In recent years, antimicrobial resistance (AMR) among Salmonella serotypes of public health concern worsened regarding critical antibiotics, according to a recent report published by the U.S. Department of Agriculture’s Food Safety and Inspection Service (USDA’s FSIS). The report highlights multi-year trends for Salmonella AMR from data collected by the National Antimicrobial Resistance Monitoring System (NARMS) during 2014–2019.
NARMS is a national public health system that tests bacteria from human and animal samples to monitor select pathogens’ antimicrobial resistance (AMR) to drugs used in human and veterinary medicine. NARMS is conducted in cooperation with the U.S. Centers for Disease Control and Prevention (CDC) and the U.S. Food and Drug Administration (FDA). FSIS testing focuses on bacteria from animal cecal contents, as well as regulated food products.
FSIS found that the proportion of pan-susceptible Salmonella differed among slaughter classes and sample sources. For cattle, 83 percent of cecal samples and 71 percent of product samples were pan-susceptible; for swine, 65 percent and 64 percent, respectively; for chicken, 35 percent and 43 percent, respectively; and for turkey, 34 percent and 32 percent, respectively. Pan-susceptibility indicates that a pathogen was not resistant to any of the tested drugs.
The top Salmonella serotypes found in each slaughter class were S. Kentucky in chicken, S. Reading in turkey, S. Montevideo in cattle, and S. Anatum in swine. S. Infantis showed an increasing trend in chicken, and emerged as one of the top serotypes in both cecal and product samples. Additionally, S. Infantis from both cecal and product samples showed increased multidrug resistance.
FSIS also found that Salmonella isolates from chicken cecal and product samples show a significant increase in resistance to the critically important antimicrobial drugs ciprofloxacin, ceftriaxone, and trimethoprim-sulfamethoxazole. Moreover, Salmonella isolates from product samples from cattle and swine showed increased resistance to cephalosporin.