UC San Diego

Background

Diabetic foot infections (DFIs) are commonly associated with antibiotic overuse. Empiric DFI treatment often includes coverage for Pseudomonas aeruginosa (PsA), but the frequency of PsA DFIs is poorly understood. The study objectives were to quantify the prevalence of and determine predictors for PsA DFIs.

Methods

This multicenter, retrospective cohort included hospitalized patients with DFI from 2013 through 2020 who were age ≥18 years; diabetes mellitus diagnosis; and DFI based on International Classification of Diseases, Tenth Revision coding, antibiotic treatment, and DFI culture with organism growth. Osteomyelitis was excluded. Patient characteristics were described and compared; the primary outcome was presence of PsA on DFI culture. Predictors of PsA DFI were identified using multivariable logistic regression.

Results

Two hundred ninety-two patients were included. The median age was 61 (interquartile range [IQR], 53-69) years; the majority were men (201 [69%]) and White (163 [56%]). The most commonly isolated organisms were methicillin-susceptible Staphylococcus aureus (35%) and streptococci (32%); 147 (54%) cultures were polymicrobial. Two hundred fifty-seven (88%) patients received empiric antibiotics active against PsA, but only 27 (9%) patients had PsA DFI. Immunocompromised status (adjusted odds ratio [aOR], 4.6 [95% confidence interval {CI}, 1.3-16.7]) and previous outpatient DFI antibiotic treatment failure (aOR, 4.8 [95% CI, 1.9-11.9]) were associated with PsA DFI.

Conclusions

PsA DFI is uncommon, but most patients receive empiric antipseudomonal antibiotics. Empiric broad-spectrum antibiotics are warranted given the frequency of mixed infections, but patient-specific risk factors should be considered before adding antipseudomonal coverage.