PENETRATION OF GROUP-B STREPTOCOCCI THROUGH POLARIZED MADIN-DARBY CANINE KIDNEY-CELLS

Group B streptococci (GBS) are one of the major causes of invasive neo natal infection. The pathogenesis of early onset disease is a multiste p process. Adhesion of GBS to eucaryotic cells is considered to be an important step for the establishment of infection. Subsequent to adhes ion, GBS invade cells and give rise to septicemia and meningitis. To i nvestigate passage of GBS across epithelial cell linings we examined t he interaction be- tween bacteria and Madin-Darby canine kidney (MDCK) cells. When grown on permeable support, these cells form a polarized epithelial monolayer with an apical-to-basolateral orientation, which more reflects the in vivo situation compared with conven- tionally cul tured cells. Our results show that GBS are translo- cated in vacuoles from the apical to the basolateral surface of MDCK cells in a temperat ure-dependent process. The passage of GBS through the cells is selecti ve with only small numbers of bacteria penetrating in the basolateral- to-apical direction. Transcytosis of GBS starts before decrease in tra nsepithelial resistance of the monolayer. These data suggest a mechani sm for traversal of GBS over intact chorioamniotic membranes and from alveoli into the circulation of the fetus.