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Growing Staphylococcus aureus in synthetic cystic fibrosis medium promotes colonization in a murine pneumonia model
Justin M Luu1,2, Ian N Moore3, Dina A Moustafa2,4
1Microbiology and Molecular Genetics Program, Graduate Division of Biological and Biomedical Sciences, Laney Graduate School, Emory University, Atlanta, Georgia, USA.
Abstract:
Staphylococcus aureus is a leading cause of bacterial infections worldwide and can lead to diseases, such as osteomyelitis, skin, and lung infections in humans. Murine infection models have been an essential tool to the study of S. aureus virulence, although they do have their limitations. In murine pneumonia models, S. aureus infections are generally not well maintained. We hypothesize that culturing S. aureus under different conditions, such as in Synthetic CF Medium 2 (SCFM2), would increase bacterial respiratory loads compared to growing the bacteria on standard rich medium agar plates. We observed that culturing six S. aureus strains from various sources in SCFM2 resulted in a neutral or increased level of bacterial lung load compared with those cultured on agar plates. Focusing on one strain, WU1, we found that culturing in SCFM2 improved bacterial persistence in the oropharynx and led to a sustained long-term lung infection compared with agar plates. We further noted that mice experienced increased inflammation in both lobes of the lungs when infected with WU1 cultured in SCFM2 compared with agar plates. Overall, we have shown that culturing S. aureus under different conditions prior to infection impacts the level of colonization and host response.
Insights
Culturing Staphylococcus aureus in Synthetic CF Medium 2 (SCFM2) enhances bacterial lung load and persistence in mice. This method improves murine models for studying S. aureus infections and host responses.
Area of Science:
- Microbiology
- Infectious Diseases
- Immunology
Background:
- Staphylococcus aureus is a major global pathogen causing diverse infections.
- Murine models are crucial for studying S. aureus, but maintaining lung infections is challenging.
- Standard culture methods may not fully represent in vivo conditions for S. aureus.
Purpose of the Study:
- To investigate if culturing Staphylococcus aureus in Synthetic CF Medium 2 (SCFM2) improves bacterial load and persistence in murine pneumonia models.
- To assess the impact of SCFM2 pre-culture on host inflammatory responses.
Main Methods:
- Six S. aureus strains were cultured in SCFM2 and on agar plates.
- Bacterial lung loads were compared between culture conditions.
- Persistence in the oropharynx and sustained lung infection were evaluated for strain WU1.
- Lung inflammation was assessed in infected mice.
Main Results:
- SCFM2 culturing resulted in neutral or increased S. aureus lung loads compared to agar.
- SCFM2 pre-culture enhanced WU1 persistence in the oropharynx and led to sustained lung infection.
- Mice infected with SCFM2-cultured WU1 showed increased lung inflammation.
Conclusions:
- Pre-culturing Staphylococcus aureus under specific conditions, like SCFM2, significantly impacts colonization levels and host immune response.
- SCFM2 offers a promising method to improve S. aureus murine infection models for studying virulence and host interactions.
