Gram-Negative Toe Web Infection Workup

Updated: Mar 26, 2021
  • Author: Robert A Schwartz, MD, MPH; Chief Editor: William D James, MD  more...
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Laboratory Studies

To determine the etiologic agents, bacterial culturing and sensitivity testing, potassium hydroxide preparation, and fungal culturing should be performed. Some of the gram-negative organisms isolated and identified on Gram staining and/or culturing include P aeruginosa, Proteus mirabilis, and Enterococcus species. Usually, patients are infected by more than one organism. Some other organisms found on gram-negative cultures include Serratia marcescens, Escherichia coli, alpha streptococci, Proteus vulgaris, and Enterobacter species. Fungal culturing can be used to isolate a fungus associated with the infection, whether it is a dermatophyte or a yeast.

A patient's immune status may need to be evaluated, especially if response to therapy is slow, because serious potentially lethal systemic complications may occur. In addition, complete blood cell counts with differential and fasting blood glucose levels may be used to screen the patient's immune status and to exclude diabetes mellitus.

A Wood light examination and culture should be performed to establish the diagnosis of Pseudomonas toe web infection.


Histologic Findings

Histologically, an eroded epidermis is anticipated, sometimes with a serous or serosanguineous exudate at its base, with numerous neutrophils and scattered bacteria.

The infection can begin primarily as a typical tinea pedis infection, but it can escalate and become severe, manifesting erythema and erosions and extending beyond the toes.