Drain Tip Culture is Not Prognostic for Surgical Site Infection in Spinal Surgery Under Prophylactic Use of Antibiotics.

STUDY DESIGN A retrospective observational study. OBJECTIVE We evaluated the prognostic value of drain tip culture performed for surgical site infection (SSI) after spinal surgery with a large number of subjects, and investigated whether the type of surgery or timing of drain removal correlated with positive drain culture and SSI rates. SUMMARY OF BACKGROUND DATA In many institutions, routine culture of suction drain tips that are placed in the surgical site of spinal surgeries has been performed to detect contamination after removal. However, few reports have evaluated whether drain tip culture is prognostic for SSI after spinal surgery. METHODS A total of 1240 suction drain tips that had been used in spinal surgeries were cultured after removal. Prophylactic antibiotics were administered during and after the surgery for 48 hours. We evaluated the correlation between the results of positive drain tip culture, SSI, and drain removal timing. RESULTS Positive drain tip cultures were found in 55 cases (4.4%). True SSI was identified in 18 cases (1.5%). The most frequently isolated microorganism in the both cases was Staphylococcus. The sensitivity of drain tip culture for SSI after spinal surgery was calculated as 0% according to the concordance rate between bacteria isolated in drain tip culture and SSI cases. There was no correlation between the duration of suction drainage and the drain tip culture results or the onset of SSI within 72 hours. The results of suction drain tip culture could not reflect those of SSI regardless of the type of surgery (primary or revision), surgical region, surgical procedure, or implant use. CONCLUSION Drain tip culture in spinal surgery was not prognostic for SSI or helpful in detecting pathogenic bacteria for SSI. Routine use of drain tip culture when prophylactic antibiotics are used is not supported by the results of this study. LEVEL OF EVIDENCE 4.