oprM as a new target for reversion of multidrug resistance in Pseudomonas aeruginosa by antisense phosphorothioate oligodeoxynucleotides

Multidrug-resistant Pseudomonas aeruginosa (MDR-PA) is one of the leading Gram-negative organisms associated with nosocomial infections. The increasing frequency of MDR-PA has represented a huge challenge in conventional antibacterial therapy. The loss of effectiveness of commonly used antibiotics calls for the immediate need to develop an alternative strategy for combating MDR-PA infections. The multiantibiotic resistance of MDR-PA is largely attributable to the production of multidrug efflux pumps, MexAB-OprM. OprM forms the antibiotic-ejecting duct and plays a crucial role in exporting incoming chemotherapeutic agents across the membranes. Disruption of the OprM expression may inhibit the function of multidrug efflux pumps and lead to restoration of MDR-PA susceptibility to antibiotics. In this study, we developed a novel anion liposome for encapsulating and delivering specific anti-oprM phosphorothioate oligodeoxynucleotide (PS-ODN617) and polycation polyethylenimine (PEI) complexes. The additions of the encapsulated anti-oprM PS-ODN617/PEI to MDR-PA isolates caused a significant reduction of oprM expression and inhibition of MDR-PA growth in the presence of piperacillin in a concentration-dependent manner. The encapsulated PS-ODN617 treatment also reduced minimal inhibitory concentrations of five most commonly used antibiotics to the sensitive margin values on MDR-PA clinical isolates, respectively. The results of present study firstly indicate that PS-ODN targeted to oprM can significantly restore the susceptibility of MDR-PA to existing antibiotics, which appears to be a novel strategy for treating MDR-PA infections.