Characterization of Extended-Spectrum β-Lactamase (TEM-52)-Producing Strains of Salmonella enterica Serovar Typhimurium with Diverse Resistance Phenotypes

Two Salmonella enterica serovar Typhimurium strains from different clonal origins, both producing an extended-spectrum β-lactamase (TEM-52), were isolated from a patient. This enzyme was encoded on a single plasmid and was found at very low levels in one strain, while being encoded on multiple plasmids and in multiple different EcoRI fragments in the other strain.