A low-cost and open-source protocol to produce key enzymes for molecular detection assays

Versatile and Portable Cas12a-mediated Detection of Antibiotic Resistance Markers

Antimicrobial resistance (AMR) is a global public health problem particularly accentuated in low- and middle-income countries, largely due to a lack of access to sanitation and hygiene, lack of awareness and knowledge, and the inadequacy of molecular laboratories for timely and accurate surveillance programs. This study introduces a versatile molecular detection toolbox (C12a) for antibiotic resistance gene markers using CRISPR/Cas12a coupled to PCR. Our toolbox can detect less than 3×10-7 ng of DNA (100 attoMolar) or 102 CFU/mL. High concordance was observed when comparing the C12a toolbox with sequenced genomes and antibiotic susceptibility tests for the blaCTX-M-15 and floR antibiotic resistance genes (ARGs), which confer resistance to cefotaxime and other β-lactams, and amphenicols, respectively. C12aINT, designed to detect the Integrase 1 gene, confirmed a high prevalence of the integrase/integron system in E. coli containing multiple ARGs. The C12a toolbox was tested across a wide range of laboratory infrastructure including a portable setup. When combined with lateral flow assays (LFA), C12a exhibited competitive performance, making it a promising solution for on-site ARG detection. Altogether, this work presents a collection of molecular tools (primers, crRNAs, probes) and validated assays for rapid, versatile, and portable detection of antibiotic resistance markers, highlighting the C12a toolbox potential for applications in surveillance and ARG identification in clinical and environmental settings.

Novel CRISPR-based detection of Leishmania species

Tegumentary leishmaniasis, a disease caused by protozoan parasites of the genus Leishmania, is a major public health problem in many regions of Latin America. Its diagnosis is difficult given other conditions resembling leishmaniasis lesions and co-occurring in the same endemic areas. A combination of parasitological and molecular methods leads to accurate diagnosis, with the latter being traditionally performed in centralized reference and research laboratories as they require specialized infrastructure and operators. Clustered regularly interspaced short palindromic repeats/CRISPR-associated protein (CRISPR/Cas) systems have recently driven innovative tools for nucleic acid detection that combine high specificity, sensitivity and speed and are readily adaptable for point-of-care testing. Here, we harnessed the CRISPR-Cas12a system for molecular detection of Leishmania spp., emphasizing medically relevant parasite species circulating in Peru and other endemic areas in Latin America, with Leishmania (Viannia) braziliensis being the main etiologic agent of cutaneous and mucosal leishmaniasis. We developed two assays targeting multi-copy targets commonly used in the molecular diagnosis of leishmaniasis: the 18S ribosomal RNA gene (18S rDNA), highly conserved across Leishmania species, and a region of kinetoplast DNA (kDNA) minicircles conserved in the L. (Viannia) subgenus. Our CRISPR-based assays were capable of detecting down to 5 × 10-2 (kDNA) or 5 × 100 (18S rDNA) parasite genome equivalents/reaction with PCR preamplification. The 18S PCR/CRISPR assay achieved pan-Leishmania detection, whereas the kDNA PCR/CRISPR assay was specific for L. (Viannia) detection. No cross-reaction was observed with Trypanosoma cruzi strain Y or human DNA. We evaluated the performance of the assays using 49 clinical samples compared to a kDNA real-time PCR assay as the reference test. The kDNA PCR/CRISPR assay performed equally well as the reference test, with positive and negative percent agreement of 100%. The 18S PCR/CRISPR assay had high positive and negative percent agreement of 82.1% and 100%, respectively. The findings support the potential applicability of the newly developed CRISPR-based molecular tools for first-line diagnosis of Leishmania infections at the genus and L. (Viannia) subgenus levels.

Open access methods and protocols promote open science in a pandemic

This Backstory discusses the development of a SARS-CoV-2 detection method using widely available laboratory equipment. The approach, reported in Cell Reports Methods and STAR Protocols, is intended as a diagnostic tool for COVID-19 that is accessible for resource-limited areas. We describe how the published method and protocols encourage adoption of the detection strategy in different areas and a variety of biological contexts.

For complete details on the UnCovid method and protocols, please refer to (Alcántara et al., 2021a; Alcántara et al., 2021b; Mendoza-Rojas, et al., 2021).

UnCovid: A versatile, low-cost, and open-source protocol for SARS-CoV-2 RNA detection

Here, we describe a detailed step-by-step protocol to detect SARS-CoV-2 RNA using RT-PCR-mediated amplification and CRISPR/Cas-based visualization. The optimized assay uses basic molecular biology equipment such as conventional thermocyclers and transilluminators for qualitative detection. Alternatively, a fluorescence plate reader can be used for quantitative measurements. The protocol detects two regions of the SARS-CoV-2 genome in addition to the human RNaseP sample control. Aiming to reach remote regions, this work was developed to use the portable molecular workstation from BentoLab. For complete details on the use and execution of this protocol, please refer to Alcántara et al., 2021.