Lower respiratory tract infections (LRITs), including community-acquired pneumonia (CAP), are the fifth leading cause of death worldwide over the last ten years, posing a serious threat to global healthcare. Conventional laboratory assays for detecting pathogens are hindered by complicated procedures, a long turnaround time and a lack of multiplex detection capabilities. In this study, a flap-endonuclease 1 (FEN1)-assisted loop-mediated isothermal amplification (LAMP) method was designed, and an assay based on this method was developed to identify three leading pathogens for CAP, namely,