Epidemiology of diabetic foot infection in the Metro-Detroit area with a focus on independent predictors for pathogens resistant to recommended empiric antimicrobial therapy

Background. The polymicrobial nature of diabetic foot infection (DFI) and the emergence of antimicrobial resistance have complicated DFI treatment. Current treatment guidelines for deep DFI recommend coverage of methicillin-resistant Staphylococcus aureus (MRSA) and susceptible Enterobacteriaceae. This study aimed to describe the epidemiology of DFI and to identify predictors for DFI associated with multidrug-resistant organisms (MDROs) and pathogens resistant to recommended treatment (PRRT). Methods. Adult patients admitted to Detroit Medical Center from January 2012 to December 2015 with DFI and positive cultures were included. Demographics, comorbidities, microbiological history, sepsis severity, and antimicrobial use within 3 months before DFI were obtained retrospectively. DFI-PRRT was defined as a DFI associated with a pathogen resistant to both vancomycin and ceftriaxone. DFI-MDRO pathogens included MRSA in addition to PRRT. Results. Six-hundred forty-eight unique patients were included, with a mean age of 58.4 ± 13.7 years. DFI-MDRO accounted for 364 (56%) of the cohort, and 194 (30%) patients had DFI-PRRT. Independent predictors for DFI-PRRT included history of PRRT in a diabetic foot ulcer, antimicrobial exposure in the prior 90 days, peripheral vascular disease, and chronic kidney disease. Long-term care facility residence was independently associated with DFI due to ceftriaxone-resistant Enterobacteriaceae, and recent hospitalization was an independent predictor of DFI due to vancomycin-resistant Enterococcus. Conclusions. An unexpectedly high prevalence of DFI-PRRT pathogens was identified. History of the same pathogen in a prior diabetic foot ulcer and recent antimicrobial exposure were independent predictors of DFI-PRRT and should be considered when selecting empiric DFI therapy.