Evidence of cefiderocol-persistence in Pseudomonas aeruginosa in vitro biofilms and in a murine infection model

Background Persistent and viable but non-culturable (VBNC) Pseudomonas aeruginosa cells hamper the eradication and contribute to the recurrence of biofilm-related infections, especially in cystic fibrosis (CF) patients, often experiencing difficult-to-treat lung infections. The siderophore-cephalosporin cefiderocol, which hijacks bacterial iron-uptake systems, has emerged as a last-resort antibiotic against antibiotic-resistant Gram-negative bacteria and represents a desirable therapeutic option; however, there is still limited information about its impact on bacterial persisters. Methods P. aeruginosa biofilms were exposed to either tobramycin, ceftazidime, or cefiderocol at their minimum biofilm eradication concentrations under iron depletion in a rich or minimal medium. The bacterial survivors were quantified by combining cultural enumerations, quantitative PCR and confocal microscopy, to detect both culturable and VBNC cells. To extend these observations in vivo , a murine model of P. aeruginosa lung infection was employed, and bacterial burden and VBNC frequency were assessed following antibiotic treatment. Results A higher amount of culturable P. aeruginosa cells was recovered after cefiderocol challenge (∼10 5 CFU/ml) compared to tobramycin and ceftazidime (10 3 -10 4 CFU/ml). Notably, it induced a significantly lower proportion of VBNC cells (∼85.2%) than the aminoglycoside (98.95%) or ceftazidime (95.80%). Consistently, cefiderocol exposure resulted in a higher bacterial survival in vivo , but in a lower frequency of VBNC subpopulation (71.89%) compared to tobramycin (81,58%). Conclusions Overall, these findings emphasize the capacity of P. aeruginosa to withstand treatment with cefiderocol and highlight the need to account for the roles of bacterial persisters and VBNC cells in the recurrence of chronic infections, particularly among CF patients.