Study on the Microbiological Characteristics of Infection in Diabetic Foot Ulcers (Wagner Grades 2-4) and Their Impact on Outcomes

Objective To evaluate the influence of microbiological characteristics on Wagner grade and 12-month outcomes in hospitalized patients with Wagner grade 2–4 diabetic foot ulcers (DFUs). Methods This single-center retrospective cohort included 205 culture-positive infected DFUs with complete 12-month follow-up. Grade 4 was the severity outcome; nonhealing/readmission was adverse. Associations between each major organism and Wagner grade 4 were assessed using hierarchical logistic regression with sequential adjustment for host characteristics, HbA1c and WBC, and CRP, PCT, and ESR. Results were interpreted jointly across models, with Benjamini–Hochberg correction applied to the 11 organism-specific tests within each model. Results Grades 2/3/4 comprised 49/59/97 patients; 162 healed, 22 were unhealed, and 21 readmitted. Staphylococcus aureus was most frequent but not robustly associated. Of 19 Enterococcus -positive patients, 16 had grade 4. Enterococcus detection showed a positive association with grade 4 after adjustment for host characteristics, HbA1c, and WBC count (OR, 8.02; 95% CI, 2.11-30.46; q = 0.024). After additional adjustment for CRP, PCT, and ESR, the estimate remained positive but was attenuated (OR, 5.27; 95% CI, 1.16-23.89; raw P = 0.031) and did not meet the prespecified false-discovery-rate criterion (q = 0.172). No individual organism was robustly associated with the composite adverse outcome. Compared with one organism, two and ≥3 organisms yielded ORs 2.50 (95% CI, 1.09-5.72) and 4.89 (95% CI, 1.40-17.11); ≥3 organisms remained associated in sensitivity analysis (OR, 5.02; 95% CI, 1.42-17.76). Conclusions Among hospitalized patients with culture-positive Wagner grade 2–4 DFUs, Staphylococcus aureus was most common but showed limited independent associations with severity or 12-month outcomes. Enterococcus spp. clustered in grade 4 wounds, although its independent association was inconsistent across adjusted models. Detection may mark severe wound complexity but should not independently guide grading or treatment. Detection of ≥3 organisms was associated with increased risk of the 12-month composite adverse outcome, but the imprecise estimate requires prospective multicenter validation.