CADEM: Species-level detection of mycobacterial cfDNA via CRISPR for pulmonary disease diagnosis.

BACKGROUND

Pulmonary infections caused by Mycobacterium tuberculosis (MTB) and nontuberculous mycobacteria (NTM) present significant clinical challenges due to overlapping symptoms and different treatments. In particular, accurate identification of NTM species such as Mycobacterium avium complex (MAC) and Mycobacterium abscessus complex (MABC) is essential, as these species show drug susceptibility profiles that differ markedly from MTB. However, conventional culture-based diagnostics are time-consuming, and current molecular assays often lack resolution and rely heavily on sputum specimens. To address these limitations, liquid biopsy using bacterial-derived circulating cell-free DNA (cfDNA) offers a minimally invasive alternative, and CRISPR/Cas12a technology provides the sensitivity required to detect its low levels.

RESULTS

We developed CADEM (CRISPR-Assisted Detection via Enrichment of Mycobacterium-derived cfDNA using Microfluidic technology), a streamlined diagnostic system that integrates microfluidic cfDNA enrichment, targeted amplification, and CRISPR/Cas12a-based detection. The microfluidic platform enables high-yield recovery of cfDNA from large-volume clinical samples without the need for cell lysis. Optimized Cas12a-crRNA complexes enable highly sensitive and specific detection of MAC-, MABC-, and MTB -specific amplicons, achieving 10- to 100-fold greater sensitivity than end-point PCR and probe-based real-time PCR. In a validation set of 20 clinical specimens (7 positives and 13 healthy controls), CADEM identified all MAC, MABC, and MTB cases with full accuracy and no false positives. The CRISPR detection step produced a clear fluorescence readout within 20 min and, together with enrichment and amplification, delivered species-level results within a 2-h workflow.

SIGNIFICANCE: CADEM offers an accurate and streamlined molecular approach for distinguishing MAC, MABC, and MTB at the species-level to support appropriate diagnosis and treatment. By combining microfluidic cfDNA enrichment with CRISPR-based detection, CADEM enables efficient analysis from liquid biopsy samples for pulmonary disease diagnosis. The system is also compatible with isothermal amplification, supporting future adaptation for point-of-care testing in resource-limited settings.