ADHERENCE OF GROUP-B STREPTOCOCCI TO CULTURED EPITHELIAL-CELLS ROLES OF ENVIRONMENTAL-FACTORS AND BACTERIAL SURFACE COMPONENTS

Group B streptococci (GBS) are the major cause of neonatal pneumonia, sepsis, and meningitis. Steps considered to be important in the pathog enesis of this infection include colonization of the rectum and vagina of the mother, aspiration of GBS into the fetal lung during or just p rior to delivery, and invasion of GBS into pulmonary epithelial cells. We have previously demonstrated that GBS can invade pulmonary epithel ial cells both in vivo and in vitro. Adherence of GBS to epithelial te lls may play an important role in colonization of the rectum and vagin a and constitute a first step in invasion of pulmonary epithelial cell s. Because GBS can both adhere to and invade epithelial cells, we have developed two assays for GBS adherence which measure cell surface and not intracellular bacteria. Using these assays, we were able to demon strate specific adherence of GBS to pulmonary epithelial cells. Adhere nce levels were similar at 4 and 37 degrees C and for log- and station ary-phase bacteria. Physiologic conditions vary considerably between t he rectum, vagina, and lung, and a range of conditions was therefore t ested. Adherence was enhanced in hypotonic solutions, while magnesium and calcium had no effect on adherence at physiologic concentrations. In comparison with adherence at neutral pH, adherence was increased 6- to 20-fold at pH 4, which is the normal vaginal pH. Neither capsular polysaccharide nor lipoteichoic acid was important for adherence in th ese assays. Treatment of GBS with trypsin decreased their adherence by more than 75%, indicating that surface proteins play an important rol e.