IV Jornadas Latinoamericanas de Bacteriófagos

Pseudomonas aeruginosa is an opportunistic pathogen responsible for a significant proportion of healthcare-associated infections, and its growing resistance to antibiotics has made treatment and infection control increasingly challenging. This threat has intensified the search for alternative therapeutic strategies, among which phage therapy has re-emerged as a promising approach, with documented success in difficult-to-treat infections, such as chronic otitis caused by multidrug-resistant P. aeruginosa strains. In this study, lytic bacteriophages against P. aeruginosa ATCC 27853 and a pan-resistant clinical isolate were isolated and characterized. The clinical isolate showed resistance to aminoglycosides, third- and fourth-generation cephalosporins, combinations of β-lactams/β-lactamase inhibitors (piperacillin/tazobactam and ceftolozane/tazobactam), fluoroquinolones, and carbapenems. Environmental samples from rivers, streams, and lakes were processed using double-layer agar plaque assays with selective media for Pseudomonas to detect lytic activity. Viral isolates were concentrated, purified, and filtered from lysis plaques over five consecutive days to ensure homogeneous preparations. Eight phages showed lytic activity against strain ATCC 27853, and four maintained lytic activity against the pan-resistant clinical isolate. Genomic analysis of the active phages included genome assembly, annotation, and comparative analysis to identify gene content, predict lifestyle, and detect potential virulence or antibiotic resistance genes. These analyses supported the classification of the isolates as strictly lytic phages, suitable for therapeutic development.