Does antimicrobial homogeneity index influence surgical site infection? A 10-year study in lung, breast, and general surgery

To address whether hospital antimicrobial use influences surgical site infection (SSI), we investigated factors including antimicrobial homogeneity index (AHI), an indicator of prescription diversity, with a retrospective study during 120 months for patients undergoing lung, breast, and general surgery (n = 4,510). We analyzed the odds ratios of background factors for SSI and the correlation between AHI and drug susceptibility in isolates of SSI. A total of 243 cases of SSI (5.4%) occurred. Factors that significantly contributed for SSI were operative time [odds ratio (OR), 1.78; 95% confidence interval (CI), 1.33–2.39; P < 0.001], American Society of Anesthesiologists’ score (OR, 1.68, 95% CI, 1.23–2.28; P < 0.001), endoscopic use (OR, 0.10, 95% CI, 0.04–0.24; P < 0.001), lung and breast surgery versus general surgery (OR, 0.12, 95% CI, 0.06–0.22; P < 0.001), increased AHI (OR, 0.72, 95% CI, 0.55–0.95; P = 0.020), and older age (OR, 2.08, 95% CI, 1.39–3.11; P < 0.001). AHI showed a positive correlation coefficient (CC, P < 0.05) with susceptibility to ampicillin (CC = +0.327), cefotaxime (CC = +0.142), imipenem/cilastatin (CC = +0.101), and sulbactam/cefoperazone (CC = +0.145). AHI, which has been described to help prevent drug resistance, was associated with increased susceptibility in microbes of SSI. This finding in part may explain that increase in AHI reduced SSI.