Objective To characterize and identify risk factors for 30-day surgical site infections (SSIs) in patients with head and neck cancer who underwent microvascular reconstruction. Study Design Cross-sectional study with nested case-control design. Setting Nine American tertiary care centers. Subjects and Methods Hospitalized patients were included if they underwent head and neck cancer microvascular reconstruction from January 2003 to March 2016. Cases were defined as patients who developed 30-day SSI; controls were patients without SSI at 30 days. Postoperative antibiotic prophylaxis (POABP) regimens were categorized by Gram-negative (GN) spectrum: no GN coverage, enteric GN coverage, and enteric with antipseudomonal GN coverage. All POABP regimens retained activity against anaerobes and Gram-positive bacteria. Thirty-day prevalence of and risk factors for SSI were evaluated. Results A total of 1307 patients were included. Thirty-day SSI occurred in 189 (15%) patients; median time to SSI was 11.5 days (interquartile range, 7-17). Organisms were isolated in 59% of SSI; methicillin-resistant Staphylococcus aureus (6%) and Pseudomonas aeruginosa (9%) were uncommon. A total of 1003 (77%) patients had POABP data: no GN (17%), enteric GN (52%), and antipseudomonal GN (31%). Variables independently associated with 30-day SSI were as follows: female sex (adjusted odds ratio [aOR], 1.6; 95% CI, 1.1-2.2), no GN POABP (aOR, 2.2; 95% CI, 1.5-3.3), and surgical duration ≥11.8 hours (aOR, 1.9; 95% CI, 1.3-2.7). Longer POABP durations (≥6 days) or antipseudomonal POABP had no association with SSI. Conclusions POABP without GN coverage was significantly associated with SSI and should be avoided. Antipseudomonal POABP or longer prophylaxis durations (≥6 days) were not protective against SSI. Antimicrobial stewardship interventions should be made to limit unnecessary antibiotic exposures, prevent the emergence of resistant organisms, and improve patient outcomes
