Suction Drain Tip Cultures in Predicting a Surgical Site Infection

STUDY DESIGN: Retrospective study. PURPOSE: This study aimed to evaluate the prognostic value of drain tip culture after spinal surgery with a large number of participants. OVERVIEW OF LITERATURE: The routine culture of suction drain tips that are placed in the surgical site of spinal surgeries has been performed in many institutions to detect surgical site infection (SSI). However, few reports have evaluated drain tip culture as a prognostic for SSI after spinal surgery. MATERIALS AND METHODS: This study retrospectively included 1,415 consecutive patients who underwent spinal surgery between January 2016 and December 2021. Patients diagnosed with infectious diseases were excluded. Prophylactic antibiotics were administered intraoperatively and 24 hours postoperatively. Drains were removed when the volume of postoperative fluid drainage was <50 mL and <100 mL in patients who underwent cervical and thoracic surgery and lumbar surgery in the preceding 24 hours, respectively, and cultures were made. We evaluated the correlation between the results of positive drain tip culture and SSI. RESULTS: Positive drain tip cultures were found in 51 cases (3.6%). SSI was identified in 34 cases (2.4%). The most frequently isolated microorganism was methicillin-resistant Staphylococcus epidermidis (61.8%). The sensitivity, specificity, and positive, and negative predictive values of drain tip culture were 50.0%, 97.4%, 32.1%, and 98.8%, respectively. The same bacteria were isolated from the surgical lesion in 16 of 17 SSI cases with a positive drain tip culture, thereby giving a bacteria matching rate between tissue culture and drain tip culture of 94.1%. The number of surgery levels, drain remaining period, and drain tip culture positivity were significantly increased in the SSI group. CONCLUSIONS: Drain tip cultures might be useful for predicting SSI. Drain tip culture had a high positivity rate in the SSI group, and the coincidence rate for the causative pathogen was high.