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Based on recombinase polymerase amplification (RPA) detection technology (combined with (lateral flow dipstick, LFD)), it is aimed to establish a dual recombinase polymerase amplification method for the rapid identification of Pasteurella multocida (Pm) and Actinobacillus pleuropneumoniae (APP). The conserved fragments of Pm kmt1 gene and APP ApxIV gene were selected for the amplification of target fragments. Eight pairs of primers for Pm and APP, and one probe for KMT1Pn and APP323Pn were designed. A single RPA-Basic primer screening test was performed. The reaction time and temperature of double RPA were optimized. The optimal primers and probe matching systems of dual RPA-LFD were explored. Dual RPA sensitivity and specificity tests were performed. The method was used to detect 60 clinical samples. The results of the primer screening test showed that the primers had the strongest specificity and the highest amplification efficiency for ApxIV2698F/ApxIV3020R and KMT1F/KMT1R. The method had the best amplification efficiency at a reaction temperature of 37ºC and a reaction time of 35 min. The optimal primer ratio of KMT1F/KMT1R and ApxIV2698F/ ApxIV3020R was 2 μL : 1.5 μL, and the optimal probe ratio of KMT1Pn and APP323Pn was 0.6 μL : 0.4 μL. The minimum detection limit of dual RPA-Basic and RPA-LFD sensitivity test was 10-6 ng/μL. The specific test results showed no cross-reaction with enteropathogenic Escherichia coli, Salmonella, Glaesserella parasuis, Staphylococcus aureus, Streptococcus suis, Aeromonas hydrophila. Using 60 clinical samples of suspected Pm and/or APP infection to evaluate the detection system, the detection rate of dual RPA-Basic and RPA-LFD is higher than that of PCR, indicating that they have strong practicability. This study successfully established a dual RPA-Basic and RPA-LFD detection method for Pm and APP, which can be used for the rapid differential diagnosis of Pm and APP mixed infection in clinical. [ABSTRACT FROM AUTHOR]

Background: Porcine teschovirus (PTV) is an important enteropathogen, associated with symptoms of polioencephalomyelitis, pneumonia, pericarditis, myocarditis, diarrhea, and reproductive disorders in pigs. Rapid and precise diagnostic methods are essential for managing PTV infections. The study introduced a simple, quick, and visual approach for detecting PTV through the use of RT-RAA coupled with LFD. Results: The procedures of RT-RAA-LFD for PTV could be carried out with 1.0 μmol/L primer concentration and 2.0 μmol/L probe concentration at 37 °C for 20 min, and the amplification result could be visualized within 5 min through LFD detection. Meanwhile, the assay established in this study showed no interaction with other associated diarrhea viruses, and has high specificity to PTV, with a minimal detection limit of 10 copies/μL and good repeatability. 128 clinical samples suspected of having a PTV infection were tested by RT-PCR and RT-RAA-LFD, respectively. The total diagnostic coincidence rate was 98.44% (126/128) with a Kappa value of 0.96(K ≥ 0.75), demonstrating a high degree of agreement to detect PTV for the two methods. Conclusions: The RT-RAA-LFD assay created in this research displayed quick response, specificity, and sensitivity, capable of successfully detecting PTV in less than 25 min, providing an easy-to-use diagnostic instrument for rapid and visual PTV detection, especially suitable for labs and low-resource environments. [ABSTRACT FROM AUTHOR]

Background: Senecavirus A (SVA) is a newly pathogenic virus correlated with the acute death of piglets and vesicular lesions in pigs. The further prevalence of SVA will cause considerable economic damage to the global pig farming industry. Therefore, rapid and accurate diagnostic tools for SVA are crucial for preventing and controlling the disease. Methods: We designed multiple primer pairs targeting the most conserved region of the SVA 3D gene and selected those with the highest specificity. Nfo-probes were subsequently developed based on the highest specificity primer pairs. Subsequently, the recombinase-assisted amplification (RAA) reaction was completed, and the reaction temperature and duration were optimized. The RAA amplicons were detected using a lateral flow device (LFD). Finally, a rapid and intuitive RAA-LFD assay was established against SVA. Results: The SVA RAA-LFD assay can be performed under reaction conditions of 35°C within 17 minutes, with results observable to the naked eye. We then evaluated the performance of this method. It exhibited high specificity and no cross-reaction with the other common swine pathogens. The lowest detectable limits of this method for the plasmid of pMD18-SVA-3D, DNA amplification product, and viral were 3.86×101 copies/µL, 8.76×10-7 ng/µL, and 1×100.25 TCID50/mL, respectively. A total of 44 clinical samples were then tested using the RAA-LFD, PCR, and RT-qPCR methods. The results demonstrated a consistent detection rate between the RAA-LFD and RT-qPCR assays. Conclusion: The SVA RAA-LFD assay developed in our study exhibits excellent specificity, sensitivity, and time-saving attributes, making it ideally suited for utilization in lack-instrumented laboratory and field settings. [ABSTRACT FROM AUTHOR]

Simple Summary: Feline calicivirus (FCV) is widely prevalent in domestic cats around the world. As an RNA virus, FCV is highly mutable and prevalent. The spread of the virus mainly causes upper respiratory tract infections by low pathogenic FCV, or even, leads to death by virulent systemic FCV, which poses a serious threat to felines. Currently, there is no specific drug for this virus. Efficacious FCV vaccines protect against severe disease but not against infection. What is more, due to the variability of the ORF2 of the virus, the mutation of FCV happens at high frequencies during transportation, which result in the low cross-protection of the vaccine. And the vaccine is ineffective which can only alleviate some of the clinical symptoms, especially in some virulent systemic FCV infection cases. Consequently, there is an urgent need to develop a method that allows rapid detection of the virus for control and prevention of FCV. In this study, we designed the CRISPR/Cas13a-LFD reaction system and evaluated its specificity, sensitivity, reproducibility, and clinical reliability after establishing and optimizing, which provides an efficient tool for the early diagnosis of FCV. Feline calicivirus (FCV) is one of the most common viral pathogens in domestic cats worldwide, which mainly causes upper respiratory tract infections in felines and seriously threatens the health of felines. Consequently, it is crucial to establish a rapid detection method to efficiently take control and prevent the spread of FCV. To construct the Cas13a-RAA-LFD reaction system, this study specifically designed recombinase-aided amplification (RAA) primers added with a T7 promoter and CRISPR RNA (crRNA), which were both based on the FCV relatively conserved sequence. The Cas13a protein cleaved the reporting probes only when crRNA recognized the target sequence. The results could be directly observed by lateral flow dipsticks (LFDs). To evaluate this system, factors such as RAA amplification time, Cas13a protein concentration, crRNA concentration, and CRISPR reaction time were optimized. Then, a comparison of the coincidence rate for clinical samples between this method and the polymerase chain reaction (PCR) agarose electrophoresis method was performed to evaluate the reliability of the method. Eventually, the results indicated that the target gene could be effectively amplified by the Cas13a-RAA-LFD method, and the results could be visually observed by LFD. The method could detect FCV specifically, whilst having no cross-reaction with other common viruses which infect felines, such as feline parvovirus (FPV), feline coronavirus (FCoV) and feline herpesvirus (FHV). This method is extremely sensitive and has been validated to detect viral nucleic acids down to 100 copies/μL. The good reproducibility and stability of the method were also verified by this study. Testing of clinical samples proved that the coincidence rate of clinical detection reached 96.39%. In summary, this study established a simplistic, efficient, accurate, and visualized FCV detection method, which can be utilized for early prevention and control of FCV. [ABSTRACT FROM AUTHOR]

