# Antibiotic Treatment Practices and Microbial Profile in Diabetic Foot Ulcers: A Retrospective Cohort Study

## TL;DR

This study examines antibiotic use and infection patterns in diabetic foot ulcers, finding a mismatch between common bacteria and prescribed antibiotics.

## Contribution

The study identifies a mismatch between empiric antibiotic use and microbial profiles in diabetic foot ulcers, suggesting safer alternatives.

## Key findings

- Gram-negative bacteria were more common in infected diabetic foot ulcers than previously assumed.
- Vancomycin was overused despite low MRSA prevalence, increasing nephrotoxicity risks.
- Alternative antibiotics with less kidney toxicity are recommended for better treatment outcomes.

## Abstract

Aim and objective

Diabetic foot ulcers (DFUs) are a frequent complication of diabetes mellitus, impacting more than one in 10 diabetic patients, with roughly half of these ulcers progressing to infection. Existing literature indicates that these infections are predominantly polymicrobial, with gram-positive isolates being the most common. This microbial profile informs the empiric antibiotic strategies employed in first-world countries, often including highly potent nephrotoxic antibiotics. This retrospective cohort study aims to assess the microbial profile and antibiotic treatment practices in patients with infected DFUs at Ochsner LSU Health Shreveport Academic Medical Center in Shreveport, Louisiana, United States.

Materials and methods

A total of 115 patients diagnosed with infected DFUs were included in the study. Patient records were reviewed to identify bacterial pathogens cultured from foot wounds, antibiotic treatment regimens administered, and the prevalence of acute kidney injury (AKI).

Results

The study found a predominance of gram-negative isolates (199; 59.4%), facultative anaerobes (246; 73.4%), and polymicrobial infections (67; 78.8%) in infected DFUs. Vancomycin was administered to 95 patients (82.6%), with only a small number subsequently testing positive for methicillin-resistant Staphylococcus aureus (MRSA). Combination therapy with vancomycin and Zosyn was given to 71 patients (61.7%), which increased the potential risk of antibiotic-induced nephrotoxicity. AKI was prevalent, affecting 58 patients (50.4%).

Conclusions

This study highlights a discrepancy between the microbial profile of infected DFUs and empiric antibiotic treatment practices at Ochsner LSU Health Shreveport Academic Medical Center. The predominance of gram-negative bacteria underscores the need for a polymicrobial, gram-negative-focused empiric treatment approach. Alternative antibiotics with broad-spectrum coverage and minimal nephrotoxicity, such as ceftriaxone, clindamycin, metronidazole, amoxicillin-clavulanate, and linezolid, should be considered. Tailored antibiotic strategies, guided by local microbial profiles and patient-specific factors, are essential to optimize treatment outcomes in this high-risk population.