Phages targeting highly prevalent Greek multidrug-resistant Pseudomonas aeruginosa clinical isolates: In vitro and in...

Metallo-β-lactamase-producing Pseudomonas aeruginosa (MBL-PA) poses a major therapeutic challenge. In search of alternative therapeutic approaches, bacteriophages against MBL-PA were isolated from environmental and clinical samples and thoroughly characterized. Samples from a sewage treatment plant (n = 50), rectal swabs (n = 50), and stool samples (n = 10) from patients were screened. Genomic features, microbiological properties, and growth-inhibition kinetics were determined for all isolated phages. The in vivo pharmacokinetics and therapeutic efficacy of intranasally administered phages, given alone or in combination with intraperitoneally administered amikacin, were evaluated in a murine lung infection model using a clinical MBL-PA isolate. The phages exhibited variable lytic activity against 23-70% of the isolates. The median (range) adsorption rate, time, latent phase, and burst size were 93 (87-95) %, 4 (2-12) min, 30 (20-40) min, and 73 (48-235) PFU/infected cell, respectively. All isolated phages strongly inhibited the growth of their host strains with a median (range) of 88 (56-128)% growth inhibition. In vivo, phage titers reached up to 10⁷ PFU/lung in lung tissue and in bronchoalveolar lavage fluid, whereas no phages were detected in blood. Combination therapy with amikacin significantly reduced the bacterial burden by ≥ 2.8 log₁₀ CFU/lung compared with monotherapies. Strong lytic activity and a relatively broad spectrum within the tested isolate collection were observed among the isolated phages against MBL-producing P. aeruginosa isolates. Selected phages exhibited high lytic activity even at the lowest multiplicity of infection tested, making them promising candidates for further investigation in efforts to control multidrug-resistant P. aeruginosa infections, particularly when combined with antibiotics.