Three Pseudomonas aeruginosa (Pa) strains characterized by different T (Tobramycin) resistance mechanisms – two clinical CF strains and the PAO1 reference strain – were used in the study. Researchers exposed 48h in vitro biofilms to different stress conditions: non-nutrient broth (NN); high salt concentrations; catabolite accumulation; each unsupplemented or supplemented with subinhibitory T concentrations. Biofilms were tested for 5 months (Pa30 and PaAR86) or 7 days (PAO1) for VBNC cell content using culture methods, qPCR (3) and flow cytometry after live/dead staining. It was shown i) a variable and strain-specific effect of T in inducing the VBNC phenotype after long-term exposure; ii) its involvement in the development of VBNC or persistent culturable forms in presence of typical CF-related stress conditions; and iii) the need for a culture-independent microbiological diagnosis to properly monitor Pa colonization of CF lung. The study of the factors contributing to the development and persistence of Pa VBNC forms in CF lung biofilms will be improved by testing six further anti-Pseudomonas drugs in the extension project FFC#16/2019). A species-specific flow cytometry protocol suitable for the routine diagnosis of Pa infection in CF patients will also be developed.

Congress abstracts

– Mangiaterra G, Cedraro N, Vaiasicca S et al. “Induction of Viable but Non-Culturable Pseudomonas aeruginosa by tobramycin in in vitro biofilms” 33rd Meeting of the Italian Society of General Microbiology and Microbial Biotechnology (SIMGBM), June 2019
– Mangiaterra M, Manso E, Cirilli N et al. “Effectiveness of qPCR for reliable Pseudomonas aeruginosa cystic fibrosis lung infection diagnosis” International Congress of Microbiology and Infectious Disease (ICMID), Rome, November 2019, Invited speaker
– Mangiaterra G, Cedraro N, Laudadio E et al. “Anti-persistence activity of the natural alkaloid berberine against Pseudomonas aeruginosa” Meeting of the Italian Society of Chemistry-Marche region section, September 2019
– Mangiaterra G, Cedraro N, Citterio B et al. “Induction of Viable but not-culturable P. aeruginosa in in vitro Biofilms. Role of sub-inhibitory antibiotic concentrations” Biofilm 8, Aarhus University, Aarhus C, Denmark, 27-29 May 2018