EXPERIMENTAL NEONATAL GROUP-B STREPTOCOCCAL PNEUMONIA - EFFECT OF A MODIFIED PORCINE SURFACTANT ON BACTERIAL PROLIFERATION IN VENTILATED NEAR-TERM RABBITS

We studied bacterial proliferation in relation to surfactant treatment in a model of neonatal group B streptococcal (GBS) pneumonia. Surfact ant (Curosurf) was isolated from pig lungs with a method preserving on ly polar lipids and hydrophobic proteins. Near-term rabbit fetuses wer e ventilated in a body plethysmograph system. At 15 min, a suspension of GBS strain 090 Ia LD (5 mL/kg, concentration similar to 10(9)/mL) w as instilled intratracheally. At 30 min, surfactant (n = 12) or steril e saline (n = 13) was administered via the airways (2.5 mL/kg). A cont rol group (n = 12) received the same volumes of saline. After 5 h the animals were killed, and samples for blood cultures and blood gases we re taken from the heart. The left lung was aseptically removed, weighe d, homogenized, serially diluted, and cultured on blood agar plates. T he results were expressed as mean log(10) colony forming units/g lung +/- SD. Compared with animals (n = 12) killed immediately after GBS in stillation (8.13 +/- 0.54), there was a significant increase in bacter ial numbers in bath groups ventilated for 5 h, but values for surfacta nt-treated animals (8.96 +/- 0.38) were lower than those for animals r eceiving saline (9.46 +/- 0.50; p < 0.05). After 5 h, 96% of GBS-infec ted animals had positive blood cultures. Light microscopic examination of the right lung of GBS-infected animals revealed inflammatory chang es that tended to be less prominent in surfactant-treated rabbits. We conclude that intratracheal inoculation of near-term rabbits with GBS resulted in a significant bacterial proliferation during 5 h of ventil ation and that bacterial growth was mitigated by treatment with surfac tant.