Valentin-Weigand P, Jungnitz H, Zock A, Rohde M, Chhatwal G S
Department of Microbiology, GBF-National Research Centre for Biotechnology, Braunschweig, Germany.
FEMS Microbiol Lett. 1997 Feb 1;147(1):69-74. doi: 10.1111/j.1574-6968.1997.tb10222.x.
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.
