Rapid, Simple, and Highly Specific Detection of Streptococcus pneumoniae With Visualized Recombinase Polymerase Amplification

Low-Frequency Optical Signal Enhancement Device Combines CRISPR-Based Assay for Portable S. Pneumoniae Detection

Early detection and treatment of Streptococcus pneumoniae (SPN) is crucial for patients. However, since nucleic acid testing relies on large-scale equipment and specialized operators, challenges remain for accurate, fast, and low-cost SPN detection. Here, we present a point-of-care testing (POCT) device for rapid and accurate detection of SPN based on low-frequency optical signal enhancement and cluster of regularly interspaced short palindromic repeats (CRISPR). The spotlight tube enables the enhancement of the fluorescence signal, while the combination of an artificial intelligence-assisted autoexposure algorithm and a homomorphic filtering image processing method improves the signal-to-noise ratio of the fluorescence image, thus realizing highly sensitive detection. Nucleic acid identification is performed using CRISPR-based crRNAs, and fluorescent probes were constructed against the IytA gene of SPN. And they showed high specificity and sensitivity for the IytA gene. This device demonstrated excellent sensitivity in detecting the SPN using the developed CRISPR-based nucleic acid detection strategy. The detection threshold of SPN reached 0.1 fM, and the single detection time of the device was only 40 min. Specificity was validated using clinical samples, and the test showed 100% agreement with quantitative polymerase chain reaction results from clinical samples. This method provides a highly sensitive optical and signal processing device, which, in combination with a novel DNA probe for SPN, provides a novel indicator option for POCT of SPN.

Rapid detection of HPV16 utilizing recombinase polymerase amplification with the employment of an extremely low concentration of the probe

Human papillomavirus 16 (HPV16) infection is the leading cause of cervical cancer. The current mainstream method for detecting HPV16 is quantitative real-time PCR (qPCR). However, due to its time-consuming nature and reliance on expensive qPCR instruments, there is growing interest in more convenient, rapid and private approaches such as recombinase polymerase amplification (RPA). In this study, we innovated an effective method for HPV16 detection by integrating a RPA system with lateral flow strip (LFS) detection. Primers with optimal efficiency and specificity were designed, and false positive signals caused by dimers were eliminated by reducing the probe concentration. The RPA-LFS method demonstrates high sensitivity and specificity, capable of detecting 230 copies per reaction of HPV16 within 25 min without cross-reactivity to other subtypes. It exhibits good tolerance, remaining unaffected by 1.0% miconazole, 0.5% tioconazole and 1.0% hemoglobin. The results of clinical samples detected by this method were consistent with those of qPCR. The method provides a practical reference for HPV16 diagnosis and can be valuable in home and resource-limited settings, contributing to the reduction of cervical cancer incidence.

Efficient detection of Streptococcus pyogenes based on recombinase polymerase amplification and lateral flow strip

PURPOSE

This article aims to establish a rapid visual method for the detection of Streptococcus pyogenes (GAS) based on recombinase polymerase amplification (RPA) and lateral flow strip (LFS).

METHODS

Utilizing speB of GAS as a template, RPA primers were designed, and basic RPA reactions were performed. To reduce the formation of primer dimers, base mismatch was introduced into primers. The probe was designed according to the forward primer, and the RPA-LFS system was established. According to the color results of the reaction system, the optimum reaction temperature and time were determined. Thirteen common clinical standard strains and 14 clinical samples of GAS were used to detect the selectivity of this method. The detection limit of this method was detected by using tenfold gradient dilution of GAS genome as template. One hundred fifty-six clinical samples were collected and compared with qPCR method and culture method. Kappa index and clinical application evaluation of the RPA-LFS were carried out.

RESULTS

The enhanced RPA-LFS method demonstrates the ability to complete the amplification process within 6 min at 33 °C. This method exhibits a high analytic sensitivity, with the lowest detection limit of 0.908 ng, and does not exhibit cross-reaction with other pathogenic bacteria.

CONCLUSIONS

The utilization of RPA and LFS allows for efficient and rapid testing of GAS, thereby serving as a valuable method for point-of-care testing.

Fluorescent and electrochemical detection of nuclease activity associated with Streptococcus pneumoniae using specific oligonucleotide probes

Streptococcus pneumoniae (S. pneumoniae) represents a significant pathogenic threat, often responsible for community-acquired pneumonia with potentially life-threatening consequences if left untreated. This underscores the pressing clinical need for rapid and accurate detection of this harmful bacteria. In this study, we report the screening and discovery of a novel biomarker for S. pneumoniae detection. We used S. pneumoniae nucleases as biomarker and we have identified a specific oligonucleotide that works as substrate. This biomarker relies on a specific nuclease activity found on the bacterial membrane, forming the basis for the development of both fluorescence and electrochemical biosensors. We observed an exceptionally high sensitivity in the performance of the electrochemical biosensor, detecting as low as 102 CFU mL-1, whereas the fluorescence sensor demonstrated comparatively lower efficiency, with a detection limit of 106 CFU mL-1. Moreover, the specificity studies have demonstrated the biosensors' remarkable capacity to identify S. pneumoniae from other pathogenic bacteria. Significantly, both biosensors have demonstrated the ability to identify S. pneumoniae cultured from clinical samples, providing compelling evidence of the potential clinical utility of this innovative detection system.

Development and application of a universal extraction-free reagent based on an algal glycolipid

In this study, we independently developed a universal nasopharyngeal swab extraction-free reagent based on a trehalose lipid for the rapid detection of pathogen nucleic acids in respiratory infectious diseases. By comparing the isothermal amplification results of a 2019-nCoV pseudovirus solution treated with different components of the extraction-free reagent, we determined the optimal composition of the extraction-free reagent to be a mixed solution of 10 mmol L-1 tris-HCl containing 0.05 mmol L-1 EDTA (TE solution), 5% glycine betaine, 0.5% Triton X-100, and 1.5% trehalose lipid. The results showed that the extraction-free reagent could cleave DNA viruses, RNA viruses, and bacteria to release nucleic acids and did not affect the subsequent nucleic acid amplification. Its efficiency was consistent with that of magnetic bead extraction. Real-time fluorescence quantitative PCR was used to analyze the stability and repeatability of the detection results of the samples treated with the extraction-free reagent and the sensitivity of the extraction-free reagent. The results showed that the extraction-free kit could stably store the pathogen nucleic acid for at least 24 hours, the detection repeatability was satisfactory, and there was no incompatibility with the detection limits of various manufacturers' nucleic acid detection reagents. In conclusion, the established nucleic acid extraction-free method can effectively lyse respiratory infectious disease pathogens to release nucleic acids (DNA and RNA) at room temperature and can directly amplify nucleic acids without extraction steps. This method takes a short time and has high efficiency. The released nucleic acid met the requirements of molecular biological detection methods such as real-time fluorescence quantitative PCR (qPCR), reverse transcription-polymerase chain reaction (RT-PCR), and isothermal nucleic acid amplification (INAA).