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Infect. Immun., Jan 1998, 336-342, Vol 66, No. 1
KW Bayles, CA Wesson, LE Liou, LK Fox, GA Bohach and WR Trumble
We examined the invasion of an established bovine mammary epithelial cell
line (MAC-T) by a Staphylococcus aureus mastitis isolate to study the
potential role of intracellular survival in the persistence of
staphylococcal infections. S. aureus cells displayed dose-dependent
invasion of MAC-T cells and intracellular survival. An electron microscopic
examination of infected cells indicated that the bacteria induced
internalization via a mechanism involving membrane pseudopod formation and
then escaped into the cytoplasm following lysis of the endosomal membrane.
Two hours after the internalization of S. aureus, MAC-T cells exhibited
detachment from the matrix, rounding, a mottled cell membrane, and
vacuolization of the cytoplasm, all of which are indicative of cells
undergoing programmed cell death (apoptosis). By 18 h, the majority of the
MAC-T cell population exhibited an apoptotic morphology. Other evidence for
apoptosis was the generation of MAC-T cell DNA fragments differing in size
by increments of approximately 180 bp and terminal deoxynucleotidyl
transferase-mediated dUTP nick end labeling of the fragmented nuclear DNA
of the infected host cells. These results demonstrate that after
internalization S. aureus escapes the endosome and induces apoptosis in
nonprofessional phagocytes.
Copyright © 1998, American Society for Microbiology
Intracellular Staphylococcus aureus escapes the endosome and induces apoptosis in epithelial cells
Department of Microbiology, Molecular Biology and Biochemistry, University of Idaho, Moscow 83844, USA.
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