PROJECT SUMMARY
The continued rise in the number multidrug resistant (MDR) bacterial infections, especially those caused by
Gram-negative pathogens, coupled with the dearth of novel antibiotics being FDA approved in the past 3 decades
has led to a dire situation that could result in millions of deaths per year worldwide if current trends continue.
MDR Pseudomonas aeruginosa (PA), a Gram-negative bacterium, is one of leading causes of nosocomial
infections and has been designated as a “Serious Threat” by the CDC due to lack of viable treatment options.
Two barriers that must be overcome when treating MDRPA infections are wide-spread resistance to currently
prescribed antibiotics with similar mechanisms of action and poor accumulation of the antibiotic in the cell due
to its additional outer membrane (OM) and promiscuous efflux pumps. Therefore, antibiotics that target
unexplored cellular targets in MDRPA and methods for improved antibiotic delivery to those targets must be
developed. This work proposes to first probe ATP synthase, an essential protein for all life, as an underexplored
target for antibiotic development by modifying the known anti-tubercular drug bedaquiline. By comparing residue
differences in the BDQ binding site between Mycobacterium tuberculosis and PA, bedaquiline-like molecules
capable of inhibiting PA ATP synthase selectively will be designed. This work will also give insight into the role
of ATP synthase inhibition in antibiotic drug discovery. Next, a cleavable adjuvant-antibiotic hybrid strategy will
be developed to overcome the OM penetration problem in PA. The OM is made up of an asymmetric bilayer of
lipopolysaccharides, porins, and substrate channels, which severely limits small molecule entry into the cell by
size and charge. It has been recently demonstrated that polycationic molecules, such as aminoglycosides and
bisamidines, are able to cross the OM by self-promoted uptake and are able to act as adjuvants to promote the
uptake of other antibiotics. A cleavable bisamidine-antibiotic drug delivery system will be synthesized that
capitalizes on the synthetic bisamidine being able to promote diffusion of the tethered antibiotic across the OM
and the antibiotic being released upon enzymatic linker cleavage in the periplasm. Using a covalent but cleavable
linker system ensures cellular uptake of the antibiotic without reducing antibiotic activity once in the cell. The
work proposed herein will not only produce new and highly efficacious small molecules to treat MDRPA
infections, it will also develop a robust and modifiable method for delivering a wide variety of antibiotics that
cannot cross the OM on their own to the interior of the cell. This will ultimately increase the number of antibiotics
capable of treating these infections and help to combat the growing number of resistant bacteria clinically.
