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Microbial isolates and their antimicrobial susceptibilities in inframalleolar foot infections
Neal R Barshes1, Maria C Rodriguez-Barradas, Carlos F Bechara
11 Michael E. DeBakey Department of Surgery, Baylor College of Medicine/Michael E. DeBakey Veterans Affairs Medical Center , Houston, Texas.
Background:
Foot infections are especially common among diabetic individuals and often contribute to limb loss. We investigated the microbiology of foot infections in our hospital to further understand the microbes involved and to assist in identifying potential empiric oral antibiotic regimens for foot infections.
Methods:
All moderate/severe inframalleolar foot infections that were drained surgically at a single center during a single calendar year were included. Initial isolates obtained intra-operatively were reviewed.
Results:
A total of 39 patients underwent operative drainage, of whom 34 (87%) had diabetes mellitus. Fifty-two total specimens were obtained, consisting of 26 fluid swabs, 12 soft-tissue specimens, and 11 bone specimens. Nineteen (49%) of the specimens were obtained from toe wounds, 16 (41%) from forefoot wounds, two (5%) from midfoot wounds, and two (5%) from heel wounds. Most specimens (71%) were polymicrobial, yielding a mean of 2.2 isolates. In all, 100 individual isolates, encompassing 39 different bacterial organisms, were identified (55 gram-positive aerobes, 33 gram-negative aerobes, 11 anaerobes, and one fungus). Enterococcus species and Staphylococcus aureus were the most common bacteria, each representing 13% of isolates. Only 9% of isolates were methicillin-resistant S. aureus. Obtaining multiple specimens (e.g., both fluid and tissue) increased the yield for identification of organisms. Oral antibiotics provided adequate coverage for gram-positive organisms but not for gram-negative organisms.
Conclusions:
Foot infections are typically polymicrobial and may involve a wide variety of microbes. Initial gram-stain results could be used to choose better initial empiric antimicrobial therapy for such infections.
Insights
Diabetic foot infections are often polymicrobial, involving diverse bacteria. Initial gram-stain results can guide empiric antibiotic selection for better treatment of these common, severe infections.
Area of Science:
- Infectious Diseases
- Microbiology
- Podiatry
Background:
- Diabetic foot infections are a significant cause of limb loss.
- Understanding the causative microbes is crucial for effective treatment.
- Identifying appropriate empiric oral antibiotic regimens is a clinical challenge.
Purpose of the Study:
- To investigate the microbiology of diabetic foot infections.
- To identify common bacterial and fungal organisms involved.
- To inform selection of empiric antibiotic therapy.
Main Methods:
- Surgical drainage of moderate to severe inframalleolar foot infections.
- Analysis of intra-operative isolates from 39 patients over one year.
- Review of specimen types, including fluid, soft tissue, and bone.
Main Results:
- 87% of patients had diabetes mellitus.
- Infections were frequently polymicrobial (71%), with a mean of 2.2 isolates per specimen.
- Enterococcus species and Staphylococcus aureus were the most common isolates (13% each).
- Oral antibiotics covered gram-positive but not gram-negative organisms adequately.
Conclusions:
- Diabetic foot infections are typically polymicrobial with diverse microbial profiles.
- Initial gram stain results can guide the selection of empiric antimicrobial therapy.
- Targeted antibiotic selection is essential for managing these complex infections.
