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Infect Immun, February 1998, p. 448-450, Vol. 66, No. 2
Department of Infectious
Diseases1 and
Hemostasis Thrombosis
Research Centre,2 Leiden State University
Hospital, Leiden, The Netherlands
Received 28 July 1997/Returned for modification 9 September
1997/Accepted 14 November 1997
The endocardial vegetation which is formed in the course of
bacterial endocarditis (BE) contains tissue factor (TF)-dependent procoagulant activity. Earlier studies showed that monocytes are the
main source of TF in the vegetations. The TF activity (TFA) of
vegetations isolated from Streptococcus sanguis-infected
rabbits depended on the numbers of bacteria as well as monocytes in the vegetation. In this study, we investigated whether for
Staphylococcus epidermidis, a frequent pathogen in BE, an
effect similar to that found for S. sanguis could be shown.
In vitro, S. epidermidis was found to stimulate TFA of
fibrin adherent monocytes significantly. This stimulation was maximal
at a bacterium-to-monocyte ratio of 7. In vivo, TFA was found to be
significantly higher in S. epidermidis-infected than in
sterile catheter-induced vegetations. Reduction of vegetational
bacterial numbers by teicoplanin treatment lead to a small but
significant decrease of TFA. Reduction of monocyte numbers by etoposide
did not affect vegetational TFA. Comparison of data for S. epidermidis and S. sanguis revealed that at
equivalent bacterial numbers, vegetational TFAs were approximately the
same for both microorganisms. Combining the results of the present
study with those of a previous study using S. sanguis, we
conclude that the main factor determining monocyte-dependent vegetational TFA is the number of vegetation-associated bacteria. The
lower TFA found for S. epidermidis-infected than for
S. sanguis-infected vegetations can be explained by the
significantly lower bacterial numbers in the infected vegetations and
consequently a lower stimulation of vegetation-associated monocytes.
0019-9567/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Role of Monocytes and Bacteria in
Staphylococcus epidermidis Endocarditis
*
Corresponding author. Mailing address: Leiden
University Hospital, Department of Infectious Diseases, C-5-P, P.O. Box
9600, 2300 RC Leiden, The Netherlands. Phone: 31-71-5262620. Fax:
31-71-5266758. E-mail: J.Thompson{at}Thuisnet.LeidenUniv.nl.
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