Related Experiment Video
Updated: Jun 16, 2026
A Mouse Model to Assess Innate Immune Response to Staphylococcus aureus Infection
Published on: February 28, 2019
Clearance of experimental cutaneous Staphylococcus aureus infections in mice
Charles C Onunkwo1, Beth L Hahn, Peter G Sohnle
1Division of Infectious Diseases, Department of Medicine, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
Abstract:
Staphylococcal skin infections are quite common in human patients. These infections often clear spontaneously, but may also progress locally and/or disseminate to cause serious and sometimes fatal deep infections. The present studies were undertaken to examine the clearance phase of experimental cutaneous Staphylococcus aureus infections in a mouse model system. Previous work in this system has shown that staphylococci applied to the skin rapidly disseminate to the spleen and kidney. In the present experiments the bacteria were found to persist at the skin infection site at a time (8 days after inoculation) when they had disappeared from the spleen and kidney. Examination of the infected skin at earlier times revealed rapid (within 6 h) invasion into the stratum corneum, stratum Malpighii, and dermis, but subsequent redistribution of bacteria (at 1-2 days) to more superficial sites, particularly crusts located just above the skin surface. The crusts seen in these infections were of two distinct types, which were termed type 1 and type 2. Type 1 crusts appeared first, consisted of bacteria, inflammatory cells, and debris, and developed over an intact epidermis. Type 2 crusts arose from the process of dermal necrosis previously reported to take place at 2 days in this model system. In the latter situation the bacteria were not really cleared from the epidermis and dermis; rather those layers were transformed into a superficial crust that contained the bacteria. Deep hair follicle infections in the dermis were found in these infections, but they did not persist and did not seem to be a reservoir for organisms in the dermis. Resolution of these experimental infections appeared to involve redistribution of invading bacteria to more superficial locations in crusts above the skin surface, marked proliferation of the epidermis, loss of the bacteria-laden crusts from the skin, and eventual healing of the cutaneous damage.
Insights
Staphylococcus aureus skin infections in mice show bacteria persisting in superficial crusts, not deep tissues. Clearance involves bacterial redistribution to crusts and epidermal healing.
Area of Science:
- Microbiology
- Dermatology
- Immunology
Background:
- Staphylococcal skin infections are common and can lead to severe, disseminated disease.
- Previous studies show Staphylococcus aureus rapidly disseminates from skin to spleen and kidney.
- The clearance phase of cutaneous Staphylococcus aureus infections requires further investigation.
Purpose of the Study:
- To investigate the clearance mechanisms of experimental Staphylococcus aureus skin infections in a mouse model.
- To determine the location and persistence of Staphylococcus aureus during the resolution of skin infections.
- To characterize the types of crusts formed during cutaneous staphylococcal infections.
Main Methods:
- Experimental cutaneous Staphylococcus aureus infection in a mouse model.
- Bacterial load assessment in skin, spleen, and kidney at various time points post-inoculation.
- Histological examination of infected skin to identify bacterial location and tissue response.
- Classification and characterization of crust types formed during infection.
Main Results:
- Staphylococcus aureus persisted in skin infection sites for at least 8 days, while clearing from spleen and kidney.
- Bacteria rapidly invaded skin layers within 6 hours, then redistributed to superficial crusts by 1-2 days.
- Two distinct crust types (Type 1 and Type 2) were identified, with Type 2 associated with dermal necrosis.
- Deep hair follicle infections were observed but did not persist or act as a bacterial reservoir.
- Resolution involved bacterial redistribution to crusts, epidermal proliferation, crust shedding, and healing.
Conclusions:
- Cutaneous Staphylococcus aureus infections in mice resolve through bacterial relocation to superficial crusts rather than elimination from deeper skin layers.
- Epidermal proliferation and shedding of bacteria-laden crusts are key events in the resolution of these experimental skin infections.
- The mouse model effectively mimics aspects of staphylococcal skin infection clearance, highlighting the role of superficial structures in resolution.
Related Concept Videos
01:29Staphylococcal Skin Infections
01:25Clinical Significance of Antibiotic Resistance