tachyplesin-peptide--tachypleus-tridentatus and pexiganan

Tachyplesin I is a 17-amino-acid cationic antimicrobial peptide (AMP) with a typical cyclic antiparallel β-sheet structure that is a promising therapeutic for infections, tumors, and viruses. To date, no bacterial resistance to tachyplesin I has been reported. To explore the safety of tachyplesin I as an antibacterial drug for wide clinical application, we experimentally induced bacterial resistance to tachyplesin I by using two selection procedures and studied the preliminary resistance mechanisms. Aeromonas hydrophila XS91-4-1, Pseudomonas aeruginosa CGMCC1.2620, and Escherichia coli ATCC 25922 and F41 showed resistance to tachyplesin I under long-term selection pressure with continuously increasing concentrations of tachyplesin I. In addition, P. aeruginosa and E. coli exhibited resistance to tachyplesin I under UV mutagenesis selection conditions. Cell growth and colony morphology were slightly different between control strains and strains with induced resistance. Cross-resistance to tachyplesin I and antimicrobial agents (cefoperazone and amikacin) or other AMPs (pexiganan, tachyplesin III, and polyphemusin I) was observed in some resistant mutants. Previous studies showed that extracellular protease-mediated degradation of AMPs induced bacterial resistance to AMPs. Our results indicated that the resistance mechanism of P. aeruginosa was not entirely dependent on extracellular proteolytic degradation of tachyplesin I; however, tachyplesin I could induce increased proteolytic activity in P. aeruginosa Most importantly, our findings raise serious concerns about the long-term risks associated with the development and clinical use of tachyplesin I.

Topics: Aeromonas hydrophila; Amikacin; Anti-Bacterial Agents; Antimicrobial Cationic Peptides; Cefoperazone; DNA-Binding Proteins; Dose-Response Relationship, Drug; Drug Resistance, Bacterial; Escherichia coli; Microbial Sensitivity Tests; Mutation; Peptides, Cyclic; Proteolysis; Pseudomonas aeruginosa; Selection, Genetic; Ultraviolet Rays

Protegrins are broad spectrum antibiotic peptides isolated from porcine leukocytes. In this study, we (i) examine the sensitivity of Gram-negative, anaerobic periodontal pathogens to synthetic protegrins; (ii) determine the relative potencies of protegrin congeners against these bacteria; and (iii) compare the potency of protegrins with other antibiotic peptides, including magainin MSI-78, tachyplesin I, cecropin P1, human defensins HNP-1-3, and clavanin A. Synthetic L- and D-enantiomers of protegrin 1 (PG-1 and D-PG-1, respectively), and L-enantiomers of protegrins 2, 3 and 5 (PG-2, PG-3 and PG-5) were tested against Fusobacterium nucleatum, and black-pigmented organisms including Porphyromonas gingivalis and Prevotella intermedia. Strains of both F. nucleatum and the black-pigmented organisms were sensitive to PG-1, and exhibited mean ED99 of 2.2-2.3 micrograms/ml and 3.4-9.9 micrograms/ml, respectively. The D-form was statistically more potent than the L-form against these oral anaerobes, and although this difference in potency is unlikely to be of decisive therapeutic significance, the D-form may be of value given ability to resist microbial and host-derived proteases. PG-1 was more potent than magainin, tachyplesin, cecropin, defensins and clavanin under test conditions. Hypertonic salt concentrations and heat-inactivated serum were found to be inhibitory to the bactericidal activity of PG-1. PG-1 was found to induce morphologic alterations in the ultrastructural appearance of F. nucleatum consistent with damage to the bacterial membranes. We conclude that protegrins may be useful antimicrobial agents in therapy against Gram-negative anaerobic bacteria believed to be involved in chronic, adult forms of periodontal infections.

Topics: alpha-Defensins; Amino Acid Sequence; Animals; Anti-Bacterial Agents; Antimicrobial Cationic Peptides; Blood Proteins; Cell Membrane; Colony Count, Microbial; Defensins; DNA-Binding Proteins; Fusobacterium nucleatum; Gram-Negative Anaerobic Bacteria; Magainins; Microbial Sensitivity Tests; Molecular Sequence Data; Peptides; Peptides, Cyclic; Porphyromonas gingivalis; Prevotella intermedia; Proteins; Swine; Toxicity Tests; Xenopus Proteins