Characterization of a Multidrug-Resistant Salmonella Enteritidis Clinical Strain Carrying a Novel Hybrid Plasmid

A Salmonella Enteritidis clinical strain SAL045 isolated from an infant patient in China was subjected to whole genome sequencing. Strain SAL045 is resistant to 12 antibiotics tested including ampicillin and polymyxin E. A novel hybrid plasmid pS045A harboring 22 antibiotic resistance genes and 10 virulence genes was characterized. There were no sequences in the NCBI nucleotide database that completely covered the pS045A sequence. Sequence analysis indicated that pS045A was formed by IS26-mediated recombination of two plasmids. Plasmid pS045A was transferred to E. coli EC600 recipient strain at a frequency of 1.76 × 10^-6 per donor cell. Plasmid pS045A is a novel conjugative plasmid and might cause dissemination of drug-resistance and virulence genes within enterobacterial species.