Association between the duration of diabetes and gram-negative bacterial infection in diabetic foot infections: a case-control study

This retrospective case-control study was designed to explore the association between the duration of diabetes and gram-negative bacterial infection in diabetic foot infections (DFIs). All DFI patients hospitalized in the Department of Endocrinology in the Sixth Affiliated Hospital of Sun Yat-sen University between 2013 and 2019 with positive microbial culture results were included. Cases were defined as DFI patients whose microbial cultures grew gram-negative bacteria (including polymicrobial flora). Controls were defined as DFI patients whose positive microbial cultures did not grow gram-negative bacteria. Clinical data were extracted from the hospital information system. Stabilized inverse probability weighting was used to balance between-group differences at baseline. Confounders were selected using a directed acyclic graph. Missing data were imputed with the multiple imputation of chained equations method. Odds ratios (ORs) with 95% confidence intervals (CIs) and P_trend for associations between the duration of diabetes and gram-negative bacterial infection were obtained using binomial logistic regression models. The weighted OR of gram-negative bacterial infection for DFI patients with a moderate duration of diabetes (8~19 years) compared with those with a short duration (0~7 years) was 3.87 (95% CI: 1.15 to 13.07), and the OR for those with a longer duration (20~30 + years) was 7.70 (95% CI: 1.45 to 41.00), and there was a dose-response trend with increasing duration of diabetes (weighted P_trend = 0.007). The results demonstrated that a long duration of diabetes might be associated with an increased risk of gram-negative bacterial infection in type 2 diabetes patients with DFI.