Direct and Rapid Detection and Quantification of Oenococcus oeni Cells in Wine by Cells-LAMP and Cells-qLAMP

A quantitative RT-qLAMP for the detection of SARS-CoV-2 and human gene in clinical application

Reverse transcription (RT) - loop-mediated isothermal amplification (LAMP) assay is a rapid and one-step method to detect SARS-CoV-2 in the pandemic. Quantitative estimation of the viral load of SARS-CoV-2 in patient samples could help physicians make decisions on clinical treatment and patient management. Here, we propose to use a quantitative LAMP (qLAMP) method to evaluate the viral load of SARS-CoV-2 in samples. We used threshold time (TT) values of qLAMP, the isothermal incubation time required for the fluorescent or colorimetric signal to reach the threshold, to indicate the viral load of clinical samples. Similar to the cycle threshold (Ct ) values in conventional qPCR, TT values of qLAMP show a linear relationship to the copy numbers of SARS-CoV-2. The higher the viral loadings, the lower qLAMP TT values are. The RT-qLAMP assay was demonstrated to quantify the viral loads of synthesized full-length RNA, inactivated viral particles (BBIBP-CorV), and clinical samples within 15 min by fluorescent reading and 25 min by colorimetric reading. The RT-qLAMP has been applied to detect Alpha, Beta, Kappa, Delta, and Omicron variants of SARS-CoV-2, as well as the human beta-actin gene, and their TT values showed the linear patterns. The RT-qLAMP assays were evaluated by 64 clinical samples (25 positives and 39 negatives) for the assessment of viral loads, and it was also used to quantify the human beta-actin gene, which was used as a control and an indicator of sampling quality in clinical swab samples. The result of RT-qLAMP was in good agreement with the result of RT-qPCR. The RT-qLAMP assay detected all clinical samples, including those with Ct  = 35, within 10 min using fluorescent reading.

Detection of Streptococcus pneumoniae in Urine by Loop-Mediated Isothermal Amplification

Objective To assess the loop-mediated isothermal amplification (LAMP) to detect cell-free DNA from Streptococcus pneumoniae in urine samples from children with pneumococcal pneumonia.

Methods LAMP reactions using four primers (backward inner primer, forward inner primer, B3, and F3) targeting conserved regions of the S. pneumoniae ply gene and DNA from the recombinant plasmid pTrc99A-ply were optimized for temperature (65°C) and MgSO4 concentration (8 mM) conditions. Urine samples from 71 patients with symptoms of pneumonia and from 17 healthy children were tested side by side using the isothermal methodology LAMP and the commercial urinary antigen test, BinaxNOW S. pneumoniae assay. Percentages of sensitivity, specificity, positive predictive value (PPV), negative predictive value, and positive (LR) were calculated to compare both tests.

Results The specificity of the LAMP reaction was confirmed against several species of bacteria and yeast that can cause pneumonia or urine infections. The suitability of the LAMP assay was evaluated in urine samples from 71 patients and 17 healthy children. All patients (100%) with confirmed pneumococcal pneumonia were positive for the LAMP assay. Among patients with possible/probable pneumonia, 74.1% were identified as positive using the LAMP test. Notably, a higher specificity (95.4%), PPV (94.1%) and positive LR (21.7) were found compared with the urinary antigen test.

Conclusion The presence of S. pneumoniae cell-free DNA in urine samples of pediatric patients can be used as a specific diagnostic biomarker for community-acquired pneumonia by using the LAMP methodology.

Development and application of a real-time loop-mediated isothermal amplification method for quantification of Acetobacter aceti in red wine

This study reports the development and optimization of a real-time loop-mediated isothermal amplification (qLAMP) method for rapid detection of Acetobacter aceti strain in red wine samples. Our results showed that the primers and probes designed for 16S rRNA were effective for A. aceti detection. The quantification limit of real-time polymerase chain reaction (qPCR) and qLAMP in pure culture was 2.05 × 101 colony forming units (CFU) mL-1. qLAMP had a sensitivity of 6.88 × 101 CFU mL-1 in artificially contaminated Changyu dry red wine (CDRW) and Changyu red wine (CRW), and 6.88 × 102 CFU mL-1 in artificially contaminated Greatwall dry red wine (GDRW), which was 10 times higher than that of qPCR. In conclusion, this newly developed qLAMP is a reliable, rapid and accurate method for the detection and quantification of A. aceti species in red wine samples. Furthermore, our work provides a standard reference method for the quantitative detection of A. aceti and other acetic acid bacteria during the fermentation and storage of red wine samples.