GRAM-NEGATIVE TOE WEB INFECTION

Gram-negative toe web infection (GNTWI) is an uncommon bacterial infection of the web spaces, usually precipitated the constant wearing of shoes.

Males predominate with a ratio of 4:1.
In a review of 123 cases, Pseudomonas aeruginosa was the prevailing pathogen, but E. coli, Proteus mirabilis, and Morganella morganii were also found. (Of note, gram-negative bacteria can be cultured in 10% of normal appearing web spaces.)
Interdigital tinea commonly predisposes primarily by two mechanisms: 1) Damage to the stratum corneum facilitating bacterial invasion and 2) Secretion of penicillin and streptomycin-like antibacterial substances favoring colonization by gram-negative bacteria.
Chronically wet feet is a risk factor. This is usually via the chronic wearing of shoes and the profession e.g., coal miners; or occasionally hyperhidrosis.

Clinical

Initially, the toe web becomes white and macerated. Later, wetness, inflammation, and odor develops. In the full-blown setting, the web spaces of all toes are eroded, malodorous, and inflamed. Green-tinted pus and/or even skin may be seen. The web spaces may fluoresce under Wood's light.

Treatment

A bacterial culture should be done, but ciprofloxacin (e.g. 500 mg BID) or another antibiotic with activity against gram-negative bacteria should be started before the results are available. Ideally, the patient should not wear shoes until healing has occurred. Vinegar soaks twice or three times a day should be done to reduce the bacterial load and to dry out the feet. Towel drying or preferably blow-drying after water contact is recommended. Ciclopirox olamine (BID, fluid or gel) has been recommended as the best single topical agent, owing to its antifungal, antibiotic (especially Gram-negative spectrum) and anti inflammatory properties. Alternatively, topical gentamicin (e.g., Garamycin) can be quite helpful. Many patients need time off work. The patient needs close followup during the healing process. After several days of antibiotics and drying out the feet, a topical steroid ointment may need to be added as eczematous changes of the feet are very common.

Debridement of any hyperkeratotic rim may promote healing (local anesthetic usually necessary).

Once the initial inflammatory condition has been cleared, the feet, and especially the nails, should be studied for the presence of dermatophyte infection. If onychomycosis is present, it should be treated to prevent recurrence. Long term, keeping the feet as dry as possible is key, e.g., avoid prolonged wearing of shoes, treat any hyperhidrosis, blow-dry after shower, powders, etc.

Additional Photographs

Gram negative toe web infection with Id Reaction.

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