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Infection and Immunity, July 1999, p. 3339-3347, Vol. 67, No. 7
Department of Microbiology and
Immunology1 and Department of
Ophthalmology,2 Molecular Pathogenesis of
Eye Infections Research Center, Dean A. McGee Eye Institute, University
of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma
Received 29 January 1999/Returned for modification 1 March
1999/Accepted 12 April 1999
Enterococcus faecalis has become a pervasive clinical
problem due to the emergence of resistance to most antibiotics. The cytolysin of E. faecalis is a novel bacterial toxin that
contributes to the severity of disease. It consists of two structural
subunits, which together possess both hemolytic and bactericidal
activity. Both toxin subunits are encoded in a complex operon
frequently harbored on pheromone-responsive plasmids. E. faecalis strains lacking such plasmids are susceptible to the
bactericidal effects of the cytolysin. A novel cytolysin immunity
determinant at the 3' end of the pAD1 cytolysin operon is described in
the present study. Deletion analysis and specific mutagenesis isolated
the immunity function to a single open reading frame. Specific
mutagenesis experiments demonstrate that cytolysin immunity is
unrelated to cytolysin activator (CylA) expression as previously
proposed. Cytolysin immunity is, however, encoded on the same
transcript as and 3' to CylA, and previous associations between
immunity and CylA can be ascribed to the polar behavior of
Tn917 insertion.
0019-9567/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
A Novel Means of Self-Protection, Unrelated to Toxin Activation,
Confers Immunity to the Bactericidal Effects of the
Enterococcus faecalis Cytolysin
*
Corresponding author. Mailing address: Department of
Ophthalmology, University of Oklahoma Health Sciences Center, 608 Stanton L. Young Blvd., Oklahoma City, OK 73104. Phone: (405) 271-1083. Fax: (405) 271-3013. E-mail: mgilmore{at}aardvark.ou.edu.
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