Genomic Characterization of Clinical Staphylococcus aureus Isolates from Ecuador Reveals Diverse Lineages and Genomic Similarity Among Sequence Type 2625 Isolates

Staphylococcus aureus is characterized by substantial genomic diversity, with lineages differing in antimicrobial resistance, virulence-associated determinants, and accessory genetic content. However, genomic data from Ecuador remain comparatively limited. Here, we characterized five clinical S. aureus isolates recovered in Ibarra, Ecuador, using phenotypic antimicrobial susceptibility testing and whole-genome sequencing, and compared them with publicly available Ecuadorian genomes. The isolates represented four sequence types (ST8, ST30, ST72, and ST2625), including four MRSA isolates and one MSSA isolate. Whole-genome analysis identified differences in antimicrobial resistance determinants, virulence-associated genes, and replicons, while phenotypic susceptibility profiles generally corresponded with the detected resistance traits. The Ecuadorian collection showed a diverse population structure, with ST8 predominating. Placement within globally circulating lineages showed that the ST8 isolates clustered with USA300-LV (CA12), the ST30 isolate with G2-Sg2-Pr, and the ST72 isolate with clade B. A focused phylogenomic analysis of ST2625 showed limited genomic divergence among Ecuadorian and international isolates, with broadly similar resistance and virulence-associated profiles. These findings add genomic data from northern Ecuador and illustrate variation in the genetic composition of circulating S. aureus lineages. Continued genomic surveillance across additional geographic settings may help clarify the distribution and diversity of S. aureus in the country.