title: Peptides from American alligator plasma are antimicrobial against multi-drug resistant bacterial pathogens including Acinetobacter baumannii.
abstract: Our group has developed a new process for isolating and identifying novel cationic antimicrobial peptides from small amounts of biological samples. Previously, we identified several active antimicrobial peptides from 100 μl of plasma from Alligator mississippiensis. These peptides were found to have in vitro antimicrobial activity against Pseudomonas aeruginosa and Staphylococcus aureus. In this work, we further characterize three of the novel peptides discovered using this process: Apo5, Apo6, and A1P.
  
  
  
  We examined the activity of these peptides against multi-drug resistant strains and clinical isolates of common human pathogens. We investigated their structural characteristics using circular dichroism and tested for membrane disruption and DNA binding. These peptides were found to have strong in vitro activity against multi-drug resistant and clinically isolated strains of S. aureus, Escherichia coli, P. aeruginosa, and Acinetobacter baumannii. Apo5 and Apo6, peptides derived from alligator apolipoprotein C-1, depolarized the bacterial membrane. A1P, a peptide from the serpin proteinase inhibitor, did not permeabilize membranes. Performing circular dichroism analysis, Apo5 and Apo6 were found to be predominantly helical in SDS and TFE buffer, while A1P has significantly different structures in phosphate buffer, SDS, and TFE. None of these peptides were found to be hemolytic to sheep red blood cells or significantly cytotoxic up to 100 μg/ml after 24 h exposure.
  
  
  
  Overall, we suggest that Apo5 and Apo6 have a different mode of action than A1P, and that all three peptides make promising candidates for the treatment of drug-resistant bacteria, such as A. baumannii.
authors.affiliation: School of Systems Biology, George Mason University, Manassas, VA, USA.
authors.forename: Stephanie M
authors.initials: SM
authors.lastname: Barksdale
authors.affiliation: College of Science, George Mason University, Manassas, VA, USA.
authors.forename: Evelyn J
authors.initials: EJ
authors.lastname: Hrifko
authors.affiliation: National Center of Biodefense and Infectious Diseases, George Mason University, 10920 George Mason Cir, 10920 George Mason Circle, MSN 1H8, Manassas, VA, 20110, USA.|Present Address: STCube Pharmaceuticals, Inc., 401 Professional Dr. Suite 108, Gaithersburg, MD, 20879-3429, USA.
authors.forename: Ezra Myung-Chul
authors.initials: EM
authors.lastname: Chung
authors.affiliation: School of Systems Biology, George Mason University, Manassas, VA, USA. mvanhoek@gmu.edu.|National Center of Biodefense and Infectious Diseases, George Mason University, 10920 George Mason Cir, 10920 George Mason Circle, MSN 1H8, Manassas, VA, 20110, USA. mvanhoek@gmu.edu.
authors.forename: Monique L
authors.initials: ML
authors.lastname: van Hoek
mesh_terms: D040981:Acinetobacter baumannii / Q000187:drug effects*; D000489:Alligators and Crocodiles / Q000097:blood*; D000595:Amino Acid Sequence; D000818:Animals; D000900:Anti-Bacterial Agents / Q000097:blood / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D023181:Antimicrobial Cationic Peptides / Q000097:blood* / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects; D024901:Drug Resistance, Multiple, Bacterial; D004912:Erythrocytes / Q000187:drug effects; D004926:Escherichia coli / Q000187:drug effects; D008826:Microbial Sensitivity Tests; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011550:Pseudomonas aeruginosa / Q000187:drug effects; D012756:Sheep; D013211:Staphylococcus aureus / Q000187:drug effects
chemical_list: D000900:Anti-Bacterial Agents; D023181:Antimicrobial Cationic Peptides
keywords: Acinetobacter baumannii; Alligator mississippiensis; Antimicrobial peptides; Escherichia coli; Multi-drug resistant bacteria; Staphylococcus aureus