What does it mean to have scant squamous epithelial cells, moderate Gram-positive cocci, and few Gram-positive bacilli - coryneform on a wound culture of a skin wound?

Interpretation of Wound Culture Results

This culture result indicates likely superficial contamination rather than true infection, with the scant squamous epithelial cells suggesting inadequate specimen collection from the wound surface rather than deep tissue. 1, 2

Understanding the Culture Components

Squamous Epithelial Cells (Scant)

• Presence of squamous epithelial cells indicates surface contamination and suggests the specimen was obtained by swabbing the wound surface rather than from deep tissue 1
• This finding significantly reduces the reliability of the culture results, as it indicates the sample likely captured colonizing organisms rather than true pathogens 1
• Guidelines specifically recommend avoiding swab specimens because they provide less accurate results and commonly pick up superficial contaminants 1

Gram-Positive Cocci (Moderate)

• These likely represent Staphylococcus species or Streptococcus species, which are the most common pathogens in acute wound infections 1
• In mild infections without recent antibiotic exposure, these organisms are predictably the sole pathogens and are clinically significant 1
• However, given the presence of squamous cells, these may represent skin colonizers rather than true pathogens 1

Gram-Positive Bacilli - Coryneform (Few)

• Corynebacterium species and other coryneform bacteria are typically skin colonizers and should generally NOT be targeted with antibiotic therapy 1
• The IWGDF/IDSA 2023 guidelines explicitly state that "targeting antibiotic treatment against likely colonizers (e.g., coagulase-negative staphylococci and corynebacteria) may be unnecessary" 1
• These organisms can occasionally be true pathogens, but only when they grow repeatedly from reliable specimens (not surface swabs) or from deep tissue cultures 1
• The presence of coryneforms in this context, combined with squamous cells, strongly suggests contamination 3, 4

Clinical Decision-Making Algorithm

Step 1: Assess Clinical Signs of Infection

• Base treatment decisions on clinical presentation, not culture results alone 1, 2
• Look for: purulence, erythema, warmth, tenderness, induration, or systemic signs 1
• If the wound shows no clinical signs of infection, do not treat based on culture results 1

Step 2: Evaluate Specimen Quality

• This specimen is of poor quality due to the presence of squamous epithelial cells 1
• If clinical infection is present, repeat the culture using proper technique: cleanse and debride the wound first, then obtain tissue by curettage or biopsy from the wound base 1
• Avoid swab specimens, especially from inadequately debrided wounds 1

Step 3: Determine Need for Antibiotic Therapy

• If the wound is clinically uninfected, do not prescribe antibiotics regardless of culture results 1
• If clinically infected and this is a mild infection without recent antibiotic exposure, empiric therapy targeting Gram-positive cocci (Staphylococcus and Streptococcus) is appropriate 1
• Do not target the coryneform bacteria unless they grow repeatedly from properly obtained deep tissue specimens 1

Common Pitfalls to Avoid

• Do not treat colonization: The presence of bacteria in a wound does not mean it requires antibiotics 1
• Do not rely on surface swab cultures: These commonly yield misleading results with multiple colonizing organisms 1, 2
• Do not target all organisms cultured: In polymicrobial cultures from poor specimens, focus only on likely pathogens (Staphylococcus, Streptococcus) and ignore likely colonizers (Corynebacterium, coagulase-negative staphylococci) 1
• Avoid requesting laboratories to "report everything that grows": This leads to treatment of colonizing organisms rather than true pathogens 2

When to Repeat the Culture

If clinical infection is present, this culture should be repeated with proper technique 1, 2:

• Cleanse and debride the wound thoroughly first 1, 2
• Obtain tissue by curettage (scraping with sterile scalpel) or biopsy from the wound base 1
• Send for both aerobic and anaerobic culture with Gram stain 1
• Collect before initiating antibiotic therapy if possible 1