Simple Summary: Necrophagous insects on corpses play a crucial role in estimating the postmortem interval (PMI) through their community succession patterns and developmental data. Developing a simple, rapid, and accurate method for identifying insect species has become a key focus in forensic entomology. In this study, we collected insect samples from real crime scenes between 2018 and 2023 and identified Chrysomya megacephala (Fabricius) (Diptera: Calliphoridae) as the most frequently encountered species. To facilitate its identification, we developed a detection system using recombinase polymerase amplification (RPA) combined with lateral flow dipstick (LFD) technology. This detection system demonstrated high specificity and sensitivity and can be effectively used with rapid DNA extraction methods. Estimating the postmortem interval (PMI) is critical in the field of forensic science, and necrophagous insects play a significant role in this process. Chrysomya megacephala (Fabricius) (Diptera: Calliphoridae) is a common necrophagous insect species, making its rapid and accurate identification essential. However, commonly used molecular biology methods, such as DNA barcode, still have some limitations in identifying necrophagous insects as they are often complex, time-consuming, and reliant on laboratory instruments. Therefore, in this study, we have developed an innovative detection system for the rapid and accurate identification of C. megacephala based on the Cytochrome b gene using recombinase polymerase amplification (RPA) and lateral flow dipstick (LFD) in combination. The developed RPA-LFD detection system achieved complete amplification in just 15 min at 37 °C with good sensitivity and specificity. Only 7.8 × 10−4 ng or more of target DNA fragments were required, and a positive detection rate of 100% was achieved in 18 C. megacephala samples from actual cases. In addition, the ability of the developed RPA-LFD detection system in combination with rapid DNA extraction methods to enable on-site detection was preliminarily explored. The results suggested that when the RPA-LFD detection system was combined with the grinding ddH2O extraction method (a rapid DNA extraction method), the process from species acquisition to visualization of detection results could be completed in less than 20 min. In conclusion, this innovative RPA-LFD detection system outperforms commonly used molecular biology methods for C. megacephala identification in terms of speed, sensitivity and convenience, making it suitable for direct application at crime scenes, promising to provide important assistance in estimating PMI and expanding the impact of forensic entomological evidence. [ABSTRACT FROM AUTHOR]

Based on recombinase polymerase amplification (RPA) detection technology (combined with (lateral flow dipstick, LFD)), it is aimed to establish a dual recombinase polymerase amplification method for the rapid identification of Pasteurella multocida (Pm) and Actinobacillus pleuropneumoniae (APP). The conserved fragments of Pm kmt1 gene and APP ApxIV gene were selected for the amplification of target fragments. Eight pairs of primers for Pm and APP, and one probe for KMT1Pn and APP323Pn were designed. A single RPA-Basic primer screening test was performed. The reaction time and temperature of double RPA were optimized. The optimal primers and probe matching systems of dual RPA-LFD were explored. Dual RPA sensitivity and specificity tests were performed. The method was used to detect 60 clinical samples. The results of the primer screening test showed that the primers had the strongest specificity and the highest amplification efficiency for ApxIV2698F/ApxIV3020R and KMT1F/KMT1R. The method had the best amplification efficiency at a reaction temperature of 37ºC and a reaction time of 35 min. The optimal primer ratio of KMT1F/KMT1R and ApxIV2698F/ ApxIV3020R was 2 μL : 1.5 μL, and the optimal probe ratio of KMT1Pn and APP323Pn was 0.6 μL : 0.4 μL. The minimum detection limit of dual RPA-Basic and RPA-LFD sensitivity test was 10-6 ng/μL. The specific test results showed no cross-reaction with enteropathogenic Escherichia coli, Salmonella, Glaesserella parasuis, Staphylococcus aureus, Streptococcus suis, Aeromonas hydrophila. Using 60 clinical samples of suspected Pm and/or APP infection to evaluate the detection system, the detection rate of dual RPA-Basic and RPA-LFD is higher than that of PCR, indicating that they have strong practicability. This study successfully established a dual RPA-Basic and RPA-LFD detection method for Pm and APP, which can be used for the rapid differential diagnosis of Pm and APP mixed infection in clinical.

Abstract Background Porcine teschovirus (PTV) is an important enteropathogen, associated with symptoms of polioencephalomyelitis, pneumonia, pericarditis, myocarditis, diarrhea, and reproductive disorders in pigs. Rapid and precise diagnostic methods are essential for managing PTV infections. The study introduced a simple, quick, and visual approach for detecting PTV through the use of RT-RAA coupled with LFD. Results The procedures of RT-RAA-LFD for PTV could be carried out with 1.0 μmol/L primer concentration and 2.0 μmol/L probe concentration at 37 °C for 20 min, and the amplification result could be visualized within 5 min through LFD detection. Meanwhile, the assay established in this study showed no interaction with other associated diarrhea viruses, and has high specificity to PTV, with a minimal detection limit of 10 copies/μL and good repeatability. 128 clinical samples suspected of having a PTV infection were tested by RT-PCR and RT-RAA-LFD, respectively. The total diagnostic coincidence rate was 98.44% (126/128) with a Kappa value of 0.96(K ≥ 0.75), demonstrating a high degree of agreement to detect PTV for the two methods. Conclusions The RT-RAA-LFD assay created in this research displayed quick response, specificity, and sensitivity, capable of successfully detecting PTV in less than 25 min, providing an easy-to-use diagnostic instrument for rapid and visual PTV detection, especially suitable for labs and low-resource environments.

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.

Abstract Background Globally, around 7 to 20 million people are believed to be suffering from coinfection with both hepatitis B virus (HBV) and hepatitis C virus (HCV). The loop-mediated isothermal amplification (LAMP) approach, introduced by Notomi and colleagues, has undergone substantial advancements as an effective molecular tool that enables the simultaneous analysis of multiple samples in a single tube. Methods The present study examined the simultaneous detection of HBV and HCV in a single tube using melt curve analysis multiplex LAMP (mLAMP), which is based on the identification of unique melting peak temperatures. Selected regions for primer design including the S gene of HBV and the UTR gene of HCV. Primer optimization is initially performed through individual HBV and HCV LAMP analysis. Following the optimization process, the mLAMP assay was evaluated by optimizing the multiplex reaction mixture, determining the reaction time, and analyzing the limit of detection (LOD). The results are also analyzed using lateral flow dipsticks (LFD), which enable the visual detection of HBV and HCV by adding 20 pmol FITC-labeled LF primers into the reaction mixture prior the mLAMP. Results The LOD for the mLAMP assay was determined as 10 copies/µl, and no cross-reactivity with other microorganisms was detected. The detection results obtained from patient plasma were also visually demonstrated using LFD, and displayed significant concordance with those obtained from Real-Time Polymerase Chain Assay. The mLAMP assay revealed a diagnostic sensitivity of 95% for detecting the HBV, and LOD is 90% for HCV. The overall diagnostic sensitivity of the mLAMP assay for both viruses was 85%. The assay confirmed a specificity of 100%. Conclusion The mLAMP assay displays significant promise for analyzing coinfected samples by simultaneously detecting the dual targets HBV and HCV within a set temperature of 62 °C, all within a time frame of 1 h. Additionally, when paired with disposable LFD, the mLAMP assay enables rapid visual detection of assay results in a matter of minutes. The result contributes to the mLAMP assay being highly suitable for coinfection screening, particularly in field conditions.

