Antibiotic combination therapies against drug resistant Gram-negative pathogens: Synergy with the innate immune system, effects on the emergence of heteroresistance and treatment of biofilms.
At present antibiotic resistance is a fast growing problem in human society1. During the last decades a continuous rise of multi-drug resistant bacterial pathogens has occurred. Among the most problematic pathogens for which new antibacterial strategies are needed are the so-called “ESKAPE” organisms2. Of these, the drug-resistant forms of the Gram-negative pathogens Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species (Enterobacterciaceae) have recently been placed at the top of the global Priority Pathogens List (PPL) as published by the World Health Organization (WHO)3. One of the most significant barriers in developing new antibacterial agents against Gram-negative pathogens is the presence of their outer membrane4. This cellular barrier represents an obstacle towards applying innovations in the field of antibiotic development. A promising approach is to identify compounds that can act synergistically. Specifically, the effect of combining compounds (or components of the human immune system) that destabilize the Gram-negative outer membrane with antibiotics that target the bacterial cell wall and/or inner membrane.
Besides the emergence of drug-resistant bacteria another serious problem in modern medicine is the ability of pathogens to form biofilms. A promising approach is to attempt to permeabilize the biofilm matrix5. Potentially permeabilization can be combined with previously found synergistic combinations of Gram-positive selective antibiotics and outer membrane destabilizing compounds for optimal treatment of infections.
Moreover, persisters (survivors at relatively high antibiotic concentrations that can grow out when the antibiotic concentration drops) and heteroresisters (pathogenic cells that can still grow slowly at concentrations close to MIC values of the antibiotic applied) can occur when using one antibiotic6 It will be attempted to visualize resistance development by means of widefield microscopy, microfluidics and potentially confocal laser scanning microscopy. We hope to identify compound mixtures capable of eradicating, or greatly reducing, the number of heteroresisters and/or persisters.
Developing promising combination therapies against gram-negative pathogens, predominantly members of the ESKAPE pathogens, with the potential to reduce heteroresister and persister occurrence as well as increase the effectiveness of biofilm treatment.
Cloning (USER, Gibson), PCR, Protein expression, SDS-PAGE, Western blotting, His-taq purification, HPLC, Mass spectrometry, Checkerboard assay, Biofilm assay, Widefield microscopy, Microfluidics.
- World Health Organization. ANTIMICROBIAL RESISTANCE Global Report on Surveillance.; 2014.
- Ventola CL. The Antibiotic Resistance Crisis Part 1: Causes and Threats. 2015;40(4).
- Tacconelli E, Magrini N, Kahlmeter G, Singh N. Global Priority List of Antibiotic-Resistant Bacteria To Guide Research, Discovery, and Development of New Antibiotics. World Heal Organ. 2017.
- Silhavy TJ, Kahne D, Walker S. The Bacterial Cell Envelope. Cold Spring Harb Perspect Biol. 2010. doi:10.1101/cshperspect.a000414.
- Dufour D, Leung V, Lévesque CM. Bacterial biofilm: structure, function, and antimicrobial resistance. Endod Top. 2010;22(1):2-16. doi:10.1111/j.1601-1546.2012.00277.x.
- Sorg R a, Veening J-W. Microscale insights into pneumococcal antibiotic mutant selection windows. Nat Commun. 2015;6:8773. doi:10.1038/ncomms9773.
B. subtilis agar-air interface biofilm.