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Virulence of coagulase-deficient mutants of Staphylococcus aureus in experimental endocarditis
L M Baddour1, M M Tayidi, E Walker
1Department of Medicine, University of Tennessee Medical Center at Knoxville 37920-6999.
Abstract:
A sensitive rat endocarditis model which employed relatively small inocula (< or = 10(4) cfu) was used to examine the role of coagulase in the pathogenesis of infection. Rats with indwelling, intracardiac catheters were challenged intravenously with three strains of Staphylococcus aureus. The virulence of a coagulase-positive parental strain DU5808 was compared in terms of its ID50 for resected vegetations and catheters to that of two coagulase-negative mutant strains (DU5809 and DU5814) which had undergone site-specific mutagenesis. Confidence intervals of infection rates were calculated and comparisons were performed of weights of infected vegetations, bacterial concentrations in vegetations and early mortality rates. From these virulence parameters, it was concluded that there were no differences in virulence among the three strains. The results from this investigation support the previous findings in mouse models of subcutaneous infection and mastitis, which indicated that coagulase production by S. aureus does not appear to function as a virulence factor. Together, these data refute the longheld belief that coagulase is important in the pathogenesis of infection and indicate that other markers of virulence must be operative in diseases caused by the enduring pathogen S. aureus.
Insights
Coagulase, a protein produced by Staphylococcus aureus, does not appear to be a virulence factor in causing infection, according to a rat endocarditis model. This finding challenges the long-held belief about coagulase
Area of Science:
- Microbiology
- Pathogenesis research
- Infectious diseases
Background:
- Coagulase is a protein produced by Staphylococcus aureus.
- Its role in pathogenesis has been historically considered significant.
- Previous studies suggested coagulase is not a key virulence factor.
Purpose of the Study:
- To investigate the role of coagulase in Staphylococcus aureus pathogenesis.
- To compare the virulence of coagulase-positive and coagulase-negative strains.
- To utilize a sensitive rat endocarditis model for infection studies.
Main Methods:
- Employed a rat endocarditis model with intracardiac catheters.
- Challenged rats intravenously with coagulase-positive and negative Staphylococcus aureus strains.
- Assessed virulence through ID50, vegetation weight, bacterial concentration, and mortality rates.
Main Results:
- No significant differences in virulence were observed among the tested strains.
- Coagulase-positive and negative strains exhibited comparable ID50 values.
- Vegetation weights, bacterial loads, and mortality rates were similar across groups.
Conclusions:
- Coagulase production by Staphylococcus aureus does not appear to be a critical virulence factor.
- Findings support previous studies in mouse models.
- Challenges the established belief in coagulase's role in infection pathogenesis.