Avian leukemia virus (ALV) is one of the main pathogens of poultry tumor diseases, and has caused significant economic losses to the poultry industry since its discovery. Therefore, establishing a rapid detection method is essential to effectively prevent and control the spread of ALV. In this study, specific CRISPR RNA (crRNA) and recombinase-aided amplification (RAA) primers with T7 promoter were designed based on the relatively conserved sequence of avian leukemia virus. When crRNA recognized the target sequence, Cas13a protein was activated to cut the reporting probes, and then the detection results were read by using lateral flow dipstick (LFD). The RAA-CRISPR/Cas13a-LFD reaction system was constructed. The RAA amplification time, Cas13a protein concentration, crRNA concentration and CRISPR reaction time were optimized to evaluate the specificity, sensitivity and reproducibility of the system. Finally, RAA-CRISPR/Cas13a-LFD method was compared with Polymerase chain reaction (PCR)-Agarose electrophoresis method and qPCR method in the detection of clinical samples, and the reliability of RAA-CRISPR/Cas13a-LFD method was evaluated. The results showed that the RAA-CRISPR/Cas13a-LFD method could effectively amplify the target gene at 37°C for 40 min, and the test results could be determined by LFD visual observation. The method had good specificity and no cross-reaction with Marek's disease virus (MDV), Fowl adenovirus (FAdV), Infectious bursal disease virus (IBDV), Newcastle disease virus (NDV), Infectious laryngotracheitis virus (ILTV), and Infectious bronchitis virus (IBV). The minimum detection limit of the method was 100 copies/μL, and it had good repeatability and stability. The coincidence rate of clinical detection reached 97.69% and 99.23%. In summary, this study established a simple, efficient, accurate and visualized ALV detection method, which can be used for the prevention and rapid clinical diagnosis of avian leukosis (AL). [ABSTRACT FROM AUTHOR]

Background: Globally, around 7 to 20 million people are believed to be suffering from coinfection with both hepatitis B virus (HBV) and hepatitis C virus (HCV). The loop-mediated isothermal amplification (LAMP) approach, introduced by Notomi and colleagues, has undergone substantial advancements as an effective molecular tool that enables the simultaneous analysis of multiple samples in a single tube. Methods: The present study examined the simultaneous detection of HBV and HCV in a single tube using melt curve analysis multiplex LAMP (mLAMP), which is based on the identification of unique melting peak temperatures. Selected regions for primer design including the S gene of HBV and the UTR gene of HCV. Primer optimization is initially performed through individual HBV and HCV LAMP analysis. Following the optimization process, the mLAMP assay was evaluated by optimizing the multiplex reaction mixture, determining the reaction time, and analyzing the limit of detection (LOD). The results are also analyzed using lateral flow dipsticks (LFD), which enable the visual detection of HBV and HCV by adding 20 pmol FITC-labeled LF primers into the reaction mixture prior the mLAMP. Results: The LOD for the mLAMP assay was determined as 10 copies/µl, and no cross-reactivity with other microorganisms was detected. The detection results obtained from patient plasma were also visually demonstrated using LFD, and displayed significant concordance with those obtained from Real-Time Polymerase Chain Assay. The mLAMP assay revealed a diagnostic sensitivity of 95% for detecting the HBV, and LOD is 90% for HCV. The overall diagnostic sensitivity of the mLAMP assay for both viruses was 85%. The assay confirmed a specificity of 100%. Conclusion: The mLAMP assay displays significant promise for analyzing coinfected samples by simultaneously detecting the dual targets HBV and HCV within a set temperature of 62 °C, all within a time frame of 1 h. Additionally, when paired with disposable LFD, the mLAMP assay enables rapid visual detection of assay results in a matter of minutes. The result contributes to the mLAMP assay being highly suitable for coinfection screening, particularly in field conditions. [ABSTRACT FROM AUTHOR]

Acidovorax citrulli (Ac) is an important pathogenic bacterium causing bacterial fruit blotch (BFB) in Cucurbitaceae plants and is an important quarantine pest in China. This study was conducted to establish a rapid, convenient, and accurate visual method for detecting A. citrulli. A. citrulli-specific primers and a prober were designed based on the conserved region of the YD-repeat protein gene. Loop-mediated isothermal amplification combined with lateral flow dipstick (LAMP-LFD) was used to establish an assay for the rapid visual detection of A. citrulli by optimizing the reaction temperature and time. The specificity, sensitivity, and performance of the optimized LAMP-LFD assay were evaluated using the genomic DNA of the tested isolates, A. citrulli pure culture, infested seeds, commercial seeds, and leaf samples. The optimal assay temperature and time were 64 °C and 60 min, respectively. The assay specifically detected A. citrulli, and no cross-reactions were observed with the genomic DNA of other closely related species. The detection sensitivity of the LAMP-LFD for detecting pure genomic DNA, the bacterial suspension, bacterial amount on seeds (colony-forming units (CFU)·g−1), and infection rate of seeds (%) were 1 fg·μL−1, 8 CFU·mL−1, 5 CFU·g−1, and 0.05% infestation per reaction, respectively. The positive detection rate of the LAMP-LFD assay was 20–100% in seed samples (n = 1000 seeds) with 0.05–0.1% infestation. The LAMP-LFD assay rapidly and accurately detected A. citrulli in seeds and leaf tissues carrying pathogens. This assay thus offers the advantages of easy operation, rapidity, high specificity and sensitivity, low cost (no need for complex and expensive precision instruments), visualization of detection results, good stability, and strong applicability, which can be used for epidemiological studies and disease management. [ABSTRACT FROM AUTHOR]

Abstract Background Avian influenza virus (AIV) not only causes huge economic losses to the poultry industry, but also threatens human health. Reverse transcription recombinase-aided amplification (RT-RAA) is a novel isothermal nucleic acid amplification technology. This study aimed to improve the detection efficiency of H5, H7, and H9 subtypes of AIV and detect the disease in time. This study established RT-RAA-LFD and real-time fluorescence RT-RAA (RF-RT-RAA) detection methods, which combined RT-RAA with lateral flow dipstick (LFD) and exo probe respectively, while primers and probes were designed based on the reaction principle of RT-RAA. Results The results showed that RT-RAA-LFD could specifically amplify H5, H7, and H9 subtypes of AIV at 37 °C, 18 min, 39 °C, 20 min, and 38 °C, 18 min, respectively. The sensitivity of all three subtypes for RT-RAA-LFD was 102 copies/µL, which was 10 ∼100 times higher than that of reverse transcription polymerase chain reaction (RT-PCR) agarose electrophoresis method. RF-RT-RAA could specifically amplify H5, H7, and H9 subtypes of AIV at 40 °C, 20 min, 38 °C, 16 min, and 39 °C, 17 min, respectively. The sensitivity of all three subtypes for RF-RT-RAA was 101 copies/µL, which was consistent with the results of real-time fluorescence quantification RT-PCR, and 100 ∼1000 times higher than that of RT-PCR-agarose electrophoresis method. The total coincidence rate of the two methods and RT-PCR-agarose electrophoresis in the detection of clinical samples was higher than 95%. Conclusions RT-RAA-LFD and RF-RT-RAA were successfully established in this experiment, with quick response, simple operation, strong specificity, high sensitivity, good repeatability, and stability. They are suitable for the early and rapid diagnosis of Avian influenza and they have positive significance for the prevention, control of the disease, and public health safety.

[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]

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]

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]

The infection of Bombyx mori nucleopolyhedrovirus (BmNPV) is one of the main causes of economic losses in sericulture. Thus, it is essential to establish rapid and effective method for BmNPV detection. In the present study, we have developed a recombinase-aided amplification (RAA) to amplify the BmNPV genomic DNA at 37 °C within 30 min, and achieved a rapid detection method by coupling with a lateral flow dipstick (LFD). The RAA-LFD method had a satisfactory detection limit of 6 copies/μL of recombinant plasmid pMD19-T-IE1, and BmNPV infection of silkworm can be detected 12 h post-infection. This method was highly specific for BmNPV, and without cross-reactivity to other silkworm pathogens. In contrast to conventional polymerase chain reaction (PCR), the RAA-LFD assay showed higher sensitivity, cost-saving, and especially is apt to on-site detection of BmNPV infection in the sericulture production. [ABSTRACT FROM AUTHOR]

Blastocystis spp. is a ubiquitous protozoon in the intestinal tract of human and many animals. Microscopic examination is the main method of clinical diagnosis for Blastocystis spp., which is prone to false negative. A simple and rapid diagnosis of Blastocystis spp. infection is an important step to prevent and control blastocystosis. Here, a recombinase polymerase amplification-lateral flow dipstick (RPA-LFD) assay was developed for rapid visual detection of Blastocystis spp. DNA amplification could be performed within 18 min at 37°C. The minimum DNA detection limit was 1 µg/mL, and there was no cross-reactivity with 12 other non-target pathogens, which was consistent with the sensitivity of conventional PCR (cPCR). Furthermore, 56 fecal samples from the Third Affiliated Hospital of Xinxiang Medical University were tested using RPA and cPCR methods respectively, and the results were completely consistent. The results show that RPA-LFD method has high accuracy and visual results, which provides a new choice for the differential diagnosis and rapid field detection of Blastocystis spp. [ABSTRACT FROM AUTHOR]

