Rapid detection of human mastadenovirus species B by recombinase polymerase amplification assay

Rapid and specific detection of Pentastiridius leporinus by recombinase polymerase amplification assay

Pentastiridius leporinus (Hemiptera: Cixiidae) is the main vector of an emerging and fast spreading sugar beet disease, the syndrome 'basses richesses' (SBR), in different European countries. The disease is caused by the γ-3-proteobacterium 'Candidatus Arsenophonus phytopathogenicus' and the phytoplasma 'Candidatus Phytoplasma solani' which are exclusively transmitted by planthoppers and can lead to a significant loss of sugar content and yield. Monitoring of this insect vector is important for disease management. However, the morphological identification is time consuming and challenging as two additional cixiid species Reptalus quinquecostatus and Hyalesthes obsoletus with a very close morphology have been reported in sugar beet fields. Further, identification of females and nymphs of P. leporinus at species level based on taxonomic key is not possible. In this study, an isothermal nucleic acid amplification based on recombinase polymerase amplification (RPA) was developed to specifically detect P. leporinus. In addition, real-time RPA was developed to detect both adults (male and female) and nymph stages using pure or crude nucleic acid extracts. The sensitivity of the real-time RPA for detection of P. leporinus was comparable to real-time PCR, but a shorter time (< 7 min) was required. This is a first report for real-time RPA application for P. leporinus detection using crude nucleic acid templates which can be applied for fast and specific detection of this vector in the field.

Rapid detection of human adenovirus subgroup B using recombinase polymerase amplification assay

Human adenovirus subgroup B (HAdV B) is one of the major pathogens of human respiratory virus infections, which has considerable transmission and morbidity in a variety of populations. Therefore, rapid and specific detection of HAdV B in clinical samples is essential for diagnosis. This study aimed to develop a product for rapid nucleic acid detection of HAdV B using recombinase polymerase amplification assay (RPA) and validate the performance of this method by using clinical samples. Results showed that this method achieved a lower limit of detection (LOD) of 10 copies/μL and had no cross-reactivity with other adenovirus subgroups or respiratory pathogens. In addition to high sensitivity, it can be completed within 30 min at 40 °C. There is no need to perform nucleic acid extraction on clinical samples. Taking qPCR as the gold standard, the RPA assay possessed a high concordance (Cohen's kappa, 0.896; 95% CI 0.808-0.984; P < 0.001), with a sensitivity of 87.80% and a specificity of 100.00%. The RPA assay developed in this study provided a simple and highly specific method, making it an important tool for rapid adenovirus nucleic acid detection and facilitating large-scale population screening in resource-limited settings.

Preliminary Evaluation of Rapid Visual Identification of Burkholderia pseudomallei Using a Newly Developed Lateral Flow Strip-Based Recombinase Polymerase Amplification (LF-RPA) System

Burkholderia pseudomallei is an important infectious disease pathogen that can cause melioidosis. Melioidosis is mainly prevalent in Thailand, northern Australia and southern China and has become a global public health problem. Early identification of B. pseudomallei is of great significance for the diagnosis and prognosis of melioidosis. In this study, a simple and visual device combined with lateral flow strip-based recombinase polymerase amplification (LF-RPA) was developed, and the utility of the LF-RPA assay for identifying B. pseudomallei was evaluated. In order to screen out the optimal primer probe, a total of 16 pairs of specific primers targeting the orf2 gene of B. pseudomallei type III secretion system (T3SS) cluster genes were designed for screening, and F1/R3 was selected as an optimal set of primers for the identification of B. pseudomallei, and parameters for LF-RPA were optimized. The LF-RPA can be amplified at 30-45°C and complete the entire reaction in 5-30 min. This reaction does not cross-amplify the DNA of other non-B. pseudomallei species. The limit of detection (LOD) of this assay for B. pseudomallei genomic DNA was as low as 30 femtograms (fg), which was comparable to the results of real-time PCR. Moreover, 21 clinical B. pseudomallei isolates identified by 16S rRNA gene sequencing were retrospectively confirmed by the newly developed LF-RPA system. Our results showed that the newly developed LF-RPA system has a simple and short time of operation and has good application prospect in the identification of B. pseudomallei.

Advanced Point-of-Care Testing Technologies for Human Acute Respiratory Virus Detection

The ever-growing global threats to human life caused by the human acute respiratory virus (RV) infections have cost billions of lives, created a significant economic burden, and shaped society for centuries. The timely response to emerging RVs could save human lives and reduce the medical care burden. The development of RV detection technologies is essential for potentially preventing RV pandemic and epidemics. However, commonly used detection technologies lack sensitivity, specificity, and speed, thus often failing to provide the rapid turnaround times. To address this problem, new technologies are devised to address the performance inadequacies of the traditional methods. These emerging technologies offer improvements in convenience, speed, flexibility, and portability of point-of-care test (POCT). Herein, recent developments in POCT are comprehensively reviewed for eight typical acute respiratory viruses. This review discusses the challenges and opportunities of various recognition and detection strategies and discusses these according to their detection principles, including nucleic acid amplification, optical POCT, electrochemistry, lateral flow assays, microfluidics, enzyme-linked immunosorbent assays, and microarrays. The importance of limits of detection, throughput, portability, and specificity when testing clinical samples in resource-limited settings is emphasized. Finally, the evaluation of commercial POCT kits for both essential RV diagnosis and clinical-oriented practices is included.

Development and evaluation of a loop-mediated isothermal amplification assay for clinical diagnosis of respiratory human adenoviruses emergent in China

Three human adenovirus (HAdV) genotypes, HAdV-7, HAdV-14, and HAdV-55, emerged as the most prevalent variants in China over the past decade and caused both sporadic, fatal cases and frequent, large outbreaks. Early diagnosis is essential to control infections and endemics. Here, we established a loop-mediated isothermal amplification (LAMP) assay coupled with an instrument-free nucleic acid extraction device recently developed by our group; the assay could detect all the 3 prevalent HAdV genotypes. Specificity analysis showed no cross-reactivity with other common respiratory pathogens and the analytical sensitivity was as low as 10 copies/μL. All detection steps could be completed within 1 hour. The assay's performance was evaluated using clinical samples and compared with the gold standard RT-PCR method, showing highly consistent results. The LAMP assay developed here could be readily used in basic laboratory facilities and with minimal DNA extraction equipment, and as a reliable screening test in a resource-limited setting.

Rapid Detection of Pathogens in Wound Exudate via Nucleic Acid Lateral Flow Immunoassay

The rapid detection of pathogens in infected wounds can significantly improve the clinical outcome. Wound exudate, which can be collected in a non-invasive way, offers an attractive sample material for the detection of pathogens at the point-of-care (POC). Here, we report the development of a nucleic acid lateral flow immunoassay for direct detection of isothermally amplified DNA combined with fast sample preparation. The streamlined protocol was evaluated using human wound exudate spiked with the opportunistic pathogen Pseudomonas aeruginosa that cause severe health issues upon wound colonization. A detection limit of 2.1 × 10⁵ CFU per mL of wound fluid was achieved, and no cross-reaction with other pathogens was observed. Furthermore, we integrated an internal amplification control that excludes false negative results and, in combination with the flow control, ensures the validity of the test result. The paper-based approach with only three simple hands-on steps has a turn-around time of less than 30 min and covers the complete analytical process chain from sample to answer. This newly developed workflow for wound fluid diagnostics has tremendous potential for reliable pathogen POC testing and subsequent target-oriented therapy.