Experimental Neonatal Group B Streptococcal Pneumonia: Effect of a Modified Porcine Surfactant on Bacterial Proliferation in Ventilated Near-Term Rabbits

Abstract

jWe studied bacterial proliferation in relation to surfac-bacterial numbers in both groups ventilated for 5 h, but tant treatment in a model of neonatal group B streptococcal values for surfactant-treated animals (8.96 + 0.38) were (GBS) pneumonia. Surfactant (Curosurf) was isolated from lower than those for animals receiving saline (9.46 + 0.50; pig lungs with a method preserving only polar lipids and p < 0.05). After 5 h, 96% of GBS-infected animals had hydrophobic proteins. Near-term rabbit fetuses were ven-positive blood cultures. Light microscopic examination of tilated in a body plethysmograph system. At 15 min, a the right lung of GBS-infected animals revealed inflammasuspension of GBS strain 090 Ia LD (5 mL/kg, concentra-tory changes that tended to be less prominent in surfactanttion -109/mL) was instilled intratracheally. At 30 min, treated rabbits. We conclude that intratracheal inoculation surfactant (n = 12) or sterile saline (n = 13) was adminis-of near-term rabbits with GBS resulted in a significant tered via the airways (2.5 mL/kg). A control group (n = 12) bacterial proliferation during 5 h of ventilation and that received the same volumes of saline. After 5 h the animals bacterial growth was mitigated by treatment with surfacwere killed, and samples for blood cultures and blood gases tant. (Pediatr Res 36: [784][785][786][787][788][789][790][791] 1994) were taken from the heart. The left lung was aseptically removed, weighed, homogenized, serially diluted, and cultured on blood agar plates. The results were expressed as Abbreviations mean log,, colony forming units/g lung + SD. Compared CFU, colony forming unit with animals (n = 12) killed immediately after GBS instil-GBS, group B streptococcus lation (8.13 2 0.54), there was a significant increase in RDS, respiratory distress syndrome GBS is a frequently encountered pathogen in the neonatal period (1). Vaginal colonization with GBS is commonly found in pregnant women. Vertical transmission occurs in approximately 40% of deliveries, but only approximately 1% of neonates born to these mothers develop clinical signs of GBS infection (2). If diagnosis and treatment are delayed, the condition has a substantial mortality, especially in premature infants (2). Susceptibility to GBS infections depends on host defense factors (e-g. lack of type-specific opsonizing antibodies) and Received January 26, 1994; accepted June 21, 1994. virulence factors (e-g. polysaccharide capsule) of the infecting microorganism (3-6).Animal models using rabbits, mice, and rats have been used for studies of experimental neonatal GBS infections (7)(8)(9). In these studies, the animals were either infected b y injection (7, 9) o r a bacterial suspension was nebulized via the airways in spontaneously breathing animals (8,9). Our intention was t o develop a model of GBS pneumonia in ventilated newborn rabbits infected b y intratracheal injection of a bacterial suspension.RDS and GBS pneumonia are difficult to differentiate o n clinical grounds (lo), and therefore neonates with ...

Influence of Partial Liquid Ventilation on Bacterial Growth and Alveolar Expansion in Newborn Rabbits with Group B-Streptococcal Pneumonia

“…Bacterial proliferation follows a logarithmic growth curve, therefore results are presented as log 10 CFU/g BW. Previous investigations revealed a close correlation between the amount of bacteria administered intratracheally and the number of CFU present in lung homogenates from animals killed 1 min after the GBS suspension was instilled in the airways (17). Consequently, such controls were not included in the present study.…”

“…Peak inspiratory pressure was recorded and adjusted for each animal to provide a tidal volume of 8 -10 mL/kg (18). No positive end-expiratory pressure was applied, to unmask differences in alveolar stability related to abnormalities of the surfactant system (17). After a stabilization period of 30 min, the animals were randomly assigned to PLV or continued CMV.…”

“…A suspension of GBS was prepared as previously described (17). In short, an encapsulated low-density phase variant of GBS was processed from the reference strain 090 Ia Colindale by repeated gradient centrifugation.…”

The Pulmonary Surfactant System: Biochemical and Clinical Aspects

“…The growth of group B streptococs, intratracheally inoculated, was mitigated by treatment with surfactant devoid of SP-A [124,285], indicating that other surfactant components also have bactericidal activity. The presence of SP-A potentiates the antibacterial functions of alveolar macrophages [177] by modulating the immune cell function in the lung by regulating the cytokine production and immunoglobulin secretion [176].…”

The influence of porcine cathelicidins on neutrophils isolated from rabbits in the course of bone graft implantation

“…Curosurf as a modified natural surfactant isolated from minced porcine lungs consisted of phospholipids, prophenin, PF-18 and surfactant proteins SP-B and SP-C (Wang et al, 2004). This cathelicidin-containing mixture was also used in treatment of experimentally induced bacterial pneumonia in neonate rabbits (Herting et al, 1994).…”