Loop-mediated isothermal amplification for Candida species surveillance in under-resourced setting: a review of evidence

Diagnosing invasive fungal infections in the laboratory today: It's all good news?

Despite the advances in medical science, invasive fungal infections (IFI) remain a diagnostic challenge. The increasing prevalence of IFI, driven by immunosuppressive therapies, advances in intensive care and emerging pathogens, underscores the need for early and accurate diagnosis. This review evaluates current laboratory methods for the diagnosis of IFI, highlighting their strengths and limitations. Conventional techniques, including fungal culture, direct microscopy, and histopathology, remain the gold standard for the diagnosis of proven IFIs. These methods allow pathogen isolation, species identification and antifungal susceptibility testing. However, these techniques have limitations in terms of sensitivity and turnaround times. Although microscopy is a rapid technique, its sensitivity and species discrimination profile are limited. Modern serological assays, such as β-d-glucan and galactomannan detection, have improved the diagnostic accuracy of probable IFI cases. Integration of these assays with clinical and radiological findings, enables earlier intervention, although this is accompanied by an increased risk of false positives and necessitates careful clinical correlation. Molecular diagnostics, particularly polymerase chain reaction (PCR), allow rapid, species-specific identification directly from clinical samples. The advent of MALDI-TOF mass spectrometry has further improved diagnostic efficiency, particularly for yeast identification, although challenges remain for filamentous fungi. Innovative techniques, such as metagenomic sequencing, lateral-flow assays, and loop-mediated isothermal amplification, offer the potential for rapid and precise detection, even in resource-limited settings. The combination of conventional and innovative methods provides a comprehensive diagnostic framework. The continuous refinement of these tools, in conjunction with multidisciplinary collaboration, is imperative to improve the early diagnostic and targeted treatment of patients with IFI.

Assessment of LAMPAuris for Rapid Detection of Candida auris in Clinical Specimens

Candida auris is a pathogenic yeast frequently exhibiting multidrug resistance and thus warrants special attention. The prompt detection and proper identification of this organism are needed to prevent its spread in healthcare facilities. The authors of this paper had previously developed LAMPAuris, a loop-mediated isothermal amplification assay, for the specific detection of C. auris. LAMPAuris is evaluated in this report for its ability to identify C. auris from five clades and to detect it from clinical specimens. A total of 103 skin swab samples were tested in comparison with a culture-based method and C. auris-specific SYBR green qPCR. The results show that the LAMPAuris assay had specificities ranging from 97 to 100% and sensitivities ranging from 66 to 86%. The lower sensitivity could be attributed to DNA degradation caused by the prolonged storage of the samples. In conclusion, LAMPAuris proved to be a rapid and reliable method for identifying C. auris and for detecting it in clinical specimens. Fresh specimens should ensure better yield and higher sensitivities.

The clinical value of rapidly detecting urinary exosomal lncRNA RMRP in bladder cancer with an RT-RAA-CRISPR/Cas12a method

BACKGROUND AND AIMS

Bladder cancer (BCa) is a highly aggressive malignancy of the urinary system. Timely detection is imperative for enhancing BCa patient prognosis.

MATERIALS AND METHODS

This study introduces a novel approach for detecting long non-coding RNA (lncRNA) Mitochondrial RNA Processing Endoribonuclease (RMRP) in urine exosomes from BCa patients using the reverse transcription recombinase-aided amplification (RT-RAA) and clustered regularly interspaced short palindromic repeats and associated Cas12a proteins (CRISPR/Cas12a) technique. Various statistical methods were used to evaluate its diagnostic value for BCa.