Background: Avian influenza virus (AIV) not only causes huge economic losses to the poultry industry, but also threatens human health. Reverse transcription recombinase-aided amplification (RT-RAA) is a novel isothermal nucleic acid amplification technology. This study aimed to improve the detection efficiency of H5, H7, and H9 subtypes of AIV and detect the disease in time. This study established RT-RAA-LFD and real-time fluorescence RT-RAA (RF-RT-RAA) detection methods, which combined RT-RAA with lateral flow dipstick (LFD) and exo probe respectively, while primers and probes were designed based on the reaction principle of RT-RAA. Results: The results showed that RT-RAA-LFD could specifically amplify H5, H7, and H9 subtypes of AIV at 37 °C, 18 min, 39 °C, 20 min, and 38 °C, 18 min, respectively. The sensitivity of all three subtypes for RT-RAA-LFD was 102 copies/µL, which was 10 ∼100 times higher than that of reverse transcription polymerase chain reaction (RT-PCR) agarose electrophoresis method. RF-RT-RAA could specifically amplify H5, H7, and H9 subtypes of AIV at 40 °C, 20 min, 38 °C, 16 min, and 39 °C, 17 min, respectively. The sensitivity of all three subtypes for RF-RT-RAA was 101 copies/µL, which was consistent with the results of real-time fluorescence quantification RT-PCR, and 100 ∼1000 times higher than that of RT-PCR-agarose electrophoresis method. The total coincidence rate of the two methods and RT-PCR-agarose electrophoresis in the detection of clinical samples was higher than 95%. Conclusions: RT-RAA-LFD and RF-RT-RAA were successfully established in this experiment, with quick response, simple operation, strong specificity, high sensitivity, good repeatability, and stability. They are suitable for the early and rapid diagnosis of Avian influenza and they have positive significance for the prevention, control of the disease, and public health safety. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Preventive Veterinary Medicine / Zhongguo Yufang Shouyi Xuebao is the property of Chinese Journal of Preventive Veterinary Medicine Editorial Office 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.)

Simple Summary: Duck hepatitis B virus was originally found in newly hatched Pekin ducks in the United States in 1980, which was followed by global spread and expansion to geese; thus, the virus may cause more financial damage to the poultry industry worldwide. In this study, an assay combining multienzyme isothermal rapid amplification (MIRA) and lateral flow dipstick (LFD) was developed for the efficient and rapid detection of DHBV. Followed by optimization testing of the reaction temperature and duration, the complete procedure for the newly developed MIRA assay for DHBV detection could be carried out by only using a water bath and only required 15 min. The newly developed MIRA assay was only confirmed to work with DHBV, had a 10 times higher sensitivity than the routine polymerase chain reaction (PCR) assay, and displayed better practicability for clinical samples. In line with these results, it was determined that the novel MIRA assay combined with LFD developed in this study would be a good alternative approach for DHBV detection in field clinics. Duck hepatitis B virus (DHBV) is widely prevalent in global ducks and has been identified in Chinese geese with a high prevalence; the available detection techniques are time-consuming and require sophisticated equipment. In this study, an assay combining multienzyme isothermal rapid amplification (MIRA) and lateral flow dipstick (LFD) was developed for the efficient and rapid detection of DHBV. The primary reaction condition of the MIRA assay for DHBV detection was 10 min at 38 °C without a temperature cycler. Combined with the LFD assay, the complete procedure of the newly developed MIRA assay for DHBV detection required only 15 min, which is about one-fourth of the reaction time for routine polymerase chain reaction assay. And electrophoresis and gel imaging equipment were not required for detection and to read the results. Furthermore, the detection limit of MIRA was 45.6 copies per reaction, which is approximately 10 times lower than that of a routine polymerase chain reaction assay. The primer set and probe had much simpler designs than loop-mediated isothermal amplification, and they were only specific to DHBV, with no cross-reactivity with duck hepatitis A virus subtype 1 and duck hepatitis A virus subtype 3, goose parvovirus, duck enteritis virus, duck circovirus, or Riemerella anatipestifer. In this study, we offer a simple, fast, and accurate assay method to identify DHBV in clinical serum samples of ducks and geese, which would be suitable for widespread application in field clinics. [ABSTRACT FROM AUTHOR]

In order to establish a rapid detection method for Aeromonas hydrophila utilizing recombinase polymerase amplification (RPA) technology, we designed specific RPA primers based on the conserved sequence of the gyrB gene of Aeromonas hydrophila. The research included the optimization of reaction conditions and an assessment of specificity and sensitivity by both agarose gel electrophoresis (AGE) and lateral flow dipstick (LFD) chromatography. The experimental results showed that the established rapid detection for Aeromonas hydrophila could detect Aeromonas hydrophila within 30min at the optimal temperature of 38°C. The minimum limit of detection (LOD) for Aeromonas hydrophila pure culture and genomic DNA using the RPA-LFD method was determined to be 10³ cfu/mL and 100 pg/μL, respectively. Furthermore, the simultaneous detection of clinical samples from hybridized sturgeon, treated using our established RPA-LFD method, exhibited consistent results when compared to conventional PCR. In conclusion, the recombinase polymerase amplification combined with lateral flow test strip (RPA-LFD) method of Aeromonas hydrophila was successfully established by exploring and optimizing RPA reaction conditions. The method was characterized by its simplicity, rapid reaction time, and lack of reliance on expensive instrumenttion compared with conventional PCR. Importantly, this method provides effective technical support for the early diagnosis of sturgeon suffering from bacterial diseases caused by Aeromonas hydrophila in the future. [ABSTRACT FROM AUTHOR]

BackgroundSenecavirus A (SVA) is a newly pathogenic virus correlated with the acute death of piglets and vesicular lesions in pigs. The further prevalence of SVA will cause considerable economic damage to the global pig farming industry. Therefore, rapid and accurate diagnostic tools for SVA are crucial for preventing and controlling the disease.MethodsWe designed multiple primer pairs targeting the most conserved region of the SVA 3D gene and selected those with the highest specificity. Nfo-probes were subsequently developed based on the highest specificity primer pairs. Subsequently, the recombinase-assisted amplification (RAA) reaction was completed, and the reaction temperature and duration were optimized. The RAA amplicons were detected using a lateral flow device (LFD). Finally, a rapid and intuitive RAA-LFD assay was established against SVA.ResultsThe SVA RAA-LFD assay can be performed under reaction conditions of 35°C within 17 minutes, with results observable to the naked eye. We then evaluated the performance of this method. It exhibited high specificity and no cross-reaction with the other common swine pathogens. The lowest detectable limits of this method for the plasmid of pMD18-SVA-3D, DNA amplification product, and viral were 3.86×101 copies/µL, 8.76×10-7 ng/µL, and 1×100.25 TCID50/mL, respectively. A total of 44 clinical samples were then tested using the RAA-LFD, PCR, and RT-qPCR methods. The results demonstrated a consistent detection rate between the RAA-LFD and RT-qPCR assays.ConclusionThe SVA RAA-LFD assay developed in our study exhibits excellent specificity, sensitivity, and time-saving attributes, making it ideally suited for utilization in lack-instrumented laboratory and field settings.

