J Glob Antimicrob Resist 2025 Jul 10; doi: 10.1016/j.jgar.2025.07.007.

Salmonella Minnesota sequence type 548 harboring a type 2 IncC megaplasmid of antimicrobial resistance and virulence (pESM) infecting a companion animal.

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OBJECTIVES: This study reports the identification and genomic characteristics of Salmonella strains isolated from a blood sample of a 9-year-old male Persian cat with a systemic infection (strain M885) and from a pleural effusion sample of a 9-year-old male Bulldog (strain T886) in Brazil. METHODS: Genomic DNA was sequenced using the Illumina NextSeq platform, de novo assembled by SPAdes v.3.15.2, and annotated by RAST server. Serovars, sequence types (ST), antimicrobial resistance genes, plasmid replicons, Salmonella pathogenicity islands, and single nucleotide polymorphisms (SNP) analysis were accomplished by bioinformatic tools. RESULTS: Strains M885 and T886 belonged to the serovars Sandiego (ST126) and Minnesota (ST548), respectively. Strain T886 carried blaCMY-2 and qnrB19 onto IncC2 and Col(pHAD28) plasmids, respectively. The blaCMY-2-bearing IncC2 plasmid also harbored mercury tolerance genes and the yersiniabactin virulence gene cluster, being classified as a type 2 IncC megaplasmid of antimicrobial resistance and virulence (pESM, plasmid for emergent S. Minnesota). SNP-based analysis revealed clonal relatedness between T886 strain with a CMY-2-producing S. Minnesota ST548 previously isolated from chicken sausage in Brazil, supporting a common ancestral origin. CONCLUSIONS: This study underscores the importance of monitoring S. enterica as the causative agent of extra-intestinal infections in small animal medicine. Therefore, the transmission dynamics and effective strategies for managing infections produced by multidrug-resistant clones adapted to the human-animal-environmental interface warrant further investigation.

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