Bactericidal capacity of newborn phagocytes against group B beta-hemolytic streptococci.

The bactericidal capacity of mononuclear and polymorphonuclear phagocytes obtained from normal newborn infants and from healthy adults was evaluated in vitro, using two group B beta-hemolytic streptococci (GBBHS) serotypes (GBBHS-Ia-SS-615/28 and GBBHS-III-SS-620/50) and uniform opsonic conditions. No intertype differences in bacteriolysis of these two serotypes were observed among leukocytes from newborns or adults. As group, only polymorphonuclear phagocytes from newborns disclosed a significantly lower mean bactericidal capacity than their adult cellular counterpart, and only with respect to GBBHS-III-SS-620/50. On the other hand, 4 or 16 polymorphonuclear samples from newborns tested revealed significantly low bactericidal capacities against both GBBHS serotypes, and an additional sample revealed a bactericidal capacity against GBBHS-III-SS-620/50 alone. Interstrain variations in the intrinsic bactericidal capacity of polymorphonuclear phagocytes from newborns against GBBHS-III may exist, as suggested by a single observation made by using four clinical isolates of GBBHS-III. Such deviant phagocytic capacities of polymorphonuclear phagocytes from newborns may constitute an additional selective risk factor in the genesis of GBBHS sepsis of the newborn.