Resensitizing Resistant Bacteria to Antibiotics

摘要

During the performance period, we screened a phage display library of approximately 5x109 individual 12-mer peptides for specific binding to a pentaglycine substrate. The pentaglycine substrate is a synthetic mimetic of the cross bridge found in the cell walls of Staphylococcus aureus. We purified, sequenced, and identified 40 candidate peptides that bound the pentaglycine target higher than bovine serum albumin control screens as determined by enzyme-linked immunosorbant assays (ELISA). Of these 40 candidates, we further screened the phage displaying the top 10 tightest binding peptides against S. aureus in a spun-ELISA assay. We found two peptides, No. 5 and No. 39, bound to whole staphylococcal cells as well as pentaglycine. Next, we added the phage displaying No. 39 or a randomized version of No. 39 to growing staphylococci and showed that No. 39, but not the randomized version, significantly slowed growth of the bacteria. We next chemically synthesized all 10 of our candidate peptides, randomized versions of all 10, and fluorescent-labeled versions of all 10. Unfortunately, none of the peptides alone displayed an inherent antimicrobial capacity but some showed synergy with oxacillin against methicillin-resistant staphylococci as well as synergy with vancomycin against vancomycin-resistant staphylococci. We then used fluorescent derivatives of the peptides to show binding to the staphylococcal surface. Finally, we conjugated one peptide (No. 2) to vancomycin through a thiol group and showed it had similar, but not better, properties than unlabeled vancomycin.