IAI FigSearch
Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Giguère, S.
Right arrow Articles by Prescott, J. F.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Giguère, S.
Right arrow Articles by Prescott, J. F.

 Previous Article  |  Next Article 

Infection and Immunity, July 1999, p. 3548-3557, Vol. 67, No. 7
0019-9567/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.

Role of the 85-Kilobase Plasmid and Plasmid-Encoded Virulence-Associated Protein A in Intracellular Survival and Virulence of Rhodococcus equi

Steeve Giguère,1 Mary K. Hondalus,2 Julie A. Yager,1 Patricia Darrah,3 David M. Mosser,3 and John F. Prescott1,*

Department of Pathobiology, University of Guelph, Guelph, Ontario N1G 2W1, Canada1; Howard Hughes Medical Research Institute, Albert Einstein College of Medicine, Bronx, New York 104612; and Department of Microbiology and Immunology, Temple University School of Medicine, Philadelphia, Pennsylvania 191403

Received 28 January 1999/Returned for modification 25 February 1999/Accepted 5 April 1999

Rhodococcus equi is a facultative intracellular pathogen of macrophages and a cause of pneumonia in young horses (foals) and immunocompromised people. Isolates of R. equi from pneumonic foals typically contain large, 85- or 90-kb plasmids encoding a highly immunogenic virulence-associated protein (VapA). The objective of this study was to determine the role of the 85-kb plasmid and VapA in the intracellular survival and virulence of R. equi. Clinical isolates containing the plasmid and expressing VapA efficiently replicated within mouse macrophages in vitro, while plasmid-cured derivatives of these organisms did not multiply intracellularly. An isolate harboring the large plasmid also replicated in the tissues of experimentally infected mice, whereas its plasmid-cured derivative was rapidly cleared. All foals experimentally infected with a plasmid-containing clinical isolate developed severe bronchopneumonia, whereas the foals infected with its plasmid-cured derivative remained asymptomatic and free of visible lung lesions. By day 14 postinfection, lung bacterial burdens had increased considerably in foals challenged with the plasmid-containing clinical isolate. In contrast, bacteria could no longer be cultured from the lungs of foals challenged with the isogenic plasmid-cured derivative. A recombinant, plasmid-cured derivative expressing wild-type levels of VapA failed to replicate in macrophages and remained avirulent for both mice and foals. These results show that the 85-kb plasmid of R. equi is essential for intracellular replication within macrophages and for development of disease in the native host, the foal. However, expression of VapA alone is not sufficient to restore the virulence phenotype.

* Corresponding author. Mailing address: Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, Ontario N1G 2W1, Canada. Phone: (519) 824-4120, ext. 4716. Fax: (519) 767-0809. E-mail: jprescott{at}ovcnet.uoguelph.ca.

Infection and Immunity, July 1999, p. 3548-3557, Vol. 67, No. 7
0019-9567/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.


This article has been cited by other articles:



Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
J. Bacteriol. J. Virol. Eukaryot. Cell
Microbiol. Mol. Biol. Rev. Clin. Vaccine Immunol. All ASM Journals

Copyright © 1999 by the American Society for Microbiology. All rights reserved.