Obesity is not associated with antimicrobial treatment failure for intra-abdominal infection

Zachary Dietch, University of Virginia Health System; Puja M. Shah, University of Virginia Health System; Brandy Edwards, University of Virginia Health System; Stephen Davies, University of Virginia Health System; Christopher Guidry, University of Virginia Health System; Robert Sawyer, University of Virginia Health System

Obesity and commonly associated comorbidities are known risk factors for the development of infections. However, the intensity and duration of antimicrobial treatment are rarely conditioned on body mass index (BMI). In particular, the influence of obesity on failure of antimicrobial treatment for intra-abdominal infection (IAI) remains unknown.

We hypothesized that obesity is associated with recurrent infectious complications in patients treated for IAI.

518 patients randomized to treatment in the Surgical Infection Society Study to Optimize Peritoneal Infection Therapy (STOP-IT) trial were evaluated. One patient was excluded from analysis because of missing data. Patients were stratified by obese (BMI≥35) versus non-obese (BMI˂35) status. Descriptive comparisons were performed using Chi-square, Fisher’s exact, and Wilcoxon rank-sum tests as appropriate. Multivariate logistic regression using a priori selected variables was performed to assess the independent association between obesity and treatment failure in patients with IAI.

Overall, 100 (19.3%) of patients were obese (BMI≥35) versus 417 (80.7%) who were non-obese. Mean antibiotic days and total hospital days were similar between both groups. Unadjusted outcomes of surgical site infection (10.0% vs. 7.2%, p=0.35), recurrent intra-abdominal infection ((15.0% vs. 14.6%, p=0.92), death (2.0% vs. 0.7%, p=0.25), and a composite of all complications (25.0% vs. 21.0%, p=0.40) were also similar between both groups. After controlling for appropriate demographics, comorbidities, severity of illness, treatment group, and duration of antimicrobial therapy, obesity was not independently associated with treatment failure (c-statistic: 0.70) (Table)

Obesity is not associated with antimicrobial treatment failure among patients with IAI. These results suggest that obesity may not independently influence the need for longer duration of antimicrobial therapy in treatment of IAI versus non-obese patients.

Table 1. Results of Multivariate Regression Evaluating Obesity as Risk Factor for IAI Treatment Failure