Whole Genome Sequence Analysis of the First Reported Isolate of Salmonella Agona Carrying BlaCTX-M-55 Gene in Brazil

This study analyzes the genomic findings of the first report of Salmonella isolate carrying the bla gene, recovered from a bacteremic patient from Brazil. A bacterial isolate positive for the bla gene was submitted to antimicrobial susceptibility testing by disk diffusion and epsilometric test. Whole genome sequencing was performed using Illumina technology. Conjugation assay was performed; plasmid sizes determined by S1-PFGE and plasmid content were investigated by hybrid assembly after MinION long reads sequencing. Isolate 288_18 was identified as sequence type ST13, resistant to ampicillin, cefotaxime, ceftazidime, cefepime, ceftriaxone, and aztreonam. A transferable IncFII plasmid sized approximately 67 kb was found to carry the bla and bla in a module consisting of IS26-bla-WbuC-bla-IS26. In addition, an 117 kb IncI1plasmid was also identified in the 288_18 isolate, but without additional resistance genes. To the best of our knowledge, this is the first report of bla in Salmonella isolated from human infection in Brazil. The occurrence of bla in the IncFII epidemic plasmid in a relevant clinical human isolate of Salmonella Agona underscores the urgent need for enhanced and effective continuous surveillance for controlling its dissemination.