Effects of different surfactant preparations on bacterial growth in vitro

Several lines of evidence suggest that surfactant and surfactant proteins may have direct effects on inhaled bacteria and are able to interact with lung defence mechanisms in many ways. We examined the effect of three different surfactant preparations (Alveofact, Survanta and Exosurf) approved for treatment of the infant respiratory distress syndrome on different strains of Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis and Streptococcus agalactiae which are important neonatal pathogens and on Legionella pneumophila serogroup I as a frequent cause of pneumonia in adults. Addition of Survanta to saline seemed to delay the reduction of viable bacteria in sterile saline and induced a considerably accelerated growth of all examined E. coli strains. As opposed to this, addition of surfactant did not influence the kinetics of bacterial growth in brain-heart infusion or buffered yeast extract both with the exception of Exosurf which exerted an inhibitory effect on the multiplication of group B streptococci. Though the exact mechanisms underlying these effects remain to be determined, the influence of surfactant therapy on the growth of bacteria within the respiratory tract should be taken into account.