APEH and clostridium difficile infection: For example, APH (2′′) was found in most samples (100, 93.75, and 100% in healthy, COPD, and CDI, respectively; Supplementary Table S5), but showed significantly different abundances between the groups (p < 0.05 for all pairs; 23.6, 45.7, and 334.6 RPKM for average abundance in the healthy, COPD, and CDI groups, respectively).