RESULTS

The specificity of urine exosomal RMRP detection for BCa diagnosis was enhanced by using RT-RAA combined with CRISPR/Cas12a. The testing process duration was reduced to 30 min, which supports rapid detection. Moreover, this approach allows the identification of target signals in real-time using blue light, facilitating immediate detection. In clinical sample analysis, this methodology exhibited a high level of diagnostic efficacy. This was evidenced by larger area under the curve values with receiver operating characteristic curve analysis compared with using traditional RT-qPCR methods, indicating superior diagnostic accuracy and sensitivity. Furthermore, the combined analysis of RMRP expression in urine exosomes detected by RT-RAA-CRISPR/Cas12a and NMP-22 expression may further enhance diagnostic accuracy.

CONCLUSIONS

The RT-RAA-CRISPR/Cas12a technology is a swift, sensitive, and uncomplicated method for nucleic acid detection. Because of its convenient and non-invasive sampling approach, user-friendly operation, and reproducibility, this technology is very promising for automated detection and holds favorable application possibilities within clinical environments.

Reverse transcription loop-mediated isothermal amplification (RT-LAMP) primer design based on Indonesia SARS-CoV-2 RNA sequence

BACKGROUND

The COVID-19 pandemic has highlighted the importance of tracking cases by using various methods such as the Reverse transcription loop-mediated isothermal amplification (RT-LAMP) which is a fast, simple, inexpensive, and accurate mass tracker. However, there have been no reports about the development of RT-LAMP primer designs that use genome sequences of viruses from Indonesia. Therefore, this study aimed to design an RT-LAMP primer using SARS-CoV-2 genome sequences from Indonesia and several other countries representing five continents in the world, as well as genomes from five Variants of Concern (VOC).

RESULT

The results showed that the consensus sequence of 70 SARS-CoV-2 virus sequences was obtained with a length of 29,982 bases. The phylogenetic test confirmed that the consensus sequence had a close kinship with the SARS-CoV-2 Wuhan Isolate. Furthermore, the SimPlot analysis showed that there was a high genetic diversity of sequences from the Coronaviridae tribal virus at base sequences of 1,500-5,000, 6,500-7,500, and 23,300-25,500. A total of 139 sets of primers were obtained from the primer design with 4 sets namely T1_6, T1_9, T4_7, and T4_52 having the best characteristics. Based on the secondary structure analysis test on 4 sets of primers, T1_6 and T1_9 were predicted not to form secondary structures at RT-LAMP operational temperatures. The primer set T1_9 showed better specificity in BLAST NCBI and eLAMP BLAST tests.

CONCLUSION

This study obtained a primer set of T1_9 with base sequence F3: CACTGAGACTCATTGATGCTATG, B3: CCAACCGTCTCTAAGAAACTCT, F2: GTTCACATCTGATTTGGCTACT, F1c: GAAGTCAACTGAACAACACCACCT, B2: CCTTCCTTAAACTTCTCTTCAAGC, B1c: GTGGCTAACTAACATCTTTGGCACT, LB: TGAAAACAAACCCGCCGTCCTTG, which meets the ideal parameters and has the best specificity. Therefore, it is recommended for use in further tests to recognize SARS-CoV-2 from Indonesia, other five continents, as well as five VOCs, including the new Omicron sub-variant.

An Integrated and Multi-Target Nucleic Acid Isothermal Analysis System for Rapid Diagnosis of Vulvovaginal Candidiasis

Rapid identification of Candida species is significant for the diagnosis of vulvovaginal candidiasis (VVC). An integrated and multi-target system for the rapid, high-specificity, and high-sensitivity detection of four Candida species was developed. The system consists of a rapid sample processing cassette and a rapid nucleic acid analysis device. The cassette could process the Candida species to release nucleic acids in 15 min. The released nucleic acids were analyzed by the device as fast as within 30 min, using the loop-mediated isothermal amplification method. The four Candida species could be simultaneously identified, with each reaction using only 1.41 µL of reaction mixture, which was low cost. The RPT (rapid sample processing and testing) system could detect the four Candida species with high sensitivity (<2 CFU/reaction) and high specificity. The system also processed and analyzed 32 clinical samples, giving the results with high clinical sensitivity and specificity. Hence, the system was a significant and effective platform for the diagnosis of VVC. Furthermore, the period of validity of the reagents and chips used in the system was >90 days, and the system could also be used for the detection of bacteria.

