Comparative Analysis of Extended-Spectrum-β-Lactamase CTX-M-65-Producing Salmonella enterica Serovar Infantis Isolates from Humans, Food Animals, and Retail Chickens in the United States

We sequenced the genomes of 10Salmonella enterica serovar Infantis isolates containingbla CTX-M-65 obtained from chicken, cattle, and human sources collected between 2012 and 2015 in the United States through routine National Antimicrobial Resistance Monitoring System (NARMS) surveillance and product sampling programs. We also completely assembled the plasmids from four of the isolates. All isolates had a D87Y mutation in thegyrA gene and harbored between 7 and 10 resistance genes [aph(4)-Ia ,aac(3)-IVa ,aph(3 ′)-Ic ,bla CTX-M-65 ,fosA3 ,floR ,dfrA14 ,sul1 ,tetA ,aadA1 ] located in two distinct sites of a megaplasmid (∼316 to 323 kb) similar to that described in abla CTX-M-65 -positiveS . Infantis isolate from a patient in Italy. High-quality single nucleotide polymorphism (hqSNP) analysis revealed that all U.S. isolates were closely related, separated by only 1 to 38 pairwise high-quality SNPs, indicating a high likelihood that strains from humans, chickens, and cattle recently evolved from a common ancestor. The U.S. isolates were genetically similar to thebla CTX-M-65 -positiveS . Infantis isolate from Italy, with a separation of 34 to 47 SNPs. This is the first report of thebla CTX-M-65 gene and the pESI (plasmid for emergingS . Infantis)-like megaplasmid fromS . Infantis in the United States, and it illustrates the importance of applying a global One Health human and animal perspective to combat antimicrobial resistance.