Eduction of Both Planktonic and Biofilm Bacteria in a Pig Skin Explant Model by a Topical LAE Formulation

Introduction: We evaluated the effects of novel formulations containing lauryl arginate ethyl ester (LAE) on killing both planktonic bacteria and mature biofilms of bacteria grown on an ex vivo model of chronic skin wounds.

Materials and Methods: Sterile porcine skin explants with deep partial thickness wounds were inoculated with 50l of Pseudomonas aeruginosa (PA01) or Staphylococcus aureus (SA113) suspension culture containing 4 x 106 CFU then incubated at 37°C for 30 min followed by exposure to one of four treatments (PBS, Vehicle gel, 5% LAE gel and 1% LAE gel). Total bacterial CFU were measured after 24 and 48 hours of incubation at 37C. For biofilm experiments, inoculated explants were cultured for 3 days at 37C to develop mature biofilms then wiped with sterile gauze and exposed to the same four test treatments, and total and biofilm bacterial CFU were measured after 1, 2, and 3 days of exposure.

Results: The 5% LAE formulation produced total killing of both PAO1 and SA planktonic bacteria on pig skin explants. The 1% LAE formulation killed SA planktonic bacteria, but only reduced the levels of total PAO1 bacteria about 3-logs after 1, 2 and 3 days compared to PBS treatment. For mature PA01 biofilms, 5% LAE formulation reduced biofilm CFU about 2-logs on the first day then completely killed the total and biofilm PAO1 bacteria after 2 and 3 days of treatment. The 1% LAE formulation was less effective, and reduced the levels of total PAO1 bacteria about 2-logs by the third day, while it completely killed the biofilms from the first day. The 5% LAE formulation completely killed the total bacteria and biofilms of SA113 on the second and third days, while the 1% LAE formulation completely killed only the biofilm on days 2 and 3.

Conclusions: The 5% LAE formulation totally kills both planktonic and biofilm of PA01 and SA113 bacteria, while the 1% LAE formulation is less effective.