐reactivity to non‐target pathogens. Furthermore, the method was appraised using 28 clinical samples, and displayed high accuracy with positive and negative predictive agreement of 90.9% and 100%, respectively. Therefore, our proposed rapid and sensitive HBoV1 detection method, the RPA‐Cas12a‐fluorescence assay, shows promising potential for early on‐site diagnosis of HBoV1 infection in the fields of public health and health care. The established RPA‐Cas12a‐fluorescence assay is rapid and reliable method for human bocavirus 1 detection. The RPA‐Cas12a‐fluorescence assay can be completed within 40 min with robust specificity and sensitivity of 0.5 copies/μl.

Abstract Background Pseudomonas aeruginosa (P. aeruginosa) is a life-threatening bacterium known for its rapid development of antibiotic resistance, posing significant challenges in clinical treatment, biosecurity, food safety, and environmental monitoring. Early and accurate identification of P. aeruginosa is crucial for effective intervention. Methods The lasB gene of P. aeruginosa was selected as the target for the detection. RPA primers for recombinase polymerase amplification (RPA) and crRNA for CRISPR/Cas12a detection were meticulously designed to target specific regions within the lasB gene. The specificity of the RPA/CRISPR/Cas12a detection platform was assessed using 15 strains. The detection limit of RPA/CRISPR/Cas12a detection platform was determined by utilizing a pseudo-dilution series of the P. aeruginosa DNA. The practical applicability of the RPA/CRISPR/Cas12a detection platform was validated by comparing it with qPCR on 150 samples (35 processed meat product samples, 55 cold seasoned vegetable dishes, 60 bottled water samples). Results The RPA/CRISPR/Cas12a detection platform demonstrates high specificity, with no cross-reactivity with non-P. aeruginosa strains. This assay exhibits remarkable sensitivity, with a limit of detection (LOD) of 100 copies/µL for fluorescence assay and 101 copies/µL for the LFTS method. Furthermore, the performance of the RPA/CRISPR/Cas12a detection platform is comparable to that of the well-established qPCR method, while offering advantages such as shorter reaction time, simplified operation, and reduced equipment requirements. Conclusions The RPA/CRISPR/Cas12a detection platform presents a straightforward, accurate, and sensitive approach for early P. aeruginosa detection and holds great promise for diverse applications requiring rapid and reliable identification.

Abstract Background While Plasmodium falciparum and Plasmodium vivax cause the majority of malaria cases and deaths, infection by Plasmodium malariae and other Plasmodium species also causes morbidity and mortality. Current understanding of these infections is limited in part by existing point-of-care diagnostics that fail to differentiate them and have poor sensitivity for low-density infections. Accurate diagnosis currently requires molecular assays performed in well-resourced laboratories. This report describes the development of a P. malariae diagnostic assay that uses rapid, isothermal recombinase polymerase amplification (RPA) and lateral-flow-strip detection. Methods Multiple combinations of custom RPA primers and probes were designed using publicly available P. malariae genomic sequences, and by modifying published primer sets. Based on manufacturer RPA reaction conditions (TwistDx nfo kit), an isothermal assay was optimized targeting the multicopy P. malariae 18S rRNA gene with 39 °C incubation and 30-min run time. RPA product was visualized using lateral strips (FAM-labeled, biotinylated amplicon detected by a sandwich immunoassay, visualized using gold nanoparticles). Analytical sensitivity was evaluated using 18S rRNA plasmid DNA, and clinical sensitivity determined using qPCR-confirmed samples collected from Tanzania, Ethiopia, and the Democratic Republic of the Congo. Results Using 18S rRNA plasmid DNA, the assay demonstrates a detection limit of 10 copies/µL (~ 1.7 genome equivalents) and 100% analytical specificity. Testing in field samples showed 95% clinical sensitivity and 88% specificity compared to qPCR. Total assay time was less than 40 min. Conclusion Combined with simplified DNA extraction methods, the assay has potential for future field-deployable, point-of-care use to detect P. malariae infection, which remains largely undiagnosed but a neglected cause of chronic malaria. The assay provides a rapid, simple readout on a lateral flow strip without the need for expensive laboratory equipment.

