Infiltrating MDR Gram-negative bacteria using an innovative antibiotic-assisted translocation approach

"Drug-resistant infections are already responsible for a significant number of deaths globally each year. Of these, those caused by MDR Gram-negative pathogens such as Enterobacteriaceae, Acinetobacter, Pseudomonas and _Klebsiella_ are amongst the most serious health threats. Gram-negative bacteria, in general, are intrinsically resistant to a significant number of antibiotics and can cause infections that are difficult to treat. A major drawback that has stalled progress on nearly all new classes with potential for activity against Gram-negative bacteria has been achieving whole-cell activity. Gram-negative bacteria have built-in defence mechanisms, including an outer and inner cell membrane that is not easily penetrated by drugs and/or antibiotics, and multiple cell-surface efflux pumps that can expel drugs that do manage to cross the cell membrane, out of the cell before it has the chance to kill the bacteria.

Enhancing the antibacterial activity of current or new antibiotics against MDR Gram-negative pathogens would provide considerable value to these otherwise effective and beneficial antibiotics. Therefore there exists a need for strategies which will overcome the defence mechanisms of bacteria to allow these antibiotics to have a sustained therapeutic effect and the present project aims to provide a means by which to bypass these bacterial defence mechanisms in MDR Gram-negative pathogens.

An innovative non-siderophore-based approach to mediate fast facilitated delivery of an antibacterial agent into the cytoplasm of bacteria, thereby bypassing the outer membrane and efflux mechanism(s) has been discovered. It employs an essential and non-redundant uptake pathway that is highly conserved and constitutively expressed across Gram-negative bacteria (and Gram-positive) and is highly selective for a specific carbohydrate that is essential for bacterial growth and survival. Selective enzymatic cleavage within the cytoplasm results in the release of the active anti-bacterial agent.

The project will aim to demonstrate that combinations of this antibiotic-assisted translocation platform technology with drugs against two novel but validated bacterial targets that have been terminated due to poor whole-cell activity caused by bacterial defence mechanisms, will provide an effective solution in significantly lowering the dose and MIC (minimum inhibitory concentration) that is required to inhibit bacterial growth of multiple types of MDR bacteria with these novel inhibitors. These targets include LPxC, the enzyme responsible for the first committed step in the biosynthesis of lipid A, a key component of the outer membrane, as well as MurC, the first of four amino-acid adding enzymes involved in the biosynthesis of the peptidoglycan,"