Diagnostic Efficacy of LAMP Assay for Human Fungal Pathogens: a Systematic Review and Meta-analysis

Purpose

Human fungal infections particularly caused by Candida and Aspergillus have emerged as major public health burden. Long turnaround time and poor sensitivity of the conventional diagnostics are the major impediments for faster diagnosis of human fungal pathogens.

Recent Findings

To overcome these issues, molecular-based diagnostics have been developed. They offer enhanced sensitivity but require sophisticated infrastructure, skilled manpower, and remained expensive. In that context, loop-mediated isothermal amplification (LAMP) assay represents a promising alternative that facilitates visual read outs. However, to eradicate fungal infections, all forms of fungi must be accurately detected. Thus, a need for alternative testing methodologies is imperative that should be rapid, accurate and facilitate widespread adoption. Therefore, the aim of the present study is to conduct a meta-analysis to assess the diagnostic efficiency of LAMP in the detection of a panel of human fungal pathogens following PRISMA guidelines using scientific databases viz. PubMed, Google Scholar, Science Direct, Scopus, BioRxiv, and MedRxiv.

Summary

From various studies reported on the diagnosis of fungi, only 9 articles were identified as eligible to meet the criteria of LAMP based diagnosis. Through this meta-analysis, it was found that most of the studies were conducted in China and Japan with sputum and blood as the most common specimens to be used for LAMP assay. The collected data underlined that ITS gene and fluorescence-based detections ranked as the most used target and method. The pooled sensitivity values of meta-analysis ranged between 0.71 and 1.0 and forest plot and SROC (summary receiver operating characteristic) curve revealed a pooled specificity values between 0.13 and 1.0 with the confidence interval of 95%, respectively. The accuracy and precision rates of eligible studies mostly varied between 70 to 100% and 68 to 100%, respectively. A quality assessment based on QUADAS-2 (Quality Assessment of Diagnostic Accuracy Studies) of bias and applicability was conducted which depicted low risk of bias and applicability concerns. Together, LAMP technology could be considered as a feasible alternative to current diagnostics considering high fungal burden for rapid testing in low resource regions.

Sensitive and rapid RT-RPA-Cas12a-mediated detection method capable of human rhinovirus A and/or C species by targeting VP4

Human rhinovirus (HRV), the main etiologic agent of the common cold, is responsible for significant morbidity, medical costs, and the loss of productivity in the workplace and school. To prevent the spread of HRV, accurate, low-cost and rapid diagnostics of HRV is crucial for identifying those at-risk for the illness associated with HRV, with the most frequently detected species, including HRV species A (HRV-A) and C (HRV-C). Here, a novel HRV-A and/or HRV-C molecular diagnostic assay that integrates reverse-transcription recombinase polymerase amplification assay (RT-RPA) amplification with CRISPR/Cas12a detection, with the result readout using a fluorescence detector or lateral flow strip (LFS). The established assay could be completed within 50 min without complex instruments and skilled technicians. The limit of detection of the RT-RPA-Cas12a-mediated real-time fluorescence or LFS assay could reach 0.1 copy/μl, and 0.5 copy/μl for the end-point fluorescence assay with a UV light illuminator readout, respectively. Meanwhile, the assay demonstrates excellent specificity without cross-reactivity to non-target viruses. Furthermore, they were appraised using 80 clinical samples, and RT-RPA-Cas12a-mediated fluorescence or LFS assay displayed high-accuracy with positive and negative predictive agreement of 96.7%, 95% and 100%, respectively. Taken together, the RT-RPA-Cas12a-mediated assay is a rapid, sensitive, and specific detection tool for routine and on-site detection method for HRV-A and/or HRV-C infections, and shows great promise for use in resource-poor or constrained settings.