A 75-year-old woman presented with a 2-year history of right hip pain with restriction of movement. She had undergone right hip arthroplasty because of a traumatic fracture 16years previously;5years ago, she underwent a revision for joint pain and limit movement. She had no comorbidities. Her hip pain had recurred 2years ago, and she was treated with second-generation cephalosporin for her symptoms (night pain, elevated temperature, swollen area of the hip), and her erythrocyte sedimentation rate (ESR) was 60mm/h (normal range 0~10mm/h), and her C-reactive protein (CRP) concentration was 304mg/L (normal range 0~10mg/L). The lab test result came to normal, but the pain still existed after the antibiotic treatment. Her pain and disability had increased during the most recent 2months. The patient arrived at our hospital in a wheelchair. Physical examination showed that her right lower extremity was shortened and that her hip exhibited flexion contracture; the skin around the hip joint was red, swollen without sinus. Her preoperative ESR was 43mm/h, and her CRP was 20.4mg/L. Before the first stage, the X-ray film showed a massive bone defect of the proximal femur, making the leg shortened. Aspiration of the patients hip joint produced almost 30mL of synovial fluid. The synovial fluid examination revealed a white cell count (WBC) of 7548/mm3 with a polymorphonuclear neutrophil (PMN) percentage of 77%. We inoculated samples of the synovial fluid into four blood culture vials (two aerobic and two anaerobic vials) and cultured them using an instrumented blood culture system (BACTECTM FX 100, Becton, Dickinson and Company, New Jersey, US). The two anaerobic culture vials exhibited growth at 44 and 62h after inoculation, respectively; we then performed a Gram stain of the samples and found Gram-positive bacilli under microscopy. Gray-white wet colonies of medium size, round shape, and irregular edges were observed in the anaerobic medium after 24h of incubation. The organism was identified as C. difficile by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS, Bruker Corporation, Nehren, Germany). Identification was confirmed by 16S rRNA sequencing. Polymerase chain reaction tested (Tsingke company, Beijing, China) positively for the tcdA and tcdB genes of C. difficile. Antimicrobial testing showed that the bacterium was sensitive to metronidazole and vancomycin (Etest, BIOMERIEUX, Paris, France). We performed a two-stage revision for treatment of this patient. In the first stage, we removed the prosthesis and performed thorough debridement; this was followed by the placement of a cement spacer mixed with vancomycin. We mixed 4g vancomycin in 36g cement (PALACOSR, Heraeus Medical GmbH, Wehrheim, Germany). Intraoperative cultures of the synovial fluid and tissue repeatedly grew C. difficile. The antimicrobial susceptibility results were unchanged from the previous cultures. According to the results of antimicrobial testing, metronidazole was selected for treatment. The patient was treated with intravenous metronidazole for 2weeks postoperatively and oral metronidazole (400mg three times a day) for another 4weeks. She then underwent the second stage of hip reconstruction after confirming that her laboratory parameters were normal (CRP: 2.65mg/L; ESR: 26mm/h). We used a tumor prosthesis to reconstruct her femur bone defect. And we used augment to econstruct the acetabular. We obtained intraoperative samples again to ensure that the infection was under control. We checked an intraoperative cell count (WBC: 247/mm3; PMN percentage: 7%). Cultures of all samples showed no growth, and the patient underwent another round of antibiotic treatment (2weeks of intravenous metronidazole and another 4weeks of oral metronidazole, as before). She returned for regular follow-ups. At her latest follow-up, 1year after the diagnosis of PJI due to C. difficile, her right hip was pain-free, and the incision had healed without clinical signs of infection.