Purpose: To address the issue that laboratory methods cannot meet the need foron-site rapid testingat the grassroot level, a quick method for detecting the authenticity of meat products was established based on multienzyme isothermal rapid amplification (MIRA) coupled with lateral flow dipstick (LFD). Methods: Pig, cattle, sheep, chicken, and duck-specific mitochondrial gene sequences were selected through GenBank, and intra-species conserved and inter-species specific target fragments were compared using the DNAStar Megalign software. According to the design principles of MIRA primers and probes, target gene-specific primer and probe sets were designed and screened systematically through positive, negative and blank controls to determine the species-specific primers and probes. The reaction system, temperature, and time were optimized. Analytical figures of merit of the method including DNA extraction, sensitivity, detection limit, false positive rate and false negative rate were evaluated to verify its validity. Results: Compared with real-time fluorescent polymerase chain reaction (PCR), the average false positive rate of this method was 3.49%, and the false negative rate was 3.54%, which meets the requirements of on-site rapid testing. Conclusion: In this study, the MIRA-LFD technique was established for 5 common meats, namely, cattle, sheep, pig, chicken and duck, and its validity and feasibility were confirmed, realizing on-site rapid testing of the authenticity of meat products.

Feline calicivirus (FCV) is one of the most common viral pathogens in domestic cats worldwide, which mainly causes upper respiratory tract infections in felines and seriously threatens the health of felines. Consequently, it is crucial to establish a rapid detection method to efficiently take control and prevent the spread of FCV. To construct the Cas13a-RAA-LFD reaction system, this study specifically designed recombinase-aided amplification (RAA) primers added with a T7 promoter and CRISPR RNA (crRNA), which were both based on the FCV relatively conserved sequence. The Cas13a protein cleaved the reporting probes only when crRNA recognized the target sequence. The results could be directly observed by lateral flow dipsticks (LFDs). To evaluate this system, factors such as RAA amplification time, Cas13a protein concentration, crRNA concentration, and CRISPR reaction time were optimized. Then, a comparison of the coincidence rate for clinical samples between this method and the polymerase chain reaction (PCR) agarose electrophoresis method was performed to evaluate the reliability of the method. Eventually, the results indicated that the target gene could be effectively amplified by the Cas13a-RAA-LFD method, and the results could be visually observed by LFD. The method could detect FCV specifically, whilst having no cross-reaction with other common viruses which infect felines, such as feline parvovirus (FPV), feline coronavirus (FCoV) and feline herpesvirus (FHV). This method is extremely sensitive and has been validated to detect viral nucleic acids down to 100 copies/μL. The good reproducibility and stability of the method were also verified by this study. Testing of clinical samples proved that the coincidence rate of clinical detection reached 96.39%. In summary, this study established a simplistic, efficient, accurate, and visualized FCV detection method, which can be utilized for early prevention and control of FCV.

Estimating the postmortem interval (PMI) is critical in the field of forensic science, and necrophagous insects play a significant role in this process. Chrysomya megacephala (Fabricius) (Diptera: Calliphoridae) is a common necrophagous insect species, making its rapid and accurate identification essential. However, commonly used molecular biology methods, such as DNA barcode, still have some limitations in identifying necrophagous insects as they are often complex, time-consuming, and reliant on laboratory instruments. Therefore, in this study, we have developed an innovative detection system for the rapid and accurate identification of C. megacephala based on the Cytochrome b gene using recombinase polymerase amplification (RPA) and lateral flow dipstick (LFD) in combination. The developed RPA-LFD detection system achieved complete amplification in just 15 min at 37 °C with good sensitivity and specificity. Only 7.8 × 10−4 ng or more of target DNA fragments were required, and a positive detection rate of 100% was achieved in 18 C. megacephala samples from actual cases. In addition, the ability of the developed RPA-LFD detection system in combination with rapid DNA extraction methods to enable on-site detection was preliminarily explored. The results suggested that when the RPA-LFD detection system was combined with the grinding ddH2O extraction method (a rapid DNA extraction method), the process from species acquisition to visualization of detection results could be completed in less than 20 min. In conclusion, this innovative RPA-LFD detection system outperforms commonly used molecular biology methods for C. megacephala identification in terms of speed, sensitivity and convenience, making it suitable for direct application at crime scenes, promising to provide important assistance in estimating PMI and expanding the impact of forensic entomological evidence.

Copyright of Shipin Kexue/ Food Science is the property of Food Science 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.)

Bovine Viral Diarrhea Virus (BVDV) and Infectious Bovine Rhinotracheitis Virus (IBRV) are the two most prevalent infectious diseases in cattle. They both can cause persistent infection and immunosuppression, resulting in significant economic losses in the livestock industry. Therefore, rapid detection of early BVDV and IBRV infections is crucial. In this study, a method for the rapid detection of BVDV and IBRV was established by using recombinase polymerase amplification (RPA) combined with lateral flow device (LFD). By optimizing the temperature and time conditions of the RPA reaction, the sensitivity, specificity, and clinical performance were evaluated. The results indicated that the RPA reaction could be completed at 40◦C within 25min. The LOD for BVDV and IBRV by RPA-LFD were 5.1 × 10¹ copies/μL and 6.65 × 10¹ copies/μL, respectively, with no cross-reactivity observed with other viruses such as CSFV, BRSV, BPIV3, BRV, and BCoV. Testing of 32 clinical samples showed consistent results between RPA-LFD and qPCR. The RPA-LFD method established in this study can be used for the rapid clinical detection of BVDV and IBRV, which providing a rapid and convenient molecular biology approach for on-site rapid detection and epidemiological investigations. Simultaneously, it offers technical support for the prevention and control of these viruses. [ABSTRACT FROM AUTHOR]

Vibrio alginolyticus (V. alginolyticus) is a common pathogen in the ocean. In addition to causing serious economic losses in aquaculture, it can also infect humans. The rapid detection of nucleic acids of V. alginolyticus with high sensitivity and specificity in the field is very important for the diagnosis and treatment of infection caused by V. alginolyticus. Here, we established a simple, fast and effective molecular method for the identification of V. alginolyticus that does not rely on expensive instruments and professionals. The method integrates recombinase polymerase amplification (RPA) technology with CRISPR system in a single PCR tube. Using this method, the results can be visualized by lateral flow dipstick (LFD) in less than 50 min, we named this method RPA-CRISPR/Cas13a-LFD. The method was confirmed to achieve high specificity for the detection of V. alginolyticus with no cross-reactivity with similar Vibrio and common clinical pathogens. This diagnostic method shows high sensitivity; the detection limit of the RPA-CRISPR/Cas13a-LFD is 10 copies/µL. We successfully identified 35 V. alginolyticus strains from a total of 55 different bacterial isolates and confirmed their identity by (Matrix-assisted laser desorption ionization time-of-flight mass spectrometry, MALDI-TOF MS). We also applied this method on infected mice blood, and the results were both easily and rapidly obtained. In conclusion, RPA-CRISPR/Cas13a-LFD offers great potential as a useful tool for reliable and rapid diagnosis of V. alginolyticus infection, especially in limited conditions. [ABSTRACT FROM AUTHOR]

Acidovorax citrulli (Ac) is an important pathogenic bacterium causing bacterial fruit blotch (BFB) in Cucurbitaceae plants and is an important quarantine pest in China. This study was conducted to establish a rapid, convenient, and accurate visual method for detecting A. citrulli. A. citrulli-specific primers and a prober were designed based on the conserved region of the YD-repeat protein gene. Loop-mediated isothermal amplification combined with lateral flow dipstick (LAMP-LFD) was used to establish an assay for the rapid visual detection of A. citrulli by optimizing the reaction temperature and time. The specificity, sensitivity, and performance of the optimized LAMP-LFD assay were evaluated using the genomic DNA of the tested isolates, A. citrulli pure culture, infested seeds, commercial seeds, and leaf samples. The optimal assay temperature and time were 64 °C and 60 min, respectively. The assay specifically detected A. citrulli, and no cross-reactions were observed with the genomic DNA of other closely related species. The detection sensitivity of the LAMP-LFD for detecting pure genomic DNA, the bacterial suspension, bacterial amount on seeds (colony-forming units (CFU)·g−1), and infection rate of seeds (%) were 1 fg·μL−1, 8 CFU·mL−1, 5 CFU·g−1, and 0.05% infestation per reaction, respectively. The positive detection rate of the LAMP-LFD assay was 20–100% in seed samples (n = 1000 seeds) with 0.05–0.1% infestation. The LAMP-LFD assay rapidly and accurately detected A. citrulli in seeds and leaf tissues carrying pathogens. This assay thus offers the advantages of easy operation, rapidity, high specificity and sensitivity, low cost (no need for complex and expensive precision instruments), visualization of detection results, good stability, and strong applicability, which can be used for epidemiological studies and disease management.

