Serum Interleukin-6, Tumour Necrosis Factor-α and Lipopolysaccharide-binding Protein in Pseudomonas aeruginosa-Associated Diabetic Foot Ulcers: A Cross-sectional Study of Clinical, Microbiological and Inflammatory Profiles from Al-Najaf, Iraq

Abstract

Background: Pseudomonas aeruginosa is frequently isolated from infected diabetic foot ulcers (DFUs), but whether its recovery is associated with a distinct systemic inflammatory profile remains uncertain. This study compared serum interleukin-6 (IL-6), tumour necrosis factor-α (TNF-α) and lipopolysaccharide-binding protein (LBP) in patients with and without P. aeruginosa-associated DFUs and in healthy adults. Methods: This cross-sectional study included 120 participants in Al-Najaf, Iraq: 40 patients with clinically infected DFUs yielding P. aeruginosa, 40 with infected DFUs without P. aeruginosa and 40 healthy controls. Bacterial isolates underwent disc-diffusion susceptibility testing, and serum biomarkers were measured by ELISA. Analyses adjusted for age, sex and body-mass index. Results: Mean IL-6, TNF-α and LBP concentrations were higher in P. aeruginosa-positive than P. aeruginosa-negative DFUs (26.7 vs 16.5 pg/mL, 100.1 vs 59.1 pg/mL and 14.1 vs 10.9 µg/mL, respectively; all P < 0.001), with lower values in healthy controls. Twenty of 40 P. aeruginosa isolates were multidrug resistant, although biomarker concentrations did not differ significantly by resistance status. LBP (AUC 0.946) and TNF-α (AUC 0.941) discriminated P. aeruginosa-positive from P. aeruginosa-negative DFUs better than C-reactive protein (AUC 0.812). LBP was the only independent correlate of P. aeruginosa isolation. Conclusion: P. aeruginosa-positive DFUs were associated with a greater systemic inflammatory response. LBP showed the strongest discriminatory performance, but external validation is required before clinical application.