Nanoparticles Promote Bacterial Antibiotic Tolerance via Inducing Hyperosmotic Stress Response

With the rapid development of nanotechnology, nanoparticles (NPs) are widely used in all fields of life. Nowadays, NPs have shown extraordinary antimicrobial activities and become one of the most popular strategies to combat antibiotic resistance. Whether they are equally effective in combating bacterial persistence, another important reason leading to antibiotic treatment failure, remains unknown. Persister cells are a small subgroup of phenotypic drug-tolerant cells in an isogenic bacterial population. Here, various types of NPs are used in combination with different antibiotics to destroy persisters. Strikingly, rather than eradicating persister cells, a wide range of NPs promote the formation of bacterial persistence. It is uncovered by PCR, thermogravimetric analysis, intracellular potassium ion staining, and molecular dynamics simulation that the persister promotion effect is achieved through exerting a hyperosmotic pressure around the cells. Moreover, protein mass spectrometry, fluorescence microscope images, and SDS-PAGE indicate NPs can further hijack cell osmotic regulatory circuits by inducing aggregation of outer membrane protein OmpA and OmpC. These findings question the efficacy of using NPs as antimicrobial agents and raise the possibility that widely used NPs may facilitate the global emergence of bacterial antibiotic tolerance.