Objective: To develop a rapid, efficient and visual method for the detection of bacterial colistin resistance gene mcr-1, so as to provide the basis and convenience for the development of its detection at the grassroots level. Methods: Using recombinase polymerase amplification combined with a lateral flow dipstick (RPA-LFD) assay, supplemented by a hand-held colloidal gold reader. According to the conserved sequence of the mcr-1 gene, a pair of specific RPA primers were designed and synthesized. Through the optimization of the reaction conditions and system, as well as the specificity test, sensitivity test, simulated food sample test and actual sample test, the RPA-LFD assay for visual and quantitative detection of bacterial colistin resistance gene mcr-1 was successfully established. Results: When the primer concentration was 400 nmol/L and the primer ratio was 1:1, the optimal reaction conditions of this method are Mg2+ concentration 14.0 mmol/L, reaction temperature 37 ℃ and reaction time 20 min. The sensitivity was good, the standard curve equation was y=0.117x+0.051, the quantification limit was 101~108 copies/μL, and the detection limit was 101 copies/μL, which was an order of magnitude lower than the PCR method and the detection result of the simulated sample was consistent with the PCR method. Carrying status of colistin resistance gene mcr-1 in each 15 pork samples, chicken samples, pig farm environmental samples, broiler farm environmental samples, Escherichia coli isolates and Enterobacter campylobacter isolates were analyzed by the established RPA-LFD assay. The detection rate of positive samples by RPA-LFD assay was consistent with that of conventional PCR method, and a total of 9 mcr-1 gene positive samples were detected. RPA-LFD quantitative analysis showed that the concentration of mcr-1 gene in positive samples was between 4.5×102~8.6×104 copies/µL. Conclition: The RPA-LFD detection method of the bacterial colistin resistance gene mcr-1 established in this study had strong specificity, high sensitivity, and simple operation, and could be widely used in grassroots inspections.

Anisakiasis is a food-borne parasitic disease mainly caused by the third stage of Anisakis simplex (s. s.) and Anisakis pegreffii. Traditional methods for detecting of Anisakis involve morphology identification such as visual inspection, enzyme digestion, and molecular methods based on PCR, but they have certain limitations. In this study, the internal transcribed spacer 1 (ITS 1) regions of Anisakis were targeted to develop a visual screening method for detecting A. simplex (s. s.) and A. pegreffii in fish meat based on recombinase polymerase amplification (RPA) combined with lateral flow dipstick (LFD). Specific primers and probes were designed and optimized for temperature, reaction time, and detection threshold. LFD produced clear visual results that were easily identifiable after a consistent incubation of 10–20 min at 37 °C. The whole process of DNA amplification by RPA and readout by LFD did not exceed 30 min. In addition, the detection limit is up to 9.5 × 10−4 ng/μL, and the detection of the artificially contaminated samples showed that the developed assay can effectively and specifically detect A. simplex (s. s.) and A. pegreffii, which fully meet the market's requirements for fish food safety supervision.

Introduction:Salmonella was one of the most common bacteria that caused foodborne illness, with S. typhimurium (Salmonella typhimurium) and S. enteritidis (Salmonella enteritidis) infections accounting for more than 75% of human salmonella infections.Methods: In this study, we developed a method of dual recombinase polymerase amplification (RPA) combined with a lateral flow dipstick for the rapid detection of S. typhimurium and S. enteritidis in clinical specimens (stool).Results: The entire reaction process, including amplification and result reading, could be completed within 65 min. The detection limits of S. typhimurium and S. enteritidis in pure culture samples were 5.23 × 101 CFU/mL and 3.59 × 101 CFU/mL, respectively. The detection limits of S. typhimurium and S. enteritidis in artificially contaminated samples were 8.30 × 101 CFU/mL and 2.70 × 102 CFU/mL, respectively. In addition, the method had no cross-reaction with other pathogenic microorganisms. The results in clinical samples were fully consistent with those obtained using Bacterial Analysis Manual, with sensitivity and specificity were 100% (8/8) and 100% (17/17) for S. typhimurium and 100% (4/4) and 100% (21/21) for S. enteritidis, respectively.Discussion: The detection limits of S. typhimurium and S. enteritidis in artificially contaminated samples were higher than those in pure culture samples, which might be attributed to the inherent complex composition of artificially contaminated samples. In addition, the detection limits of S. typhimurium and S. enteritidis in the same sample were also different, which might be attributed to different amplification efficiency of two target genes in the same reaction system.Conclusion: This assay had potential application outdoors, as it could be performed within 1 h at 38°C without a complex instrument, and the results could be observed with the naked eye. In conclusion, the dual RPA-LFD assay established in this study had practical significance for the rapid detection of S. typhimurium and S. enteritidis in the future.

To rapidly, specifically, and sensitively detect avian influenza virus (AIV), this research established a visual detection method of recombinase-aided amplification (RAA) based on Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) and CRISPR associated proteins 13a (Casl3a) system. In this study, specific primers and CRISPR RNA (crRNA) were designed according to the conservative sequence of AIV Nucleprotein (NP) gene. RAA technology was used to amplify the target sequence, and the amplification products were visually detected by lateral flow dipstick (LFD). The specificity, sensitivity, and reproducibility of RAA-CRISPR-Casl3a-LFD were evaluated. At the same time, this method and polymerase chain reaction (PCR)-agarose electrophoresis method were used to detect clinical samples, and the coincidence rate of the two detection methods was calculated. The results showed that the RAA-CRISPR-Casl3a-LFD method could achieve specific amplification of the target gene fragments, and the detection results could be visually observed through the LFD. Meanwhile, there was no cross-reaction with infectious bronchitis virus (IBV), infectious laryngotracheitis virus (ILTV), and Newcastle disease virus (NDV). The sensitivity reached 10º copies/µL, which was 1,000-fold higher than that of PCR-agarose electrophoresis method. The coincidence rate of clinical tests was 98.75 %, and the total reaction time was ~1h. The RAA-CRISPR-Cas13a-LFD method established in this study had the advantages of rapid, simple, strong specificity, and high sensitivity, which provided a new visual method for AIV detection. [ABSTRACT FROM AUTHOR]

The harmful algal bloom (HAB) species Pseudo-nitzschia multiseries is widely distributed worldwide and is known to produce the neurotoxin domoic acid, which harms marine wildlife and humans. Early detection and preventative measures are more critical than late management. However, the major challenge related to early detection is the accurate and sensitive detection of microalgae present in low abundance. Therefore, developing a sensitive and specific method that can rapidly detect P. multiseries is critical for expediting the monitoring and prediction of HABs. In this study, a novel assay method, recombinase polymerase amplification combined with lateral flow dipstick (RPA-LFD), is first developed for the detection of P. multiseries. To obtain the best test results, several important factors that affected the amplification effect were optimized. The internal transcribed spacer sequence of the nuclear ribosomal DNA from P. multiseries was selected as the target region. The results showed that the optimal amplification temperature and time for the recombinase polymerase amplification (RPA) of P. multiseries were 37 °C and 15 min. The RPA products could be visualized directly using the lateral flow dipstick after only 3 min. The RPA-LFD assay sensitivity for detection of recombinant plasmid DNA (1.9 × 100 pg/μL) was 100 times more sensitive than that of RPA, and the RPA-LFD assay sensitivity for detection of genomic DNA (2.0 × 102 pg/μL) was 10 times more sensitive than that of RPA. Its feasibility in the detection of environmental samples was also verified. In conclusion, these results indicated that the RPA-LFD detection of P. multiseries that was established in this study has high efficiency, sensitivity, specificity, and practicability. Management measures made based on information gained from early detection methods may be able to prevent certain blooms. The use of a highly sensitive approach for early warning detection of P. multiseries is essential to alleviate the harmful impacts of HABs on the environment, aquaculture, and human health. [ABSTRACT FROM AUTHOR]

