Routine intraoperative microbiological smear testing in patients with reoperation after elective degenerative non-instrumented spine surgery–useful or negligible adjunct

Surgical site infections (SSI) are a rare but dreaded cause for recurrent symptomatology requiring reoperation after degenerative spine surgery. We here aim to elucidate if routine microbiological smear testing during reoperation might be a useful tool for subsequent patient management.

We investigated clinical, laboratory/imaging characteristics, and outcome of patients undergoing reoperation in the previously affected segment during follow-up after elective degenerative non-instrumented spine surgery. Microbiological cultures via multiple intraoperative smear tests of the superficial/deep wound layers were routinely performed and correlated with clinical/imaging/laboratory/surgical signs for SSI and outcome.

From altogether 2552 patients with degenerative spine surgery in 2014–2019, a total of 62 patients (m:f = 1.6:1, median 69 years) underwent same-level reoperation due to recurrent symptomatology (mean ∆-time:17 ± 36 months) with a predominance of the lumbar spine (90%). In 9 patients with imaging/laboratory suspicious for SSI, microbiological culturing of intraoperative smear testing revealed conclusive pathogen growth in 89% (100% with additional PCR analysis); the predominant pathogen was Staphylococcus aureus with detection mainly in the deep wound layers. In contrast, in 53 patients without clinical/imaging/laboratory/intraoperative signs for SSI microbiological culturing showed minor pathogen growth in 15% displaying bacterial colonization/contamination of the surgical site. The predominant pathogens in this cohort were Staphylococcus epidermidis and Cutibacterium acnes, and these patients had favorable outcomes when monitored with close surveillance without anti-infective treatment.

Bacterial colonization/contamination occurs in 15% of patients without signs of infection undergoing same-level reoperation after degenerative spine surgery. These patients can be managed with close surveillance without antibiotic treatment.