Phytophthora sojae is a devastating plant pathogen that causes soybean Phytophthora root rot worldwide. Early on-site and accurate detection of the causal pathogen is critical for successful management. In this study, we have developed a novel and specific one-pot RPA/PCR-CRISPR/Cas12 assay for onsite detection (Cas-OPRAD) of Phytophthora root rot (P. sojae). Compared to the traditional RPA/PCR detection methods, the Cas-OPRAD assay has significant detection performance. The Cas-OPRAD platform has excellent specificity to distinguish 33 P. sojae from closely related oomycetes or fungal species. The PCR-Cas12a assay had a consistent detection limit of 100 pg. µL-1, while the RPA-Cas12a assay achieved a detection limit of 10 pg. µL-1. Furthermore, the Cas-OPRAD assay was equipped with a lateral flow assay for on-site diagnosis and enabled the visual detection of P. sojae on the infected field soybean samples. This assay provides a simple, efficient, rapid (<1 h), and visual detection platform for diagnosing Phytophthora root rot based on the one-pot CRISPR/Cas12a assay. Our work provides important methods for early and accurate onsite detection of Phytophthora root rot in the field or customs fields. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Food Safety & Quality is the property of Journal of Food Safety & Quality Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Large yellow croaker (Larimichthys crocea) is a vital marine‐cultured species in China. Large yellow croaker iridovirus (LYCIV) can cause a high mortality rate in L. crocea. Rapid and convenient detection of LYCIV is an urgent demand for diagnosis. In this study, rapid and simple recombinase polymerase amplification (RPA), real‐time RPA and RPA combined with lateral flow dipstick (RPA‐LFD) methods were developed for the detection of LYCIV based on the conserved sequence of the LYCIV major capsid protein (MCP) gene. With these optimized RPA analyses, LYCIV detection could be completed within 20 min at 40°C. Both RPA and real‐time RPA could detect viral DNA as low as 102 copies/μL, while the detection limit of RPA‐LFD was 101 copies/μL, and there was no cross‐reaction with other aquatic pathogens (KHV, CyHV‐2, GCRV‐JX01, SVCV, LCDV and LMBV). In practical evaluation of RPA, real‐time RPA and RPA‐LFD methods, the results showed consistency with the general PCR detection. In short, the developed RPA, real‐time RPA and RPA‐LFD analyses could be simple, rapid, sensitive and reliable methods for field diagnosis of LYCIV infection and have significant potential in the protection of LYCIV infection. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Food Safety & Quality is the property of Journal of Food Safety & Quality Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Laboratory automation effectively increases the throughput in sample analysis, reduces human errors in sample processing, as well as simplifies and accelerates the overall logistics. Automating diagnostic testing workflows in peripheral laboratories and also in near-patient settings -like hospitals, clinics and epidemic control checkpoints- is advantageous for the simultaneous processing of multiple samples to provide rapid results to patients, minimize the possibility of contamination or error during sample handling or transport, and increase efficiency. However, most automation platforms are expensive and are not easily adaptable to new protocols. Here, we address the need for a versatile, easy-to-use, rapid and reliable diagnostic testing workflow by combining open-source modular automation (Opentrons) and automation-compatible molecular biology protocols, easily adaptable to a workflow for infectious diseases diagnosis by detection on paper-based diagnostics. We demonstrated the feasibility of automation of the method with a low-cost Neisseria meningitidis diagnostic test that utilizes magnetic beads for pathogen DNA isolation, isothermal amplification, and detection on a paper-based microarray. In summary, we integrated open-source modular automation with adaptable molecular biology protocols, which was also faster and cheaper to perform in an automated than in a manual way. This enables a versatile diagnostic workflow for infectious diseases and we demonstrated this through a low-cost N. meningitidis test on paper-based microarrays. [ABSTRACT FROM AUTHOR]

