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Infect. Immun., 12 1995, 4738-4743, Vol 63, No. 12
P Moreillon, JM Entenza, P Francioli, D McDevitt, TJ Foster, P Francois and P Vaudaux
The pathogenic role of staphylococcal coagulase and clumping factor was
investigated in the rat model of endocarditis. The coagulase-producing and
clumping factor-producing parent strain Staphylococcus aureus Newman and a
series of mutants defective in either coagulase, clumping factor, or both
were tested for their ability (i) to attach in vitro to either rat
fibrinogen or platelet-fibrin clots and (ii) to produce endocarditis in
rats with catheter-induced aortic vegetations. In vitro, the clumping
factor-defective mutants were up to 100 times less able than the wild type
strain to attach to fibrinogen and also significantly less adherent than
the parents to platelet-fibrin clots. Coagulase-defective mutants, in
contrast, were not altered in their in vitro adherence phenotype. The rate
of in vivo infection was inoculum dependent. Clumping factor-defective
mutants produced ca. 50% less endocarditis than the parent organisms when
injected at inoculum sizes infecting, respectively, 40 and 80% (ID40 and
ID80, respectively) of rats with the wild-type strain. This was a trend at
the ID40 but was statistically significant at the ID80 (P < 0.05).
Coagulase-defective bacteria were not affected in their infectivity.
Complementation of a clumping factor-defective mutant with a copy of the
wild-type clumping factor gene restored both its in vitro adherence and its
in vivo infectivity. These results show that clumping factor plays a
specific role in the pathogenesis of S. aureus endocarditis. Nevertheless,
the rate of endocarditis with clumping factor-defective mutants increased
with larger inocula, indicating the contribution of additional pathogenic
determinants in the infective process.
Copyright © 1995, American Society for Microbiology
Role of Staphylococcus aureus coagulase and clumping factor in pathogenesis of experimental endocarditis
Department of Internal Medicine, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland.
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