What is the treatment for bacterial overgrowth of the feet?

Treatment of Bacterial Overgrowth of the Feet

For bacterial overgrowth of the feet (interdigital athlete's foot with bacterial superinfection), the primary treatment is aggressive drying measures combined with broad-spectrum topical antimicrobials, as bacterial suppression is essential for symptom resolution. 1

Understanding the Pathophysiology

Bacterial overgrowth of the feet typically begins with dermatophyte invasion of the skin, followed by moisture accumulation that stimulates bacterial proliferation 1:

• Aerobic diphtheroids cause the common wet, macerated presentation between the toes 1
• Gram-negative organisms (Pseudomonas, Proteus) are responsible for more severe cases with pronounced maceration and odor 1
• The condition alternates between dry, scaly phases and wet, macerated phases depending on moisture levels 1

Primary Treatment Algorithm

Step 1: Aggressive Drying (Most Critical)

Drying is the decisive element in treatment 1:

• Expose feet to air by wearing sandals or open-toed shoes to enhance water evaporation 1
• Apply aluminum chloride topically, which provides both broad-spectrum antimicrobial activity and chemical drying 1
• Change socks daily and avoid tight shoes that trap moisture 2
• Thoroughly dry between toes after showers 2

Step 2: Topical Antimicrobial Therapy

For the bacterial component 1, 3:

• Aluminum chloride is the agent of choice, combining broad-spectrum antibacterial activity with drying properties 1
• Topical antibiotics with broad-spectrum coverage against both aerobic and gram-negative bacteria 1
• Newer imidazoles have broad-spectrum activity but limited effectiveness against gram-negative organisms 1

Step 3: Address Underlying Fungal Infection

Once bacterial overgrowth is controlled, treat the underlying dermatophyte infection 3, 4:

• Topical allylamines (e.g., terbinafine 1% cream daily for 1 week) with 94% mycological cure rate 2
• Ciclopirox olamine 0.77% cream or gel applied twice daily for 4 weeks achieves ~60% cure rate at end of treatment and 85% two weeks post-treatment 2
• Topical azoles (clotrimazole 1% twice daily for 4 weeks) are effective alternatives 2

Step 4: Consider Oral Therapy for Severe or Refractory Cases

Oral antifungals are indicated for extensive infections, vesicobullous type, moccasin foot, or in diabetic/immunosuppressed patients 3, 5:

• Terbinafine 250 mg once daily for 1 week has similar efficacy to 4 weeks of topical clotrimazole but with faster clinical resolution 2
• Itraconazole 100 mg once daily is an alternative with comparable efficacy 2

Special Populations

Diabetic Patients

For diabetic patients with bacterial foot infections, more aggressive management is required 6, 7:

• Mild infections: Amoxicillin-clavulanate as first-line oral therapy 6
• Moderate-to-severe infections: Consider parenteral therapy with piperacillin-tazobactam 3.375g IV every 6 hours 6
• Obtain wound cultures before starting antibiotics 6
• Ensure appropriate wound debridement and pressure off-loading 6
• Obtain urgent surgical consultation for deep infections, abscesses, or necrotizing infection 2

Prevention Strategies

Foot powder application after bathing reduced tinea pedis rates from 8.5% to 2.1% over 3.5 years, primarily by reducing T. mentagrophytes from 5.3% to 0.5% 2:

• Apply antifungal powder daily after bathing 2
• Wear sandals in communal shower and locker rooms 2, 8
• Change socks daily 2
• Periodically clean athletic footwear 2

Important Caveats

• Permanent eradication is unlikely in shoe-wearing populations in temperate climates, as fungal reservoirs in nails and soles ensure reinfection 1
• This is mainly a seasonal disease with hot-weather exacerbations requiring preventive measures 1
• Flare-ups are experimentally induced by occlusion of fungus-infected feet, emphasizing the critical role of moisture control 1
• Treatment focuses on preventing or ameliorating seasonal exacerbations rather than permanent cure 1