Pseudomonas aeruginosa (Pa) is the main pathogen responsible for chronic infection in cystic fibrosis patients. Antibiotic tolerant Pa cells (persisters), including Viable But Non-Culturable (VBNC) forms, severely hamper infection eradication. Some research data suggest that VBNC cells can be induced by treatment with low antibiotic doses. The aim of this project is to verify this hypothesis and identify the antibiotics that may be involved in inducing VBNC to grow. Researchers will assess the VBNC-inducing ability of different antibiotics studying Pa biofilms exposed to subinhibitory concentrations. These biofilms will be monitored for six months and culturable and non-culturable viable subpopulations will be determined by plate count, qPCR, and flow cytometry. A species-specific flow cytometry assay for the detection of all live Pa forms, including VBNC not detectable by the routine culture assays, will be developed. This assay will be based on RNA probes targeting species-specific mRNA or rRNA sequences designed to detect Pa VBNC. Finally, researchers will investigate the anti-persister activity of novel compound combinations that will include an antibiotic currently used and an anti-persister molecule (among those described in research as potentially active against PA persisters). The perspective is to get new insights about Pa persistence in pulmonary CF infection, to improve tools for effective microbiological diagnosis and to achieve more effective antibiotic strategies. Researchers will continue in this way their previous project FFC#13/2017.