Sensitization of Staphylococcus aureus to methicillin and other antibiotics in vitro and in vivo in the presence of HAMLET

Research output: Contribution to journalArticle

Abstract

HAMLET (human alpha-lactalbumin made lethal to tumor cells) is a protein-lipid complex from human milk with both tumoricidal and bactericidal activities. HAMLET exerts a rather specific bactericidal activity against some respiratory pathogens, with highest activity against Streptococcus pneumoniae, but lacks activity against most other bacterial pathogens, including Staphylococci. Still, ion transport associated with death in S. pneumoniae is also detected to a lower degree in insensitive organisms. In this study we demonstrate that HAMLET acts as an antimicrobial adjuvant that can increase the activity of a broad spectrum of antibiotics (methicillin, vancomycin, gentamicin and erythromycin) against multi-drug resistant Staphylococcus aureus, to a degree where they become sensitive to those same antibiotics, both in antimicrobial assays against planktonic and biofilm bacteria and in an in vivo model of nasopharyngeal colonization. We show that HAMLET exerts these effects specifically by dissipating the proton gradient and inducing a sodium-dependent calcium influx that partially depolarizes the plasma membrane, the same mechanism induced during pneumococcal death. These effects results in an increased cell associated binding and/or uptake of penicillin, gentamicin and vancomycin, especially in resistant stains. Finally, HAMLET inhibits the increased resistance of methicillin seen under antibiotic pressure and the bacteria do not become resistant to the adjuvant, which is a major advantageous feature of the molecule. These results highlight HAMLET as a novel antimicrobial adjuvant with the potential to increase the clinical usefulness of antibiotics against drug resistant strains of S. aureus.

Details

Authors
External organisations
  • University at Buffalo
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Immunology in the medical area

Keywords

  • Animals, Anti-Bacterial Agents, Biofilms, Boron Compounds, Calcium Signaling, Drug Synergism, Gentamicins, Lactalbumin, Membrane Potentials, Methicillin, Methicillin Resistance, Methicillin-Resistant Staphylococcus aureus, Mice, Microbial Sensitivity Tests, Microbial Viability, Nasopharynx, Oleic Acids, Penicillins, Respiratory Tract Infections, Staphylococcal Infections, Uncoupling Agents, Vancomycin
Original languageEnglish
Article numbere63158
JournalPLoS ONE
Volume8
Issue number5
Publication statusPublished - 2013
Publication categoryResearch
Peer-reviewedYes
Externally publishedYes