title: Targeting methicillin-resistant Staphylococcus aureus with short salt-resistant synthetic peptides.
abstract: The seriousness of microbial resistance combined with the lack of new antimicrobials has increased interest in the development of antimicrobial peptides (AMPs) as novel therapeutics. In this study, we evaluated the antimicrobial activities of two short synthetic peptides, namely, RRIKA and RR. These peptides exhibited potent antimicrobial activity against Staphylococcus aureus, and their antimicrobial effects were significantly enhanced by addition of three amino acids in the C terminus, which consequently increased the amphipathicity, hydrophobicity, and net charge. Moreover, RRIKA and RR demonstrated a significant and rapid bactericidal effect against clinical and drug-resistant Staphylococcus isolates, including methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-intermediate S. aureus (VISA), vancomycin-resistant S. aureus (VRSA), linezolid-resistant S. aureus, and methicillin-resistant Staphylococcus epidermidis. In contrast to many natural AMPs, RRIKA and RR retained their activity in the presence of physiological concentrations of NaCl and MgCl2. Both RRIKA and RR enhanced the killing of lysostaphin more than 1,000-fold and eradicated MRSA and VRSA isolates within 20 min. Furthermore, the peptides presented were superior in reducing adherent biofilms of S. aureus and S. epidermidis compared to results with conventional antibiotics. Our findings indicate that the staphylocidal effects of our peptides were through permeabilization of the bacterial membrane, leading to leakage of cytoplasmic contents and cell death. Furthermore, peptides were not toxic to HeLa cells at 4- to 8-fold their antimicrobial concentrations. The potent and salt-insensitive antimicrobial activities of these peptides present an attractive therapeutic candidate for treatment of multidrug-resistant S. aureus infections.
authors.affiliation: Department of Comparative Pathobiology, College of Veterinary Medicine, Purdue University, West Lafayette, Indiana, USA.
authors.forename: Mohamed F
authors.initials: MF
authors.lastname: Mohamed
authors.affiliation: Department of Comparative Pathobiology, College of Veterinary Medicine, Purdue University, West Lafayette, Indiana, USA.
authors.forename: Maha I
authors.initials: MI
authors.lastname: Hamed
authors.affiliation: Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana, USA.
authors.forename: Alyssa
authors.initials: A
authors.lastname: Panitch
authors.affiliation: Department of Comparative Pathobiology, College of Veterinary Medicine, Purdue University, West Lafayette, Indiana, USA mseleem@purdue.edu.
authors.forename: Mohamed N
authors.initials: MN
authors.lastname: Seleem
mesh_terms: D023181:Antimicrobial Cationic Peptides / Q000009:adverse effects / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects; D045744:Cell Line, Tumor; D024901:Drug Resistance, Multiple, Bacterial; D006367:HeLa Cells; D006461:Hemolysis / Q000187:drug effects; D006801:Humans; D008248:Lysostaphin / Q000494:pharmacology; D015636:Magnesium Chloride / Q000737:chemistry; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects*; D008826:Microbial Sensitivity Tests; D011994:Recombinant Proteins / Q000009:adverse effects / Q000494:pharmacology*; D012965:Sodium Chloride / Q000737:chemistry; D013212:Staphylococcus epidermidis / Q000187:drug effects*; D020713:Vancomycin Resistance
chemical_list: D023181:Antimicrobial Cationic Peptides; D011994:Recombinant Proteins; D015636:Magnesium Chloride; D012965:Sodium Chloride; D008248:Lysostaphin