Objective Surfactant protein B (SP-B) has been shown to kill bacteria by permeabilizing bacterial membranes. However, antimicrobial activity of native SP-B is inhibited by surfactant phospholipids to a greater degree than synthetic SP-B derivatives.¹ We investigate the bactericidal effects of Surfaxin® (lucinactant), a wholly-synthetic surfactant that contains KL4, a 21-amino acid peptide that functionally mimics SP-B.

Methods E. coli and S. aureus working bacterial cultures at a concentration of 104 CFU were prepared and incubated at 37°C in the presence of Surfaxin, Survanta® (beractant; Abbott Nutritionals) as a reference comparator, 0.9% saline (negative control), or ciprofloxacin (positive control). Bacterial growth was assessed at 0, 24, 48, and 72 hours.

Results For media exposed to Surfaxin, there was no growth of S. aureus or E. coli at any time point. For media exposed to Survanta, there was growth of E. coli at all time points, but no growth of S. aureus at any time points. In the saline control there was growth of all bacteria at all time points, while there was no growth of any bacteria at all time points in the ciprofloxacin controls.

Conclusion Surfaxin is bactericidal for both E. coli and S. aureus, whereas Survanta is bactericidal only for S. aureus. Surfaxin may protect against pulmonary infection from both gram positive and gram negative organisms aspirated during birth.

Supported by Discovery Labs.

1. Ryan MA, et al. J Immunol 2006;176:416–425.