Combined treatment with surfactant and specific immunoglobulin reduces bacterial proliferation in experimental neonatal group B streptococcal pneumonia

Neonates suffering from group B streptococcal (GBS) pneumonia often lack ty pe-specific opsonizing antibodies. We studied the influence of combined int ratracheal treatment with surfactant and a specific antibacterial polyclona l antibody (IgG fraction) on bacterial proliferation and lung function in a n animal model of CBS pneumonia. Near-term newborn rabbits received an intr atracheal injection of either the specific IgG antibody, nonspecific IgG, s urfactant, a mixture of surfactant and the antibody, or 0.9% saline. At 30 min the rabbits were infected with a standard dose (10(8)) Of the encapsula ted CBS strain 090 la. After 5 h of mechanical ventilation the mean estimat ed Increase in bacterial number in lung homogenate (log(10) colonies/g) was 0.76 in the antibody group, 0.92 in the nonspecific IgG group, 0.55 in the surfactant group, and 1.29 in the saline group. A mean decrease in bacteri al number (-0.05) was observed in the group that received combined treatmen t with surfactant and antibody (p < 0.05 versus all other groups). Lung-tho rax compliance was significantly higher in both groups of surfactant-treate d animals compared with saline or IgG treatment. We conclude that in experi mental neonatal CBS pneumonia combined treatment with surfactant and a spec ific immunoglobulin against GBS reduced bacterial proliferation more effect ively than either treatment alone.