What bacteria are of concern in a penetrating wound through the sole of a shoe?

Bacteria of Concern in Penetrating Wounds Through Shoe Soles

Penetrating wounds through the sole of a shoe are most commonly infected with Staphylococcus aureus and Pseudomonas aeruginosa, with Pseudomonas being particularly concerning due to its association with osteomyelitis following puncture wounds through footwear.

Primary Pathogens by Wound Type

Immediate Concerns (Acute Infection)

• Pseudomonas aeruginosa: Most critical pathogen in puncture wounds through shoe soles 1

  • Often originates from the inner sole of footwear
  • Can cause osteochondritis/osteomyelitis that is difficult to treat
  • Particularly concerning when the puncture is deep and near joints or bones

• Staphylococcus aureus: Second most common pathogen 2

  • Including community-associated MRSA strains which are increasingly common 2, 3

• Beta-hemolytic streptococci: Particularly group B streptococci 2, 3

For Chronic or Previously Treated Wounds

• Polymicrobial infections with 3-5 different organisms 2, 3:
  • Gram-positive aerobes (S. aureus, streptococci, enterococci)
  • Gram-negative aerobes (Enterobacteriaceae)
  • Obligate anaerobes
  • Pseudomonas aeruginosa

Risk Factors for Specific Pathogens

1. Pseudomonas aeruginosa:

   • Puncture through rubber-soled shoes 1, 4, 5
   • Warm, moist environment inside shoes 1
   • Previous antibiotic treatment targeting only gram-positive bacteria 1

2. Antibiotic-resistant organisms:

   • Prior antibiotic exposure 2
   • Previous hospitalization 2
   • Chronic wounds 2, 6
   • Delayed treatment (>48 hours) 5

Clinical Presentation Suggesting Specific Pathogens

Clinical Presentation	Likely Pathogens
Acute cellulitis without open wound	Beta-hemolytic streptococci and S. aureus [2]
Infected puncture wound in antibiotic-naïve patient	S. aureus and beta-hemolytic streptococci [2]
Chronic infected wound or previously treated	S. aureus, beta-hemolytic streptococci, and Enterobacteriaceae [2]
Macerated wound	Pseudomonas aeruginosa (often with other organisms) [2]
Deep puncture through rubber sole with persistent pain	Pseudomonas osteochondritis/osteomyelitis [1,4]

Warning Signs of Pseudomonas Infection

• Persistent pain despite initial antibiotic therapy
• Green-blue discoloration of wound drainage
• Failure to improve on antibiotics targeting only gram-positive bacteria
• Puncture near joints or bones of the foot

Important Caveats

• Delay in seeking treatment significantly worsens outcomes 5
• Foreign body retention (pieces of shoe sole) can complicate treatment and harbor bacteria 5
• Diabetic patients are at particularly high risk for complications 2, 5
• Ultrasonography is useful for detecting retained foreign bodies 5
• Pseudomonas osteochondritis typically requires surgical debridement in addition to antibiotics 4
• Co-infection with S. aureus and P. aeruginosa is more virulent than single pathogen infection 6

Key Points for Management

1. Consider Pseudomonas aeruginosa as a primary pathogen in any puncture wound through a shoe sole
2. Initial empiric antibiotic therapy should cover both S. aureus (including MRSA if prevalent locally) and Pseudomonas aeruginosa
3. Failure to respond to appropriate antibiotics should prompt evaluation for:
   • Retained foreign body
   • Deep tissue infection (abscess, osteomyelitis)
   • Antibiotic-resistant organisms

Remember that successful treatment of Pseudomonas osteochondritis typically requires both surgical debridement and appropriate antibiotic therapy 4.