NSTI Organisms and Regions: A Multicenter Study From the American Association for the Surgery of Trauma

Background: Conflicting data on the microbiology and epidemiology of necrotizing soft tissue infections (NSTIs) appear to stem from the heterogeneity in microbiology observed in regions across the United States. Our goal was to determine current differences in organism prevalence and outcomes for NSTI and non-necrotizing severe soft tissue infections across the United States. We hypothesized that there were geographical differences in organism prevalence that would lead to differences in outcomes. Materials and Methods: This study was a retrospective multi-institutional trial from centers across the United States and Canada. Demographic, clinical, and outcomes data were collected. Bivariate and multivariable analyses were performed to determine the effects of region and microbiology on outcomes. Results: A total of 622 patients were included in this study. Polymicrobial infections (45%) were the most prevalent infections in all regions. On bivariate analysis, Clostridium and polymicrobial infections had higher mean Laboratory Risk Indicator for Necrotizing Fasciitis scores and American Association for the Surgery of Trauma grades (P < 0.001 for both) than other organisms. Patients in the South were more likely to be uninsured and had worse unadjusted outcomes. In a risk-adjusted model, increasing American Association for the Surgery of Trauma grade was predictive of mortality (OR, 2.3; 95% CI, 1.6–3.1; P < 0.001), as was age ≥ 55 y (OR 2.7, 95% CI 1.3–5.3, P = 0.006), but region and organism type were not associated with mortality. Conclusions: We found important regional differences with respect to organism type and demographics. However, on risk-adjusted models, neither region nor organism type predicted mortality.