Due to its high mortality rate, highly pathogenic avian influenza (HPAI), a notifiable animal illness designated by the World Organisation for Animal Health (WOAH), has caused enormous financial losses to the poultry sector. The H5 subtype of avian influenza virus (H5-AIV) is regarded as the most common highly pathogenic avian influenza virus (HPAIV) that threatens public health and safety. Virus isolation and reverse transcription quantitative PCR (RT-qPCR) are usually used to detect H5- AIV and are important for the timely diagnosis and control of H5-AIV. However, these methods are time-consuming and require a significant amount of effort. In this study, we established a recombinase-aided amplification (RAA) combined with CRISPR-Cas13a and lateral flow dipstick (LFD) assay for the detection of H5- AIV. The results showed that the process can be completed within 40 min at 37°C. The method had a detection limit of 0.1 copy/μL, which was comparable to the RT-qPCR. There was no cross-reactivity with H3-AIV, H7-AIV, H9-AIV, H10- AIV, IBV, NDV, RVA and DAstV. The kappa value of RT-RAA-Cas13a-LFD and RTqPCR in 380 clinical samples was 0.89 (κ>0.75). In conclusion, we established a convenient, efficient and accurate method to detect H5-AIV, and the results can be visualized and interpreted using LFD, which can be adapted to the needs of grassroots laboratories and field-deployable assays. This approach provides a new perspective for clinical H5-AIV diagnosis and has great potential for application in clinical quarantine of the poultry farming. [ABSTRACT FROM AUTHOR]

Agrilus mali stands as a significant wood-boring pest prevalent in Northeast Asia. Identifying this pest beetle is often hindered by insufficient efficient, rapid, on-site discrimination methods beyond examining adult morphological features. As a result, an urgent need arises for developing and implementing a rapid and accurate molecular technique to distinguish and manage the beetle. This study presents a straightforward, swift, highly specific, and sensitive method built upon recombinase polymerase amplification combined with a lateral flow dipstick (RPA-LFD). This method demonstrates the capability to promptly identify the beetle, even during its larval stage. RPA primers and probes were designed using the internal transcribed spacer 1 region. Through probe optimization, false-positive signals were successfully eliminated, with an accompanying discussion on the underlying causes of such signals. The RPA-LFD assays exhibited remarkable specificity and sensitivity, requiring as little as 10−3 ng of purified DNA. Furthermore, the extraction of crude DNA was achieved through immersion in sterile distilled water, thus streamlining the assay process. Achievable at temperatures ranging from 30 to 50 °C, the RPA-LFD assay can be executed manually without specialized equipment. By merging the RPA-LFD assay with DNA coarse extraction, A. mali can be detected within just 30 min. This current study effectively demonstrates the immense potential of RPA-LFD in quarantine and pest management. Additionally, it presents a universal technique for the rapid on-site diagnosis of insects, showcasing the wide applicability of this method. [ABSTRACT FROM AUTHOR]

Aims: Vibrio harveyi is a serious pathogen for marine organisms particularly in hatcheries and grow-out ponds that attack their immune system. The rapid detection of V. harveyi is urgently needed to prevent bacterial spread. Here we described a rapid and specific visual detection method based on the Loop-Mediated Isothermal Amplification in combination with Lateral Flow Dipstick (LAMP-LFD). Methodology and results: A set of six novel primers were designed to target the toxR gene. These include the biotinlabelled inner primer that complements specifically to the target sequences. The resulting biotinylated LAMP amplicons were hybridised to the FAM-labelled probe resulting in lateral flow detection on the dipstick. The addition of loop primers improved the reaction time of LAMP by more than half and rapid detection was observed within 10-15 min. In comparison, the sensitivity of PCR-UV analysis was only at 104 copies while LAMP-LFD was able to detect lower amounts at 103 copies. The LFD provided higher specificity and selectivity since hybridization with specific probes to the LAMP amplicons was employed. In addition, detection of V. harveyi infected grouper was successful using the LAMPLFD method described here. Conclusion, significance and impact of study: LAMP-LFD is specific to V. harveyi. Our method provides a useful tool to rapidly detect and monitor the outbreaks of the pathogen. [ABSTRACT FROM AUTHOR]

Avian influenza viruses (AIV) pose a significant persistent threat to the public health and safety. It is estimated that there have been over 100 outbreaks caused by various H7 subtypes of avian influenza viruses (AIV-H7) worldwide, resulting in over 33 million deaths of poultry. In this study, we developed a recombinaseaided amplification combined with a lateral flow dipstick assay for the detection of hemagglutinin (HA) genes to provide technical support for rapid clinical detection of AIV-H7. The results showed that the assay can complete the reaction within 30 min at a temperature of 39°C. Specificity tests demonstrated that there was no cross-reactivity with other common poultry pathogens, including Newcastle disease virus (NDV) and infections bronchitis virus (IBV). The detection limit of this assay was 1 × 10¹ copies/µL, while RT-qPCR method was 1 × 10¹ copies/µL, and RT-PCR was 1 × 10² copies/µL. The κ value of the RT-RAA-LFD and RT-PCR assay in 132 avian clinical samples was 0.9169 (p < 0.001). These results indicated that the developed RT-RAA-LFD assay had good specificity, sensitivity, stability and repeatability and may be used for rapid detection of AIV-H7 in clinical diagnosis. [ABSTRACT FROM AUTHOR]

Identification of body fluids is critical for crime scene reconstruction, and a source of investigation source of investigative leads. In recent years, microbial DNA analysis using sequencing and quantitative real-time polymerase chain reaction have been used to identify body fluids. However, these techniques are time-consuming, expensive, and require complex workflows. In this study, a new method for simultaneous detection of Streptococcus salivarius and Lactobacillus crispatus using polymerase chain reaction (PCR) in combination with a lateral flow dipstick (LFD) was developed to identify saliva and vaginal fluid in forensic samples. LFD results can be observed with the naked eye within 3 min with a sensitivity of 0.001 ng/µL DNA. The PCR-LFD assay was successfully used to detect S. salivarius and L. crispatus in saliva and vaginal fluid respectively, and showed negative results in blood, semen, nasal fluid, and skin. Moreover, saliva and vaginal fluid were detectable even at an extremely high mixing ratio of sample DNA (1:999). Saliva and vaginal fluid were identified in various mock forensic samples. These results indicate that saliva and vaginal fluid can be effectively detected by identifying S. salivarius and L. crispatus, respectively. Furthermore, we have shown that DNA samples used to identify saliva and vaginal fluid can also provide a complete short tandem repeat (STR) profile when used as source material for forensic STR profiling. In summary, our results suggest that PCR-LFD is a promising assay for rapid, simple, reliable, and efficient identification of body fluids. [ABSTRACT FROM AUTHOR]

Echinococcosis poses a significant concern in the fields of public health and veterinary care as it can be transmitted between animals and humans. The primary endemic subtypes are cystic echinococcosis (CE) and alveolar echinococcosis (AE), which result from infestation by Echinococcus granulosus and Echinococcus multilocularis, respectively. A prominent epidemic of echinococcosis greatly affects the Tibet Autonomous Region (TAR) in China. A new technique called the loop-mediated isothermal amplification–lateral flow dipstick (LAMP-LFD) test is introduced in this research to differentiate between E. granulosus and E. multilocularis using their repetitive genetic sequences. The test is characterized by its portable nature, simple operation, quick result production, high sensitivity, and low susceptibility to aerosol contamination. The LAMP-LFD method demonstrated an exceptional minimal detection limit, reaching levels as low as approximately 1 fg/μL (femtogram per microliter) of genomic DNA. The assay’s specificity was assessed, and no cross-reactivity was seen. A total of 982 dog fecal samples were collected from 54 counties in the TAR region between July 2021 and June 2022. The established method underwent validation using a commercially available ELISA kit. The agreement rate between the LAMP-LFD and ELISA methods was 97.25%, with a sensitivity of 96.05% and a specificity of 97.35%. The assay described in this study improves specificity by using a double-labeled probe, and it reduces the risk of false-positive results caused by aerosol contamination through the use of a sealed device. This makes it a suitable choice for quickly and accurately identifying the two main types of Echinococcus in field settings.

