251. Risk Factors for Pseudomonas aeruginosa in Diabetic Foot Infections
Session: Poster Abstract Session: Clinical: Skin and Soft Tissue
Thursday, October 5, 2017
Room: Poster Hall CD
Background: Infectious Diseases Society of America guidelines for the management of diabetic foot infections (DFIs) suggest 15 different antibiotic treatment options for moderate-to-severe infections. All treatment options provide coverage for gram-positive cocci, and some provide coverage for gram-negative pathogens, including Pseudomonas aeruginosa (PSA). However, there is minimal guidance in determining which patients require anti-PSA therapy.


This single-center retrospective case-control study included patients hospitalized between October 2013-September 2015. Adult patients admitted with a DFI were identified using a combination of ICD-9 codes for diabetes with complications and cellulitis. The primary outcome was identification of risk factors associated with PSA DFIs. A multivariable model using logistic regression was constructed, and a receiver operator characteristic (ROC) curve was generated to assess the sensitivity and specificity of the model.

Results: 262 patients were included and 12 (4.6%) patients had cultures with PSA. Multivariable analysis yielded six risk factors for PSA DFIs (see table). ROC construction yielded an area under the curve of 0.895.

Conclusion: The incidence of PSA from DFIs is low. A model with excellent performance characteristics demonstrated that risk factors for PSA DFIs include age > 65, BMI ≥ 35, former or current smoker, history of lower extremity bypass procedure, and cardiovascular disease. Future validation of these factors could help stewardship programs reduce unnecessary antibiotic utilization.

Risk Factor for PSA DFI

Odds Ratio (95% confidence interval)


Age > 65 years

5.94 (1.40-25.28)


Body mass index ≥ 35 kg/m2

7.53 (1.73-32.81)


Former or current smoker

9.27 (1.06-81.54)


History of a lower extremity bypass procedure

9.63 (1.52-61.15)


Cardiovascular disease

5.28 (1.22-22.86)


Severe infection

4.50 (0.97-20.95)


Nada Farhat, PharmD, Michigan Medicine, Ann Arbor, MI, Daniel McClung, MD, Internal Medicine, University of Michigan, Ann Arbor, MI and Jerod Nagel, PharmD, BCPS, Department of Pharmacy, Michigan Medicine, Ann Arbor, MI


N. Farhat, None

D. McClung, None

J. Nagel, None

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