Related Experiment Video
Updated: Aug 18, 2026
Subcutaneous Infection of Methicillin Resistant Staphylococcus Aureus (MRSA)
Published on: February 9, 2011
Staphylococcus aureus infection on cut wounds in the mouse skin: experimental staphylococcal botryomycosis
Abstract:
Staphylococcus aureus cells were inoculated on the cut wounds in the skin of cyclophosphamide-treated mice. Biopsy specimens were taken from three mice at 1, 3, 6, 12, 24, 36, 48 and 60 h after the inoculation and were examined by light and electron microscopies. One hour after the inoculation Staphylococcus aureus cells were seen around the cut wound and deeper into the subcutaneous tissue. By 6 h after the inoculation, Staphylococcus aureus cells formed clusters of bacterial colonies. By 36 h after the inoculation inflammatory cells, mainly polymorphonuclear leukocytes and macrophages, were seen around the clusters. Electron microscopic examination revealed fibril-like structures around the Staphylococcus aureus cells at 1 h. The Staphylococcus aureus cells were enclosed in membrane-like structures at 3 h. The membrane-like structures and the fibril-like structures were positive for Ruthenium red. By 12 h after the inoculation, the membrane-like structures increased in thickness and in electron density. Inflammatory cells were seen around but outside of the membrane-like structures at 24, 36 and 48 h. At 60 h the tissues around the membrane-like structures were degenerated and almost necrotic. These results suggest that Staphylococcus aureus cells may form biofilm in dermal or subcutaneous tissues in a neutropenic condition.
Insights
Staphylococcus aureus can form biofilms in skin wounds of immunosuppressed mice. These bacterial structures, encased in protective layers, trigger inflammation and tissue damage over time.
Area of Science:
- Microbiology
- Immunology
- Dermatology
Background:
- Staphylococcus aureus is a common pathogen causing skin infections.
- Neutropenia, a condition of low white blood cell count, increases susceptibility to infections.
- Biofilm formation by bacteria contributes to persistent and difficult-to-treat infections.
Purpose of the Study:
- To investigate the in vivo behavior of Staphylococcus aureus in a neutropenic mouse wound model.
- To characterize the early stages of bacterial colonization and host response.
- To determine if Staphylococcus aureus forms biofilm-like structures in dermal and subcutaneous tissues.
Main Methods:
- Cutaneous wounds were created on cyclophosphamide-treated (neutropenic) mice.
- Staphylococcus aureus was inoculated onto the wounds.
- Biopsy specimens were collected at various time points (1-60 hours post-inoculation).
- Light and electron microscopy were used for examination.
- Ruthenium red staining was employed to detect extracellular matrix components.
Main Results:
- Staphylococcus aureus colonized wounds and subcutaneous tissue within 1 hour.
- Bacterial clusters formed by 6 hours.
- Fibril-like and membrane-like structures surrounding bacteria were observed by 1 and 3 hours, respectively.
- These structures stained positive with Ruthenium red, indicating extracellular matrix.
- Inflammatory cells infiltrated by 36 hours.
- Tissue degeneration and necrosis were evident by 60 hours.
Conclusions:
- Staphylococcus aureus can form biofilm-like structures in vivo in a neutropenic host.
- These structures appear to protect bacteria from host immune cells.
- The findings suggest a potential mechanism for persistent S. aureus wound infections in immunocompromised individuals.
Related Concept Videos
01:23Skin Diseases and Disorders
Gram-positive Staphylococcus spp. and Streptococcus spp. are responsible for many of the most common skin infections. However, many...
01:29Staphylococcal Skin Infections