Chronic Kidney Disease Differentially Affects Microbial Patterns, Antimicrobial Sensitivity, and Outcomes in Diabetic Foot Infections

OBJECTIVE Renal function–stratified data on deep tissue/bone microbiology, antimicrobial resistance, and outcomes in diabetic foot infection (DFI) are limited. We compared bacterial isolates, antimicrobial resistance patterns, and outcomes in DFI with chronic kidney disease (CKD) versus preserved kidney function. RESEARCH DESIGN AND METHODS In this retrospective cohort study, adults with type 2 diabetes and clinically infected foot ulcers undergoing debridement with deep soft tissue and/or bone biopsy were grouped as CKD (estimated glomerular filtration rate [eGFR] <60 mL/min/1.73 m2) or non-CKD (eGFR ≥60 mL/min/1.73 m2). Standard aerobic/anaerobic cultures and antimicrobial susceptibility testing were performed. Resistance was categorized as multidrug resistant (MDR), extensively drug resistant (XDR), pandrug resistant (PDR), and MDR composite (MDR/XDR/PDR). The outcomes included wound healing, lower-extremity amputation, and death. RESULTS Among 726 patients, 888 specimens (622 soft tissue, 266 bone) yielded 852 isolates. Gram-negative organisms predominated in both groups. However, bone specimens from the CKD group had a higher proportion of gram-positive isolates than the non-CKD group (45.1% vs. 31.9%; P = 0.01). In soft tissue isolates, the CKD group had higher XDR (21.0% vs. 12.4%; P = 0.007) and MDR composite (46.3% vs. 31.0%; P = 0.0003) rates. In bone isolates, the CKD group had higher MDR (24.2% vs. 10.0%; P = 0.003) and MDR composite (46.2% vs. 23.8%; P = 0.0004) rates. Outcomes were poorer in the CKD group, with lower healing (78.4% vs. 85.0%; P = 0.02) and higher mortality (5.0% vs. 1.3%; P = 0.002). CONCLUSIONS DFI in CKD is associated with a higher burden of difficult-to-treat, MDR microbial phenotypes (MDR, XDR, and MDR composite), contributing to poor clinical outcomes compared with DFI with preserved renal function. The higher resistance burden and low soft tissue–bone concordance support early deep tissue or bone culture and culture-guided treatment refinement.