Escherichia coli in Brazilian Poultry Fecal Samples: Co-Carriage of Fosfomycin and ESBL Resistance

<b>Background/Objectives</b>: Fosfomycin, a critically important antibiotic, is widely used to treat urinary tract infections (UTIs) caused by multidrug-resistant (MDR) <i>Escherichia coli</i>, particularly those producing extended-spectrum β-lactamases (ESBLs). However, its increasing use in livestock has raised concerns about resistance development and global dissemination. This study investigated fosfomycin resistance in <i>E. coli</i> isolates from 400 fecal samples collected at Brazilian broiler farms. <b>Methods</b>: The samples were tested for their minimum inhibitory concentration (MIC), screened with PCR for specific resistance genes, and selected isolated were whole genome sequenced. <b>Results</b>: Phenotypic resistance to fosfomycin was detected in 19% (75/400) of the isolates, while the <i>fosA3</i> gene, encoding enzymatic resistance, was identified in 4% (16/400) via PCR screening. Long-read sequencing of seven <i>fosA3</i>-positive isolates revealed the presence of <i>fosA3</i> on IncFII and IncX plasmids, often co-located with <i>bla</i>_CTX-M-55 within a conserved <i>IS</i>26-flanked transposon. Comparative genomic analysis of 133,541 global <i>E. coli</i> genomes from EnteroBase showed that 35% harbored similar transposon structures, with 2% carrying <i>fosA3</i>. These <i>fosA3</i>-positive isolates were significantly associated with South America and exhibited high co-carriage of ESBL genes, particularly in environmental and poultry-associated isolates. Phylogenetic analysis demonstrated no clustering by host or geographic origin, highlighting the global dissemination of these resistance determinants. <b>Conclusions</b>: Our findings emphasize the role of poultry production in the spread of fosfomycin and ESBL resistance, driven by transmissible plasmids and co-selection with third-generation cephalosporins. Improved antimicrobial stewardship, surveillance programs, and alternative management strategies are urgently needed to mitigate the dissemination of resistance and preserve fosfomycin's efficacy in human medicine.