Related Experiment Videos
Murine model of cutaneous infection with gram-positive cocci
1Department of Medicine, Vanderbilt University Medical School, Nashville, Tennessee 37232.
Abstract:
Staphylococcus aureus has remained an important cause of nosocomial wound infections, but standardized or reproducible systems for analyzing cutaneous infections caused by S. aureus do not exist. A variety of foreign materials, variable inocula, and skin traumas have been used to promote infection. To minimize these variables and ensure reproducibility, we chose a model using subcutaneous injections of a fixed quantity of dextran microbeads (Cytodex) as the foreign material added to standardized broth suspensions of S. aureus. Suspensions (0.2 ml) injected into an outbred strain of immunocompetent hairless mice generated reproducible, measurable lesions. With S. aureus Smith Diffuse, fluctuant, erythematous lesions with a peak diameter of 15 mm were observed; these lesions yielded purulent material containing gram-positive cocci and neutrophils and yielded growth of S. aureus on culture. Lesion size was proportional to the bacterial inoculum size. Histologic examination of excised lesions revealed typical abscesses. A second strain of S. aureus (SLC3) produced dermonecrosis instead of abscesses at an inoculum size of 10(7) CFU. Control injections with a sterile Cytodex suspension regularly produced nondraining, nonerythematous nodules with maximum diameters of less than or equal to 5 mm. Streptococcus pyogenes produced late-onset necrotic lesions and abscesses. Using a foreign substance, this model generates easily observed and reproducible cutaneous infection with S. aureus and streptococci that can potentially discriminate between inter- and intrastrain differences. Such a model could be used to test the pathogenicity of isogeneic strains of these bacterial species and to evaluate the efficacy of antimicrobial agents.
Insights
Researchers developed a reproducible mouse model for studying Staphylococcus aureus skin infections. This model uses microbeads and standardized bacterial injections to create measurable lesions, aiding in pathogenicity and antimicrobial agent testing.
Area of Science:
- Microbiology
- Infectious Diseases
- Dermatology
Background:
- Staphylococcus aureus is a major cause of hospital-acquired wound infections.
- Existing models for studying S. aureus skin infections lack standardization and reproducibility.
- Variability in foreign materials, bacterial doses, and skin trauma complicates infection analysis.
Purpose of the Study:
- To develop a standardized and reproducible model for analyzing cutaneous infections caused by Staphylococcus aureus.
- To minimize variables in infection models by using a fixed quantity of foreign material and standardized bacterial suspensions.
- To create a model for testing bacterial pathogenicity and evaluating antimicrobial agents.
Main Methods:
- Subcutaneous injection of standardized broth suspensions of S. aureus with dextran microbeads (Cytodex) into hairless mice.
- Utilizing a fixed quantity of microbeads as foreign material to ensure reproducibility.
- Monitoring lesion development, size, and characteristics, including purulence, erythema, and histology.
Main Results:
- Reproducible, measurable lesions were generated in mice following S. aureus injections.
- S. aureus Smith Diffuse produced fluctuant, erythematous lesions with abscesses, proportional to inoculum size.
- A second strain, S. aureus SLC3, induced dermonecrosis, while control injections produced non-inflammatory nodules.
Conclusions:
- The developed model provides a reproducible method for generating and analyzing S. aureus cutaneous infections.
- This model can be used to differentiate between bacterial strains and assess pathogenicity.
- The model holds potential for evaluating the efficacy of antimicrobial agents against S. aureus and streptococci.