Characterization of Necrotizing Soft Tissue Infections in Obese and Non-Obese Patients.

Background: The impact of obesity on the pathogenesis and prognosis of necrotizing soft tissue infections (NSTIs) is unclear. The goal of this study was to characterize differences in NSTI presentation and outcomes by obesity status. Patients and Methods: A retrospective analysis of institutional data for patients diagnosed with NSTIs were identified (n = 619; 2011-2020). Patients were divided based on obesity (body mass index [BMI] ≥ 30 kg/m2) and non-obese (BMI <30 kg/m2). Primary outcomes included NSTI location, micro-organisms, and index hospitalization data. Multiple logistic regression was used to model predictors of in-hospital and 90-day mortality. Results: The obese cohort (n = 390; 63%) had higher rates of congestive heart failure and type 2 diabetes mellitus. There were no differences in length of stay, mortality, or discharge disposition between groups. A higher rate of respiratory failure was observed in the obese versus non-obese group (36.7% vs. 20.9%; p < 0.0005). The obese cohort was associated with perineal (40.8% vs. 27.0%) and torso NSTIs (20.9% vs. 15.8%; p < 0.005) but reduced staphylococcal (19.2% vs. 27.4%; p = 0.02) and group A streptococcal (2.6% vs. 6.5%; p = 0.03) infections, and increased polymicrobial infections. Class 2 obesity was a negative predictor for in-hospital mortality (odds ratio [OR], 0.1; 95% confidence interval [CI], 0.03-0.5) and 90-day mortality (OR, 0.3; 95% CI, 0.1-0.8), when adjusting for demographic data, type of infection, and baseline comorbidities. Conclusions: Necrotizing soft tissue infections in obesity may present with unique distributions and microbial characteristics. Class 2 obesity may exhibit a survival benefit compared with non-obese patients, suggestive of an obesity paradox.