What is the antimicrobial susceptibility of Dermabacter hominis in a typical adult with a skin or soft‑tissue infection?

Antimicrobial Susceptibility of Dermabacter hominis

Vancomycin, rifampicin, and linezolid are the antibiotics of choice for Dermabacter hominis infections, with 100% susceptibility rates, while penicillins should be avoided due to high resistance rates (84-100%).

Key Susceptibility Patterns

Based on the most recent and comprehensive study 1, D. hominis demonstrates the following susceptibility profile:

Highly Effective Agents (100% susceptibility):

• Vancomycin - remains the drug of choice 1, 2, 3
• Rifampicin - consistently effective 1, 2
• Linezolid - excellent alternative 1, 2

Moderate Susceptibility:

• Ampicillin: 83% susceptible 1 (though older data shows lower rates)
• Ceftriaxone: Only 37% susceptible 1
• Clindamycin: Only 27% susceptible 1

High Resistance (Avoid):

• Benzylpenicillin: 100% resistant 1
• Daptomycin: Intrinsically resistant (MICs 8-48 mg/L) 2
• Erythromycin: 100% resistant 2
• Penicillin: 84% resistant 3

Clinical Implications

Treatment Algorithm:

For confirmed D. hominis skin/soft tissue infection:

1. First-line therapy: Vancomycin IV (15 mg/kg every 12 hours, not exceeding 30 mg/kg/day) 4

   • Alternative: Linezolid 600 mg IV/PO every 12 hours 5

2. Oral step-down options (once clinically stable):

   • Linezolid 600 mg PO every 12 hours 5
   • Consider rifampicin for susceptible isolates

3. Duration: 7-14 days based on clinical response 5, 6

Critical Pitfalls to Avoid:

• Never use daptomycin - D. hominis shows intrinsic high-level resistance despite daptomycin's approval for SSTIs 2
• Avoid empiric penicillins - resistance rates exceed 80% 3
• Don't rely on clindamycin - only 27% susceptibility despite common use for skin infections 1
• Ceftriaxone is unreliable - only 37% susceptible, despite being a common empiric choice 1

Context and Nuances

D. hominis is part of normal skin flora but can cause true infections including bacteremia, bone/joint infections, and peritoneal dialysis-associated peritonitis 1, 2. The organism is frequently isolated in polymicrobial cultures (88% of cases), making clinical significance determination challenging 3.

Important distinction: While guidelines recommend daptomycin for MRSA SSTIs 5, this does NOT apply to D. hominis due to intrinsic resistance. The 2025 study 1 provides the most current resistance data, superseding older patterns from the 1990s 7.

The high vancomycin susceptibility (100%) aligns with broader guideline recommendations for resistant gram-positive organisms in SSTIs 8, 4, making it the most reliable empiric choice when D. hominis is suspected or confirmed.