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Enhanced virulence of Staphylococcus aureus from bovine mastitis induced by growth in milk whey
1Department of Veterinary Microbiology, College of Veterinary Medicine, Swedish University of Agricultural Sciences, Uppsala.
Abstract:
The virulence towards mice of Staphylococcus aureus strains from bovine mastitis was enhanced upon growth in milk whey compared to homologous organisms grown in tryptic soy broth (TSB). In the mouse mastitis model, S. aureus grown in milk whey caused more severe lesions than homologous strains grown in TSB. Staphylococcus aureus strain F1440 grown in milk whey induced 75% mortality and local necrotic reaction in subcutaneously inoculated mice, whereas the homologous strain grown in TSB caused only 5% mortality and slight skin reaction. Extracellular capsule on milk whey-grown, S. aureus could not be demonstrated. However, diffuse type colony morphology could be correlated with an increased virulence of S. aureus towards mice.
Insights
Growing Staphylococcus aureus in milk whey significantly increased its virulence in mice compared to growth in tryptic soy broth. This milk whey-enhanced Staphylococcus aureus caused more severe lesions and higher mortality in a mouse mastitis model.
Area of Science:
- Microbiology
- Veterinary Science
- Pathogen Virulence Studies
Background:
- Bovine mastitis is a significant concern in dairy farming.
- Staphylococcus aureus is a primary causative agent of mastitis.
- Understanding factors that influence S. aureus virulence is crucial for disease control.
Purpose of the Study:
- To investigate the impact of growth medium on the virulence of Staphylococcus aureus from bovine mastitis.
- To compare the pathogenicity of S. aureus grown in milk whey versus tryptic soy broth in a mouse model.
Main Methods:
- Bovine mastitis Staphylococcus aureus strains were cultured in milk whey and tryptic soy broth (TSB).
- Virulence was assessed using a mouse mastitis model with subcutaneous inoculation.
- Lesion severity, mortality rates, and colony morphology were evaluated.
Main Results:
- Staphylococcus aureus grown in milk whey exhibited enhanced virulence towards mice compared to TSB-grown counterparts.
- Milk whey-grown S. aureus caused significantly more severe lesions and higher mortality (75%) than TSB-grown strains (5%).
- Diffuse colony morphology in milk whey-grown S. aureus correlated with increased virulence.
Conclusions:
- Milk whey promotes increased virulence in Staphylococcus aureus relevant to bovine mastitis.
- Growth medium composition significantly affects bacterial pathogenicity.
- Diffuse colony morphology may serve as an indicator of enhanced S. aureus virulence.