(446a) Controlled Release of Antibiotics for the Treatment of Bacterial Infection

Controlled release of antibiotics has the potential to limit exposure of nonpathogenic bacteria to the drug, thus limiting development of secondary infections and slowing development of antibiotic resistance. For example, periodontitis is often treated with systemic antibiotics; while effective in clearing the disease-causing organisms in the mouth, the process exposes the gut microbiota to high concentrations of these drugs and has been associated with increased rates of antibiotic resistance in the relevant organisms. Here, we describe such a technique to deliver antibiotics in a controlled fashion to treat localized aggressive periodontitis (LAP), a disease caused by Aggregatibacter actinomycetemcomitans (Aa). Not all strains of Aa are pathogenic, but those that are most closely related to disease have been demonstrated to produce more of a protein toxin, leukotoxin (LtxA). Our previous work demonstrated that LtxA is able to disrupt model membranes (liposomes), but only when they contain certain lipids, those with a negative spontaneous curvature. We have used this specific membrane-permeabilizing activity to design a “Trojan horse” delivery system for the controlled release of antibiotics to treat LAP. We have demonstrated that LtxA, at physiologically relevant concentrations, efficiently permeabilizes liposomes composed of 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-methyl (N-methyl-DOPE), and inclusion of cholesterol enhances this effect. Cell culture medium from an LtxA-producing strain mediates release from the liposomes, but cell culture medium from a non-LtxA-producing strain does not. Finally, we found that antibiotic-containing liposomes inhibit growth of the LtxA-producing strain but not the non-LtxA-producing strain. Control liposomes, composed of POPC do not inhibit bacterial growth. Together, our results demonstrate that N-methyl-DOPE liposomes provide a suitable platform for the specific release of antibiotics only in the presence of the specific disease-causing agent.