Epidemiology of Methicillin-Resistant Staphylococcus aureus Diabetic Foot Infections in a Large Academic Hospital: Implications for Antimicrobial Stewardship.

INTRODUCTION: Diabetic foot infections (DFIs) are the leading cause of non-traumatic lower extremity amputations in the United States. Antimicrobials active against methicillin-resistant Staphylococcus aureus (MRSA) are recommended in patients with associated risk factors; however, limited data exist to support these recommendations. Due to the changing epidemiology of MRSA, and the consequences of unnecessary antibiotic therapy, guidance regarding the necessity of empirical MRSA coverage in DFIs is needed. We sought to 1) describe the prevalence of MRSA DFIs at our institution and compare to the proportion of patients who receive MRSA antibiotic coverage and 2) identify risk factors for MRSA DFI. METHODS: This was a retrospective cohort study of all adult, culture-positive DFI patients managed at University Hospital, San Antonio, TX between January 1, 2010 and September 1, 2014. Patient eligibility included a principal ICD-9-CM discharge diagnosis code for foot infection and a secondary diagnosis of diabetes. The primary outcome was MRSA identified in the wound culture. Independent variables assessed included patient demographics, comorbidities, prior hospitalization, DFI therapies, prior antibiotics, prior MRSA infection, and laboratory values. Multivariable logistic regression was used to identify risk factors for MRSA DFI. RESULTS: Overall, 318 patients met inclusion criteria. Patients were predominantly Hispanic (79%) and male (69%). Common comorbidities included hypertension (76%), dyslipidemia (52%), and obesity (49%). S. aureus was present in 46% of culture-positive DFIs (MRSA, 15%). A total of 273 patients (86%) received MRSA antibiotic coverage, resulting in 71% unnecessary use. Male gender (OR 3.09, 95% CI 1.37-7.99) and bone involvement (OR 1.93, 1.00-3.78) were found to be independent risk factors for MRSA DFI. CONCLUSIONS: Although MRSA was the causative pathogen in a small number of DFI, antibiotic coverage targeted against MRSA was unnecessarily high.

Retrospective cohort study evaluating the incidence of diabetic foot infections among hospitalized adults with diabetes in the United States from 1996-2010.

BACKGROUND: The prevalence of diabetes has increased over the last 2 decades; however, the national incidence of diabetic foot infections (DFIs) in the United States is unknown. We sought to determine national trends in DFIs among hospitalized adults in the United States over 15 years. METHODS: This was a retrospective cohort study of the U.S. National Hospital Discharge Survey from 1996-2010. Adult patients with a principal diagnosis of foot infection and a secondary diagnosis of diabetes were identified using ICD-9-CM codes. Incidence was defined as DFI discharges per 100 diabetes discharges. Independent risk factors for DFI among diabetics were identified using multivariable logistic regression. RESULTS: These data represent 1,059,552 DFI discharges over the study period. The incidence of DFI decreased from 1996 (2.3 DFIs/100 diabetes discharges) to 2010 (1.1 DFI/100 diabetes discharges). The proportion of patients experiencing lower-extremity amputation declined from 33.2% in 1996 to 17.1% in 2010. Peripheral vascular disease (odds ratio [OR], 2.89; 95% confidence interval [CI], 2.87-2.91), peripheral neuropathy (OR, 2.62; 95% CI, 2.60-2.64), and male sex (OR, 1.67; 95% CI, 1.66-1.68) were the leading risk factors for DFI. CONCLUSION: The incidence of DFI among hospitalized adults in the United States declined by more than half from 1996-2010.