Whole-genome sequencing of <i>Salmonella</i> serovars isolated from diarrheic and non-diarrheic foals

<i>Salmonella</i> spp. are important pathogens of foals, causing clinical enterocolitis and sepsis. We characterized the resistance, virulence, and stress response genes in <i>Salmonella</i> isolates from foals with or without diarrhea. <i>Salmonella</i> isolates (<i>n</i> = 23) recovered from fecal samples of 16 diarrheic and 7 non-diarrheic <1-y-old foals were subjected to whole-genome sequencing. The most common serovars detected in diarrheic foals were <i>S. enterica</i> subsp. <i>enterica</i> serovars Infantis and Minnesota. Multidrug resistance was observed in 9 of 23 isolates, with 8 of the 9 from diarrheic foals. All of the isolates contained at least 2 resistance genes, with most of the genes related to the multidrug efflux pump complex. Among the 9 isolates shown to be resistant to β-lactam antimicrobials, at least one antimicrobial resistance gene (ARG) related to the inactivation of these antimicrobials was observed (<i>bla</i>_TEM-1, <i>bla</i>_CMY-2, <i>bla</i>_CTX-M-8). Among the 7 isolates resistant to the quinolone class, 3 contained ARGs (<i>qnrB19</i>, <i>qnrB6</i>). The occurrence of multidrug-resistant isolates, particularly among foals with diarrhea, and the zoonotic potential of <i>Salmonella</i> species, highlight the importance of implementing biosecurity measures on the studied farms.