Deformed wing virus (DWV) is one of the important pathogens of the honey bee (Apis mellifera), which consists of three master variants: types A, B, and C. Among them, DWV types A (DWV-A) and B (DWV-B) are the most prevalent variants in honey bee colonies and have been linked to colony decline. DWV-A and DWV-B have different virulence, but it is difficult to distinguish them via traditional methods. In this study, we established a visual detection assay for DWV-A and DWV-B using recombinase polymerase amplification (RPA) and a lateral flow dipstick (LFD) coupled with the clustered regularly interspaced short palindromic repeats (CRISPR)–CRISPR-associated protein (Cas) 12a fluorescence system (RPA–CRISPR–Cas12a–LFD). The limit of detection of this system was ~6.5 × 100 and 6.2 × 101 copies/μL for DWV-A and DWV-B, respectively. The assays were specific and non-cross-reactive against other bee viruses, and the results could be visualized within 1 h. The assays were validated by extracting cDNA from 36 clinical samples of bees that were suspected to be infected with DWV. The findings were consistent with those of traditional reverse transcription–quantitative polymerase chain reaction, and the RPA–CRISPR–Cas12a assay showed the specific, sensitive, simple, and appropriate detection of DWV-A and DWV-B. This method can facilitate the visual and qualitative detection of DWV-A and DWV-B as well as the monitoring of different subtypes, thereby providing potentially better control and preventing current and future DWV outbreaks. [ABSTRACT FROM AUTHOR]

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Apple stem grooving virus (ASGV) is one of the most widespread and asymptomatic main viruses, that restricts the production of apples worldwide. Establishment of rapid, simple, and effective early detection methods of apple virus is important. In this study, we established and optimized a one-step reverse transcription - recombinase polymerase amplification (RT-RPA) method, using the target-specific primers of ASGV coat protein gene sequence, and M-MLV reverse transcriptase. This method could be completed within 30 min at 40 °C, followed by a visual detection of the results within 5 min by using lateral flow dipstick (LFD). The specificity results showed that only samples infected with ASGV showed a test line, while no test line appeared in the ASGV-negative samples. In addition, when crude extract of leaves was used, the whole detection could be completed within 1 h, which was shortened by 4 to 6 times compared with the RT-PCR method. The detection made on more field samples showed that the RT-RPA-LFD method is of high stability and reliability for ASGV diagnosis, with a great potential in the rapid on-site detection of plant viruses.

Porcine deltacoronavirus (PDCoV) is an emerging enteropathogen causing severe diarrhoea, dehydration, and death in nursing piglets and enormous economic losses for the global swine industry. Furthermore, it can infect multiple animal species including humans. Therefore, a rapid, definitive diagnostic assay is required for the effective control of this zoonotic pathogen. To identify PDCoV, we developed a nucleic acid detection assay combining reverse transcription recombinase-aided amplification (RT-RAA) with a lateral flow dipstick (LFD) targeting the highly conserved genomic region in the ORF1b gene. The RT-RAA-LFD assay exhibited good PDCoV detection reproducibility and repeatability and could be completed within 11 min. Ten minutes at 40 °C was required for nucleic acid amplification and 1 min at room temperature was needed for the visual LFD readout. The assay specifically detected PDCoV and did not cross-react with any other major swine pathogens. The 95% limit of detection (LOD) was 3.97 median tissue culture infectious dose PDCoV RNA per reaction. This performance was comparable to that of a reference TaqMan-based real-time RT-PCR (trRT-PCR) assay for PDCoV. Of 149 swine small intestine, rectal swab, and serum samples, 71 and 75 tested positive for PDCoV according to RT-RAA-LFD and trRT-PCR, respectively. The diagnostic coincidence rate for both assays was 97.32% (145/149) and the kappa value was 0.946 (p

Rapid detection of bovine viral diarrhea virus (BVDV) is a key method to control bovine viral diarrhea (BVD). Recombinase polymerase amplification (RPA) is a new nucleic acid isothermal amplification technology. This study established a lateral flow dipstick RPA (LFD-RPA) detection method for BVDV detection based on the conserved DNA sequence of 5' non-coding region (5'-NCR) of the BVDV genome. The optimum reaction time and the optimum reaction temperature were 15 mins and 35°C, respectively, and the minimum detection amount of BVDV cDNA was 5.8×10-2 ng/µL. The results showed that the LFD-RPA method had superior sensitivity, specificity, and reproducibility. Furthermore, the method was more rapid and convenient, and was suitable for the detection of BVDV in the field. [ABSTRACT FROM AUTHOR]

The Clustered Regularly Interspaced Short Palindromic Repeats‐associated (CRISPR‐Cas) system has been used as a powerful diagnostic tool because of its trans‐cleavage ability to accurately recognize and cleave specific nucleic acid targets. However, its application in insect pest detection has rarely been reported. The aim of the current study was to develop a new molecular identification method for insect based on CRISPR‐Cas13a system. In this study, we have developed a highly specific and sensitive detection system that combines polymerase chain reaction, CRISPR‐Cas13a system and lateral flow dipstick (PCR‐Cas13a‐LFD) to rapidly detect the presence of Locusta migratoria manilensis (Orthoptera: Acrididae) DNA and discriminate it from other species, by using material from different stages of development. A pair of specific primers and crRNA were designed based on the Gene DEAD‐box DDX10 mRNA sequence. For visual readout, a FAM‐RNA‐biotin reporter was used for detection. The CRISPR‐Cas13a‐based detection method utilizes the visual identification of L. migratoria manilensis at different developmental stages or with the use of incomplete samples. The test results could be distinguished within 2 h. The sensitivity of the PCR‐Cas13a‐LFD detection system reached 0.1 ng/μL, a 10‐fold increase compared with that of the PCR with electrophoresis. The LFD coupled with CRISPR‐Cas13a (Cas13a‐LFD) is promising for the portable, onsite and fast identification of insect pests. This study provides a reference for the development of a new method for insect identification. [ABSTRACT FROM AUTHOR]

Vibrio parahaemolyticus has become an important public threat to human health. Rapid and robust pathogen diagnostics are necessary for monitoring its outbreak and spreading. Herein, we report an assay for the detection of V. parahaemolyticus based on recombinase aided amplification (RAA) combined with lateral flow dipstick (LFD), namely RAA-LFD. The RAA-LFD took 20 min at 36~38 ℃, and showed excellent specificity. It detected as low as 6.4 fg/µL of V. parahaemolyticus in genomic DNA, or 7.4 CFU/g spiked food samples with 4 h of enrichment. The limit of detection in shrimp (Litopenaeus Vannamei), fish (Carassius auratus), clam (Ruditapes philippinarum) evidenced that sensitivity was considerably affected by the food matrix. The presence of food matrix reduced the sensitivity of spiked food samples by 10 ~ 100 times. In the filed samples detection, RAA-LFD method showed good coincidence with GB4789.7-2013 method and PCR method at rates of 90.6% and 94.1%, respectively. RAA-LFD has high accuracy and sensitivity for the detection of V. parahaemolyticus, which can serve as a model tool to meet the growing need for point-of-care diagnosis of V. parahaemolyticus. [ABSTRACT FROM AUTHOR]