Treating Secondary Infection In A Patient With Severe Tinea Pedis

Author(s): 
Michael Moharan, DPM, Mohamed Abdelmegeed Ahmed, MD, DPM, and Oleg Karpenko, MD, DPM

* A Wood light examination of a pseudomonal toe web reveals a green-white fluorescence from the elaboration of pyoverdin.

* A computed tomography scan of soft tissue and bone of skin infections may be required to exclude an abscess formation or osteomyelitis.

Key Treatment Considerations

Treatment of Pseudomonas infections entails the use of antimicrobial agents.10 Anti-pseudomonal drug combination therapy (such as a beta-lactam antibiotic with an aminoglycoside) is usually recommended for the initial empiric treatment of a pseudomonal infection, especially for patients with neutropenia, bacteremia, sepsis, severe upper respiratory infection or abscess formation. The choice of antibiotic also depends on the site and extent of infection, and on local antibiotic resistance patterns.

   Reports of more resistant strains of Pseudomonas organisms to the currently used antimicrobials are causing much concern.11B. cepacia has grown resistant to aminoglycosides, anti-pseudomonal penicillins and most beta-lactam agents. Some strains are variably susceptible to third-generation cephalosporins, ciprofloxacin (Cipro, Bayer), trimethoprim-sulfamethoxazole (Septra, GlaxoSmithKline), ampicillin-sulbactam (Unasyn), chloramphenicol (Neogen) or meropenem (Merrem, AstraZeneca).12

   Since human cases of glanders are rare, limited information is available about antibiotic treatment of the organism in humans. Sulfadiazine has been effective in experimental treatments of animals and humans. B. mallei organisms are usually sensitive to tetracyclines, ciprofloxacin, streptomycin, novobiocin, gentamicin, imipenem (Primaxin, Merck), ceftazidime (Fortaz, GlaxoSmithKline) and sulfonamides. Researchers have reported resistance to chloramphenicol.12 Treatment duration is often prolonged, from one to two months, and clinicians often combine this with surgical drainage.

   Ceftazidime alone or in combination with either trimethoprim-sulfamethoxazole or amoxicillin clavulanate is the therapy of choice for B. pseudomallei.12 The organism is usually sensitive to imipenem, penicillin, doxycycline (Adoxa, PharmaDerm), azlocillin, ceftazidime, ticarcillin-clavulanic acid (Timentin, GlaxoSmithKline) and ceftriaxone (Rocephin, Hoffmann-La Roche). Initiate treatment early in the course of the disease. The organism is resistant to ciprofloxacin and aztreonam (Azactam, Bristol-Myers Squibb). Treatment is often prolonged, from three to 12 months, with the longest duration of therapy used for chronic extrapulmonary disease.

   Management of pseudomonal cellulitis includes the use of a PO antibiotic for seven to 10 days. This often resolves a localized infection.

   Pseudomonal toe web infections require initial debridement with applications of silver nitrate or 5% acetic acid to the toe webs and the dorsal and plantar areas. Following this initial treatment, apply a topical antibiotic, silver sulfadiazine cream or Castellani paint until infection resolves. A PO quinolone effectively reduces the duration of infection.

   Pseudomonal folliculitis is often "self-limiting." Treatment may require only application of silver sulfadiazine cream or 5% acetic acid wet compresses for 20 minutes two to four times daily with topical antibiotics.

In Conclusion

Interdigital toe web space is a warm, moist, protected environment that predisposes to the proliferation of both dermatophytes and gram-negative organisms. Tinea pedis is by far the most common fungal infection. Maceration, scaling and fissures result, allowing for overgrowth of bacteria that normally inhabit this interspace. Proliferation of these organisms, which include, most prominently, Pseudomonas aeruginosa, other gram-negative bacteria (e.g., Escherichia coli and Proteus mirabilis) and gram-positive bacteria, leads to an aggressive, painful infection.

Comments

I have seen patients with Pseudomonas aeruginosa infection secondary to interdigital fungi infection. Instead of using topical cream, I use silver dressing with exudate control ability such as Aquacel Ag or Acticoat with aligiste m, together with oral antibiotics. The infected toe webs dried up, became less swollen and the foot healed up within two weeks.

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