Effect of different surfactants on pulmonary group B streptococcal infection in premature rabbits.
OBJECTIVE
To evaluate the effects of different surfactants on pulmonary infection with group B streptococci in premature rabbits and to examine the effects of different surfactants on pulmonary alveolar macrophage function of newborn rabbits.


METHODS
Preterm and term rabbit pups.


METHODS
Rabbit pups were infected with GBS aerosols followed by intratracheal administration of either calf lung surfactant extract, minced porcine lung surfactant (Curosurf), synthetic surfactant (Exosurf Neonatal), minced bovine lung surfactant (Survanta), human amniotic fluid-derived surfactant, rabbit surfactant, saline vehicle, or no treatment. Intrapulmonary clearance of GBS was determined by comparing bacterial counts in left lungs cultured immediately after aerosol infection with similarly infected lungs analyzed 4 hours after surfactant therapy. Phagocytosis of streptococci was ascertained by microscopic examination of the right lungs fixed in situ at 4 hours. For comparison, an in vitro method was used to measure growth of GBS in the different surfactants.


RESULTS
Preterm animals had a sixfold increase in pulmonary bacterial growth compared with a slight decrease in intrapulmonary GBS in term animals when all were delivered by cesarean section (p < 0.05). In premature rabbits, GBS proliferation was lowest in animals treated with Exosurf Neonatal and highest in animals receiving Curosurf and human amniotic fluid-derived surfactant (p < 0.05). None of the surfactants promoted accelerated growth of GBS in comparison with control animals. Similar growth of GBS was seen in in vitro cultures. Intrapulmonary phagocytosis of GBS in premature pups was not altered by any of the surfactants. In term rabbit pups, the following measures of macrophage population kinetics remained normal at 1 and 24 hours after surfactant administration: viability, cell numbers based on lung lavage, and in vivo incorporation of thymidine.


CONCLUSIONS
Surfactants used in clinical practice do not accelerate the in vivo growth of group B streptococci in the lungs of preterm rabbits. Some surfactants inhibit streptococcal proliferation. The effects of different surfactants are not explained by changes in macrophage function.
Sherman
M P
MP
Department of Pediatrics, University of California, Los Angeles, Medical Center.
Campbell
L A
LA
Merritt
T A
TA
Long
W A
WA
Gunkel
J H
JH
Curstedt
T
T
Robertson
B
B
D000818:Animals; D000831:Animals, Newborn; D001688:Biological Products; D002455:Cell Division / Q000187:drug effects; D004338:Drug Combinations; D005233:Fatty Alcohols / Q000494:pharmacology / Q000627:therapeutic use*; D008171:Lung Diseases / Q000188:drug therapy* / Q000382:microbiology; D016676:Macrophages, Alveolar / Q000187:drug effects* / Q000382:microbiology / Q000473:pathology; D008954:Models, Biological; D010587:Phagocytosis / Q000187:drug effects; D010743:Phospholipids; D010767:Phosphorylcholine; D011092:Polyethylene Glycols / Q000494:pharmacology / Q000627:therapeutic use*; D011663:Pulmonary Surfactants / Q000494:pharmacology / Q000627:therapeutic use*; D011817:Rabbits; D013290:Streptococcal Infections / Q000188:drug therapy* / Q000382:microbiology; D013292:Streptococcus agalactiae / Q000166:cytology / Q000187:drug effects* / Q000254:growth & development / Q000302:isolation & purification
D001688:Biological Products; D004338:Drug Combinations; D005233:Fatty Alcohols; D010743:Phospholipids; D011663:Pulmonary Surfactants; D010767:Phosphorylcholine; D011092:Polyethylene Glycols; C047049:dipalmitoylphosphatidylcholine, hexadecanol, tyloxapol drug combination; C068291:poractant alfa; C072197:beractant