Abstract
Lower respiratory tract infections (LRTIs) are among the leading causes of clinical deterioration and death in critically ill patients. In the intensive care unit (ICU), timely identification of the causative pathogen is essential for appropriate antimicrobial therapy; however, conventional culture methods take 3 to 5 days and have suboptimal positivity rates, particularly for fungi. Molecular approaches such as PCR shorten turnaround time but still depend on manual nucleic acid extraction and thermocycling, limiting their suitability for bedside use. This protocol describes a point-of-care workflow built around a fully integrated, disc-shaped microfluidic chip (CD chip) that couples magnetic bead-based nucleic acid purification with loop-mediated isothermal amplification (LAMP). After a simplified manual liquefaction and lysis step, the processed specimen is loaded onto the chip together with two prepackaged reagent vials. The instrument then autonomously performs extraction, amplification at 65 °C, and real-time fluorescence readout, returning qualitative results for 15 targets, namely 11 bacteria, 3 fungi, and 1 atypical pathogen, within 45 min of instrument run time (approximately 1 h for the complete sample-to-answer workflow, including the manual preprocessing step). We present detection data from 10 ICU specimens, including sputum, bronchial aspirates, and bronchoalveolar lavage fluid, encompassing both single-pathogen and polymicrobial co-infections involving up to 7 organisms on a single chip. The closed cartridge design minimizes the risk of aerosol contamination, and the single loading step requires no specialized training, positioning this system as a practical bedside diagnostic tool for ICU teams.