Overcoming Multidrug Resistance and Biofilms of Pseudomonas aeruginosa with a Single Dual-Function Potentiator of β-Lactams.

Clinicians prescribe hundreds of millions of β-lactam antibiotics to treat the majority of patients presenting with bacterial infections. Patient outcomes are positive unless resistant bacteria, such as , are present. has both intrinsic and acquired antibiotic resistance, making clinical management of infection a real challenge, particularly when these bacteria are sequestered in biofilms. These problems would be alleviated if, upon the initial presentation of bacterial infection symptoms, clinicians were able to administer an antibiotic that kills both susceptible and otherwise resistant bacteria; and also eradicates biofilms. As the most common class of antibiotics, β-lactams could be used in a new drug if the leading causes of β-lactam antibiotic resistance - permeation barriers from lipopolysaccharide, efflux pumps, and β-lactamase enzymes - were also defeated. Success may be possible with a discovery made in our laboratory. Against and their biofilms, the potency of β-lactam antibiotics is restored with 600-Da branched polyethylenimine (600-Da BPEI). Checkerboard assays using microtiter plates demonstrate the potentiation of piperacillin, cefepime, meropenem, and erythromycin antibiotics. Growth curves demonstrate the bacteriostatic characteristic of 600-Da BPEI in synergy with piperacillin against antibiotic resistant . Scanning electron microscopy (SEM) was used to confirm that the combination treatment leads to abnormal morphology. Data collected with isothermal titration calorimetry and fluorescence spectroscopy demonstrate a mechanism of action in which potentiation at low concentrations of 600-Da BPEI reduces diffusion barriers from lipopolysaccharides without disrupting the outer membrane itself. Coupled with the ability to overcome reduce antibiotic activity created by biofilm exopolymers, targeting anionic sites on lipopolysaccharides and biofilm exopolysaccharides with the same compound provides new opportunities to counter the rise of multidrug resistant infections.