Overview of the Antimicrobial Resistance of Salmonella Recovered from U.S. Poultry Processing Plants

Abstract

The objectives of this study were to analyze the results of antimicrobial susceptibility testing on Salmonella isolated from poultry carcass and parts rinsates using a scoring system for antimicrobial resistance (AMR) and to deter-mine whether the resistance of Salmonella to selected antimicrobials critically or highly important to human medicine changed from 2017 to 2019. Samples were collected from 26 plants in the United States, analyzed for the presence of Salmonella, and tested for susceptibility to 12 antimicrobials (n=734 for 8 antimicrobials; n=597 for 4 antimicrobials). The multidrug resistance (MDR) scores and AMR scores remained the same over time (P>0.05); however, MDR and AMR differed (P<0.0001) by serogroup and serogroup-by-year interactions. Most notably, MDR—and AMR for 7 out of the 12 antimicrobials—was greater (P<0.05) in serogroup C1 than other serogroups and/or lower (P<0.05) in serogroup D1 than other serogroups. The effect year-by-serogroup was also significant for MDR (P<0.0001) and—for 8 out of the 12 antimicrobials—AMR (P<0.05); differences (P<0.05) across years were identified in serogroup C1, B, and C2 but were highly variable. Resistance to ciprofloxacin and ceftriaxone,“highest priority critically important antimicrobials”to human medicine, were not different (P>0.05) across years, but there were significant (P<0.05) serogroup and serogroup-by-year effects for ceftriaxone resistance. Interestingly, gentamicin resistance across years differed (P<0.05) in serogroup B and C. Overall, mean Salmonella MDR and AMR scores were stable from year to year, but shifts in AMR in Salmonella serogroups across years were identified, emphasizing the need to continue monitoring AMR in Salmonella isolated from poultry products in the interest of food safety and human health.