Bacterial Profile and Antimicrobial Resistance in Diabetic Foot Ulcer Infections: A 10-Year Retrospective Cohort Study

Research Type: Level 3 - Retrospective cohort study, Case-control study, Meta-analysis of Level 3 studies Introduction/Purpose: Diabetic foot infections (DFI) are severe complications of diabetes, often leading to prolonged hospitalizations and amputations. Approximately 15% of diabetic patients will develop foot ulcers during their lifetime, with many progressing to chronic infections and osteomyelitis. Inappropriate antibiotic use promotes biofilm formation and the selection of multidrug-resistant bacteria, increasing morbidity and treatment costs. While Gram-positive cocci, particularly staphylococci, are frequently isolated, Gram-negative bacteria such as Proteus mirabilis and Enterobacter cloacae are also prevalent. Antimicrobial resistance in DFI significantly impacts clinical management, highlighting the need for a detailed understanding of local microbiological profiles. This study aims to identify the main pathogens associated with diabetic foot infections and evaluate their antibiotic resistance patterns over a decade. Methods: This retrospective cohort study assessed diabetic patients undergoing surgical treatment for infected diabetic foot ulcers at a private tertiary hospital in Brazil between 2013 and 2022. Patients diagnosed with foot infections secondary to ulcers and undergoing surgical procedures were included. Demographic data, amputation levels, and microbiological results were extracted from electronic medical records. Cases with incomplete data were excluded. Samples were analyzed using standardized protocols to identify bacterial species and antimicrobial resistance patterns. Statistical analysis included frequency distribution and normality tests. The sample size was estimated at 377 patients with a 95% confidence level and a 5% margin of error. Results: A total of 459 diabetic patients were analyzed, of whom 337 had positive cultures, yielding 507 samples. The mean age was 66.4 years (SD: 13.8), and 69.1% were male. The most common procedures were minor amputations (53.5%) and debridements (36.0%). Gram-negative bacteria accounted for 55.2% of isolates, with Proteus sp. (10.3%) and Escherichia coli (8.3%) being the most prevalent. ESBL resistance was 15.4%, and quinolone resistance reached 29.3%. Among Gram-positive cocci (43.6%), Staphylococcus aureus (16.8%) showed 21.1% methicillin resistance, while Enterococcus sp. exhibited 7% vancomycin resistance. Multidrug-resistant organisms were found in 16% of Pseudomonas sp. and 63.6% of Acinetobacter sp. These findings highlight the need for targeted antimicrobial protocols to optimize treatment and reduce morbidity. Conclusion: The predominance of Gram-negative bacteria and high antimicrobial resistance rates emphasize the importance of continuous microbiological surveillance in DFI management. The identification of multidrug-resistant organisms, particularly Acinetobacter sp. and Pseudomonas sp., limits therapeutic options and necessitates targeted antimicrobial strategies. This study underscores the need for updated institutional protocols to optimize empirical therapy and reduce complications. Infection control measures and judicious antibiotic use are crucial for improving clinical outcomes in diabetic patients with infected ulcers, preventing progression to amputations and prolonged hospitalizations. Resistance of microorganisms isolated from surgical cultures in diabetic foot infections The bar chart illustrates the distribution of antibiotic resistance among the isolated bacteria. The majority of isolates were susceptible (gray), but significant resistance was observed, including ESBL-producing bacteria (yellow), carbapenem-resistant strains (blue), sulfonamide resistance (orange), MRSA (Staphylococcus aureus resistant to methicillin, red), vancomycin-resistant Enterococcus sp. (green), and penicillin/ceftriaxone-resistant Streptococcus sp. (purple). These findings emphasize the prevalence of multidrug-resistant organisms in diabetic foot infections.