Purpose: Accurate detection and identification of pathogens and their associated resistance mechanisms are essential prerequisites for implementing precision medicine in the management of Carbapenem-resistant Enterobacterales (CRE). Among the various resistance mechanisms, the production of KPC carbapenemase is the most prevalent worldwide. Consequently, this study aims to develop a convenient and precise nucleic acid detection platform specifically for the blaKPC gene. Methods: The initial phase of our research methodology involved developing a CRISPR/Cas12a detection framework, which was achieved by designing highly specific single-guide RNAs (sgRNAs) targeting the blaKPC gene. To enhance the sensitivity of this system, we incorporated three distinct amplification techniques—polymerase chain reaction (PCR), loop-mediated isothermal amplification (LAMP), and recombinase polymerase amplification (RPA)—into the CRISPR/Cas12a framework. Subsequently, we conducted a comparative analysis of the sensitivity and specificity of these three amplification methods when used in combination with the CRISPR/Cas12a system. Additionally, we assessed the clinical applicability of the methodologies by evaluating fluorescence readouts from 80 different clinical isolates. Furthermore, we employed lateral flow assay technology to provide a visual representation of the results, facilitating point-of-care testing. Results: Following a comparative analysis of the sensitivity and specificity of the three methods, we identified the RPA-Cas12a approach as the optimal detection technique. Our findings demonstrated that the limit of detection (LoD) of the RPA-Cas12a platform was 1 aM (~1 copy/μL) for plasmid DNA and 5 × 10³ fg/μL for genomic DNA. Furthermore, both the sensitivity and specificity of the platform achieved 100% upon validation with 80 clinical isolates. Conclusion: These findings suggest that the developed RPA-Cas12a platform represents a promising tool for the cost-effective, convenient, and accurate detection of the blaKPC gene. [ABSTRACT FROM AUTHOR]

Suitable sample collection and preparation methods are essential to enable nucleic acid amplification testing at the point of care (POC). Strategies that allow direct isothermal nucleic acid amplification testing (iNAAT) of crude sample lysate without the need for nucleic acid extraction minimize time to result as well as the need for operator expertise and costly infrastructure. The authors review research to understand how sample matrix and preparation affect the design and performance of POC iNAATs. They focus on approaches where samples are directly combined with liquid reagents for preparation and amplification via iNAAT strategies. They review factors related to the type and method of sample collection, storage buffers, and lysis strategies. Finally, they discuss RNA targets and relevant regulatory considerations. Limitations in sample preparation methods are a significant technical barrier preventing implementation of nucleic acid testing at the POC. The authors propose a framework for co-designing sample preparation and amplification steps for optimal performance with an extraction-free paradigm by considering a sample matrix and lytic strategy prior to an amplification assay and readout. In the next 5 years, the authors anticipate increasing priority on the co-design of sample preparation and iNAATs. [ABSTRACT FROM AUTHOR]

Phytophthora nicotianae is a global and polyphagous pathogen with a wide host range. P. nicotianae can infect Areca catechu, Durio zibethinus L., Psidium guajava L., Hevea brasiliensis, and other tree species. The pathogen is capable of inducing butt rot and affecting aerial parts, including stems, leaves, and fruits. Compared to other Phytophthora species, P. nicotianae is more adaptable to abiotic stress. In this study, recombinase polymerase amplification (RPA) in combination with the CRISPR/Cas12a system was used for the detection of P. nicotianae, and achieved rapid and efficient detection of P. nicotianae. The assay was highly specific to P. nicotianae. All 4 tested isolates of P. nicotianae yielded positive results, whereas 30 isolates belonging to 17 other Phytophthora species, 8 fungal species, and 4 Bursaphelenchus xylophilus vermicules lacked detection. Under the conditions of 37 °C, after 20 min of RPA reaction and 25 min of Cas12a cleavage, a DNA concentration as low as 10 pg·μL−1 could be detected. In addition, it detected P. nicotianae from artificially inoculated leaves of Fatsia japonica. In this study, a novel method was established for the efficient and accurate detection of P. nicotianae based on the combination of RPA and the CRISPR/Cas12a system. [ABSTRACT FROM AUTHOR]

