The risk score of the CDI signature was calculated using the following formula: Risk Score = 0.003 × ATP6V0D1 + 0.101 × ATP6V1B1 − 0.052 × DRAM2 + 0.003 × GPSM1 + 0.059 × LRRK2 + 0.052 × MAPK3 + 0.053 × PINK1 − 0.157 × RRAGB + 0.046 × AKT2 + 0.433 × CIDEC − 0.221 × HTRA2 + 0.097 × PTGIS + 0.275 × STK24 − 0.110 × BAG4 + 0.023 × CASP4 + 0.041 × TNFRSF12A + 0.151 × TNFRSF8 + 0.040 × TRADD. Here, HTRA2 is linked to clostridium difficile infection.