Adaptation of Staphylococcus aureus in a Medium Mimicking a Diabetic Foot Environment
Cassandra Pouget1, Claude-Alexandre Gustave2, Christelle Ngba-Essebe1
1Virulence Bactérienne et Infections Chroniques, INSERM U1047, Université de Montpellier, 30908 Nîmes, France.
Abstract:
Staphylococcus aureus is the most prevalent pathogen isolated from diabetic foot infections (DFIs). The purpose of this study was to evaluate its behavior in an in vitro model mimicking the conditions encountered in DFI. Four clinical S. aureus strains were cultivated for 16 weeks in a specific environment based on the wound-like medium biofilm model. The adaptation of isolates was evaluated as follows: by Caenorhabditis elegans model (to evaluate virulence); by quantitative Reverse Transcription-Polymerase Chain Reaction (qRT-PCR) (to evaluate expression of the main virulence genes); and by Biofilm Ring test® (to assess the biofilm formation). After 16 weeks, the four S. aureus had adapted their metabolism, with the development of small colony variants and the loss of β-hemolysin expression. The in vivo nematode model suggested a decrease of virulence, confirmed by qRT-PCRs, showing a significant decrease of expression of the main staphylococcal virulence genes tested, notably the toxin-encoding genes. An increased expression of genes involved in adhesion and biofilm was noted. Our data based on an in vitro model confirm the impact of environment on the adaptation switch of S. aureus to prolonged stress environmental conditions. These results contribute to explore and characterize the virulence of S. aureus in chronic wounds.
Insights
Staphylococcus aureus adapts to chronic wound conditions by altering its metabolism and reducing virulence. This study shows how prolonged stress impacts bacterial behavior, affecting virulence gene expression and biofilm formation.
Area of Science:
- Microbiology
- Infectious Diseases
- Wound Healing
Background:
- Staphylococcus aureus is a common cause of diabetic foot infections (DFIs).
- Understanding bacterial adaptation in chronic wounds is crucial for effective treatment.
- DFIs present a unique, prolonged stress environment for pathogens.
Purpose of the Study:
- To investigate the adaptation of Staphylococcus aureus in an in vitro model simulating DFI conditions.
- To evaluate changes in virulence and biofilm formation over time.
- To analyze the expression of key virulence genes under prolonged stress.
Main Methods:
- Cultivation of four clinical S. aureus strains in a wound-like biofilm model for 16 weeks.
- Assessment of virulence using a Caenorhabditis elegans model.
- Gene expression analysis via quantitative Reverse Transcription-Polymerase Chain Reaction (qRT-PCR).
- Biofilm formation evaluation using the Biofilm Ring test®.
Main Results:
- S. aureus developed small colony variants and lost beta-hemolysin expression after 16 weeks.
- Virulence decreased, as indicated by the C. elegans model and reduced expression of toxin-encoding genes.
- Expression of adhesion and biofilm-related genes significantly increased.
- Metabolic adaptation occurred in response to the prolonged stress environment.
Conclusions:
- The in vitro model effectively demonstrates S. aureus adaptation to chronic wound conditions.
- Environmental factors significantly influence S. aureus virulence and behavior.
- These findings enhance our understanding of S. aureus virulence in chronic wounds.
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