P-1789. Emergence of Salmonella enterica serovar Infantis Carrying the IncFIB (K)_1_Kpn3 (pESI-like) Plasmid in Clinical Isolates in Ecuador

Abstract Background Whole-genome sequencing (WGS) has revolutionized Public Health Microbiology and has been used routinely for identification, epidemiological surveillance and monitoring antimicrobial resistance (AMR). In this study, in silico gene detection and clonality analysis identified the presence of multidrug-resistant Salmonella enterica serovar Infantis isolates with extended-spectrum β-lactamase AMR determinants harbored on a megaplasmid (pESI-like plasmid) called IncFIB (K)_1_Kpn3 in the Ecuadorian population.Heatmap of multidrug-resistant strains of Salmonella enterica serovar Infantis.Red = Resistance and yellow = Susceptibility.Plasmid IncFIB (K)_1_Kpn3 diagram in Ecuadorian strains Methods Twelve S. Infantis strains were obtained from urine cultures of patients aged 9 months to 95 years (11 female, 1 male) between 2022-2024. WGS was performed using Oxford Nanopore MinION (Rapid Barcoding Kit 24 V14 (SQK-RBK114.24). Data were processed using Galaxy Australia: Porechop for trimming, Flye for de novo assembly, and Abricate (Virulence Factor Database, ResFinder, and PlasmidFinder). Results The presence of blaCTX-M-65, amongst other resistance determinants conferring resistance to β-lactams, macrolides, aminoglycosides, tetracycline, sulfonamide, phenicol and fosfomycin were identified (Figure 1). Analyses of the genome indicated that the resistance were located on a 322518 bp plasmid that showed 99 % sequence similarity to an IncFIB plasmid (CP016409) (Figure 2). Clonality analysis showed that 100% isolates were belong to clone ST32 and all harbored the IncFIB plasmid. Furthermore, this plasmid contained genes associated with virulence, such as ybt (iron uptake), fae (fimbriae) which enhance the colonization capability and fitness of the bacterium. Conclusion The emergence of the multidrug-resistant (MDR) ESBL-producing S. enterica serovar Infantis has been linked to the presence of a unique pESI or pESI-like megaplasmid that enhances bacterial adaptation. The presence of pESI-like plasmids has demonstrated the emergence of a stable, resistant ST32 clone that has been circulating in the Ecuadorian population for some time, probably since 2014 (first reports). Disclosures All Authors: No reported disclosures