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Updated: Apr 12, 2026
Author Spotlight: Studying Host-Microbe Interactions in Wound Biofilm Formation
Published on: June 16, 2023
New insights in Staphylococcus pseudintermedius pathogenicity: antibiotic-resistant biofilm formation by a human
Arianna Pompilio1,2, Serena De Nicola3,4, Valentina Crocetta5,6
1Department of Medical, Oral, and Biotechnological Sciences, "G. d'Annunzio" University, Via Vestini 31, Chieti, 66100, Italy. ariannapompilio@yahoo.it.
Background:
Staphylococcus pseudintermedius is an opportunistic pathogen recognized as the leading cause of skin, ear, and post-operative bacterial infections in dogs and cats. Zoonotic infections have also recently been reported causing endocarditis, infection of surgical wounds, rhinosinusitis, and catheter-related bacteremia. The aim of the present study is to evaluate, for the first time, the pathogenic potential of S. pseudintermedius isolated from a human infection. To this end, strain DSM 25713, which was recently isolated from a wound of a leukemic patient who underwent a bone marrow transplantation, was investigated for biofilm formation and antibiotic-resistance under conditions relevant for wound infection.
Results:
The effect of pH (5.5, 7.1, and 8.7) and the presence of serum (diluted at 1:2, 1:10, and 1:100) on biofilm formation was assessed through a crystal violet assay. The presence of serum significantly reduced the ability to form biofilm, regardless of the pH value tested. In vitro activity of eight antibiotics against biofilm formation and mature 48 h-old biofilms was comparatively assessed by crystal violet assay and viable cell count, respectively. Antibiotics at sub-inhibitory concentrations reduced biofilm formation in a dose-dependent manner, although cefoxitin was the most active, causing a significant reduction already at 1/8xMIC. Rifampicin showed the highest activity against preformed biofilms (MBEC90: 2xMIC). None of the antibiotics completely eradicated the preformed biofilms, regardless of tested concentrations. Confocal and electron microscopy analyses of mature biofilm revealed a complex "mushroom-like" architecture consisting of microcolonies embedded in a fibrillar extracellular matrix.
Conclusions:
For the first time, our results show that human wound-associated S. pseudintermedius is able to form inherently antibiotic-resistant biofilms, suggestive of its pathogenic potential, and consistent with recent reports of zoonotic infections.
Insights
Staphylococcus pseudintermedius, a common pet pathogen, can form antibiotic-resistant biofilms in human wound infections. This study shows its pathogenic potential in humans, highlighting the need for further research into zoonotic risks.
Area of Science:
- Microbiology
- Infectious Diseases
- Veterinary Medicine
Background:
- Staphylococcus pseudintermedius is a major cause of bacterial infections in companion animals.
- Zoonotic transmission of S. pseudintermedius to humans has been increasingly reported.
- This study investigates the pathogenic potential of a human-isolated S. pseudintermedius strain.
Purpose of the Study:
- To evaluate the biofilm formation capacity of S. pseudintermedius from a human wound infection.
- To assess the antibiotic resistance of S. pseudintermedius biofilms.
- To understand the role of environmental factors (pH, serum) on biofilm development.
Main Methods:
- Crystal violet assay to quantify biofilm formation.
- In vitro antibiotic susceptibility testing against planktonic and biofilm forms.
- Confocal and electron microscopy to analyze biofilm architecture.
- Evaluation of pH and serum effects on biofilm development.
Main Results:
- Serum presence significantly inhibited biofilm formation across tested pH levels.
- Sub-inhibitory antibiotic concentrations reduced biofilm formation in a dose-dependent manner.
- Rifampicin demonstrated the highest activity against preformed biofilms; no antibiotic eradicated biofilms.
- Complex "mushroom-like" biofilm architecture with extracellular matrix was observed.
Conclusions:
- Human wound-associated S. pseudintermedius exhibits inherent antibiotic resistance in biofilms.
- The findings support the pathogenic potential of this bacterium in human infections.
- Results align with increasing reports of S. pseudintermedius zoonotic infections.
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