Among coagulase-negative staphylococci S. epidermidis has been recognized as a frequent cause of severe infections in immunocompromised hosts such as patients with implanted medical devices and newborns nursed in neonatal intensive care units. This phenomenon is usually associated with strains which secret an extracellular highly adhesive material (known as slime) that seems to promote interbacterial shielding and adherence between bacteria and synthetic devices or biological tissues. We have recently shown that the major component of slime material is a 20-kDa sulfated polysaccharide(PS) which represents approximately 60-65% of the slime macromolecules and comprise the major antigenic determinant of slime. Purified rabbit polyclonal PS-specific IgG have shown significant reactivity and specificity only with slime-producing S.epidermidis strains. Furthermore, PS-specific IgG present almost identical in vitro reactivity with human polyvalent immunoglobulin manufactured by Sandoz (Sandoglobulin®, SAGL). In the present study, [SAGL containing ca 99% intact IgG and high reactivity with 20-kDa PS antigen (86-92% reactivity as compared to that of PS-specific IgG), without significant variation within the same lot and lot to lot tested (P≤0.05)] was infused to 14 neonates with a B.W.<1,700 g (0.4 g SAGL/Kg body weight/day) for four consequent days. Sera obtained before infusion (day 0), on the 4th, 8th and 18th day were measured for total IgG by a nephelometric method and PS-specific IgG by indirect ELISA developed in our laboratories. The levels of ca 530±218 mg% for total IgG and 385±160 units/ml for PS-specific IgG on day-0 were increased to ca 1200±96 mg% and 2545±560 units/ml, respectively on day-4. The concentration levels of both total and PS-specific IgG followed similar declining patterns for the time period examined being 850±30 mg% and 1180±492 units/ml on day-8 and 685±95 mg% and 490±185 units/ml on day-18. Considering the 14 neonates examined, only one (ca 7%) developed slime-producing S. epidermidis bacteraemia. Our data indicate that SAGL administration to neonates not only leads to high levels of total IgG that may be protective but also to PS-specific IgG which enhances the humoral response of such susceptible hosts against slime-producing S. epidermidis infections. Due to very low levels of S. epidermidis -specific IgG on day-0, it is suggested that administration of a pre-determined highly reactive human polyvalent immunoglobulin preparation will prevent the majority of neonates against slime-producing S. epidermidis bacteraemia.