Evaluación de cambios fenotípicos en cepas de Salmonella Infantis tras la adquisición de resistencia al bacteriófago 35fd

Abstract

This research focuses on *Salmonella enterica* serotype Infantis (SI), a globally significant zoonotic pathogen primarily associated with poultry products and characterized by its increasing resistance to third-generation antibiotics. This resistance capability, facilitated by the presence of a megaplasmid, has contributed to the pathogen's expansion and its displacement of other, more common serotypes. Although bacteriophages offer a promising control alternative, bacteria can develop resistance to them, complicating elimination efforts.

The study evaluated phenotypic changes in three SI strains exposed to the Felix35fd bacteriophage by analyzing growth curves, megaplasmid presence, and resistance to various antibiotics. Two mutant strains (GC2 and PO2) were obtained, both exhibiting a significant increase in antibiotic resistance—up to eight times the initial concentration.

These findings underscore the role of the megaplasmid in bacterial survival and adaptation under bacteriophage-induced pressure. The study provides valuable insights into the evolution of bacterial resistance and may help inform the development of more effective strategies for controlling and eliminating *Salmonella* Infantis in public health and poultry production contexts.