Characterization of group B streptococcal invasion in HEp-2 epithelial cells.
The invasion of group B streptococci (GBS) in HEp-2 epithelial cells was analyzed by electron microscopy and a quantitative antibiotic survival assay. Invasion of GBS involved intimate attachment of streptococcal chains, engulfment of the adherent bacteria by cellular protrusions, entry of the bacteria in a 'polar' fashion and formation of membrane-bound vacuoles in which most of the intracellular streptococci resided. At later stages of infection bacteria were also found free in the cytoplasm. Efficient uptake of streptococci by HEp-2 cells occurred within 20 min and live intracellular bacteria were detectable up to 48 h post-infection. Invasion of GBS required activation of the eukaryotic actin microfilament system involving, at least partially, protein kinase signal transduction pathways. Invasion was inhibited in a dose-dependent manner by decreasing extracellular Ca2+ levels as well as by substances known to interfere with eukaryotic calcium regulatory systems. These results suggest that GBS invade HEp-2 cells by triggering calcium-dependent phagocytosis-like internalization mechanisms and persist intracellularly both in vacuoles and free in the cytoplasm.
Valentin-Weigand
P
P
Department of Microbiology, GBF-National Research Centre for Biotechnology, Braunschweig, Germany.
Jungnitz
H
H
Zock
A
A
Rohde
M
M
Chhatwal
G S
GS
D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology; D002103:Cadaverine / Q000031:analogs & derivatives / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D002478:Cells, Cultured / Q000382:microbiology / Q000648:ultrastructure; D003599:Cytoskeleton / Q000187:drug effects / Q000502:physiology; D003609:Dactinomycin / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004848:Epithelium / Q000382:microbiology / Q000648:ultrastructure; D019833:Genistein; D006801:Humans; D007529:Isoflavones / Q000494:pharmacology; D008099:Liver / Q000166:cytology / Q000382:microbiology*; D008854:Microscopy, Electron; D008855:Microscopy, Electron, Scanning; D015739:Nocodazole / Q000494:pharmacology; D015398:Signal Transduction / Q000502:physiology; D019311:Staurosporine / Q000494:pharmacology; D013290:Streptococcal Infections; D013292:Streptococcus agalactiae / Q000187:drug effects / Q000472:pathogenicity* / Q000648:ultrastructure; D014774:Virulence
D000903:Antibiotics, Antineoplastic; D000970:Antineoplastic Agents; D004791:Enzyme Inhibitors; D007529:Isoflavones; D003609:Dactinomycin; D019833:Genistein; D019311:Staurosporine; C008542:monodansylcadaverine; D002103:Cadaverine; D015739:Nocodazole; D002118:Calcium