This study aims to establish a rapid diagnostic method for Streptococcus agalactiae (GBS) based on recombinase polymerase amplification (RPA) and lateral flow strips (LFS). The best primer pairs designed by SIP gene were screened according to the basic RPA reaction, then the probe was designed. The reaction condition was optimized based on the color development of the LFS detection line. To ascertain the reaction specificity, 10 common clinical pathogens and 10 clinical specimens of GBS were tested. Furthermore, the reaction sensitivity was assessed by utilizing a tenfold gradient dilution of GBS genomic DNA as templates. RPA–LFS method was compared to the qPCR assay and biochemical culture method for the Kappa consistency test. The RPA–LFS technique was able to complete the amplification process within 30 min and the results were observed on lateral flow strips. The method is highly sensitive, with a minimum detection limit of 1.31 ng for GBS. The RPA–LFS method showed consistent accuracy of results compared to qPCR and the culture–biochemical method. The establishment of this method is conducive to the development of on-site immediate detection, which can provide information for the timely development of a reasonable antimicrobial treatment plan, and has a greater potential for clinical application. [ABSTRACT FROM AUTHOR]

The Chinese giant salamander (Andrias davidianus), listed as an endangered species under "secondary protection" in China, faces significant threats due to ecological deterioration and the expansion of human activity. Extensive field investigations are crucial to ascertain the current status in the wild and to implement effective habitat protection measures to safeguard this species and support its population development. Traditional survey methods often fall short due to the elusive nature of the A. davidianus, presenting challenges that are time-consuming and generally ineffective. To overcome these obstacles, this study developed a real-time monitoring method that uses environmental DNA (eDNA) coupled with recombinase polymerase amplification and lateral flow strip (RPA-LFD). We designed five sets of species-specific primers and probes based on mitochondrial genome sequence alignments of A. davidianus and its close relatives. Our results indicated that four of these primer/probe sets accurately identified A. davidianus, distinguishing it from other tested caudata species using both extracted DNA samples and water samples from a tank housing an individual. This method enables the specific detection of A. davidianus genomic DNA at concentrations as low as 0.1 ng/mL within 50 min, without requiring extensive laboratory equipment. Applied in a field survey across four sites in Huangshan City, Anhui Province, where A. davidianus is known to be distributed, the method successfully detected the species at three of the four sites. The development of these primer/probe sets offers a practical tool for field surveying and monitoring, facilitating efforts in population recovery and resource conservation for A. davidianus. [ABSTRACT FROM AUTHOR]

Hepatitis E virus (HEV) is the leading cause of acute viral hepatitis worldwide. HEV RNA detection is the gold standard for HEV infection diagnosis and PCR methods are commonly used but are usually time-consuming and expensive, resulting in low detection efficiency and coverage, especially in low-income areas. Here, we developed a simpler and more accessible HEV RNA detection method based on CRISPR-Cas13a system. A total of 265 samples of different types and sources, including 89 positive samples and 176 negative samples, were enrolled for evaluations. The sensitivity and specificity of the Cas13a-crRNA detection system were evaluated. The World Health Organization reference panel for HEV genotypes was used to evaluate the capability for detecting different HEV genotypes. The validity of the assay was compared with RT-qPCR. The 95 % limits of detection (LOD) of Cas13a-crRNA-based fluorescence assay and strip assay were 12.5 and 200 IU/mL, respectively. They did not show cross-reactivity with samples positive for hepatitis A virus, hepatitis B virus, hepatitis C virus, coxsackievirus A16, rotavirus, enterovirus 71, norovirus or enteropathic Escherichia coli. Different HEV genotypes (HEV1–4) can be detected by the assay. Compared to RT-qPCR, the positive predictive agreements of Cas13a-crRNA-based fluorescence and strip assay were 98.9 % (95 % CI: 93.9–99.8 %) and 91.0 % (95 % CI: 83.3–95.4 %), respectively. The negative predictive agreements were both 100 % (95 % CI: 97.8–100 %). In conclusion, we established a rapid and convenient HEV RNA detection method with good sensitivity and specificity based on CRISPR-Cas13a system, providing a new option for HEV infection diagnosis. [ABSTRACT FROM AUTHOR]