Antimicrobial Resistance Monitoring: Expanding FSIS Surveillance 

The National Antimicrobial Resistance Monitoring System (NARMS) is a surveillance program 

run by the U.S. Department of Agriculture’s Food Safety and Inspection Service (FSIS) and public 

health partners. NARMS provides information about emerging bacterial resistance. 

In 2020, we expanded NARMS sampling to include mesenteric lymph nodes (MLN) in cattle and 

intestinal (also called cecal) sampling in sheep, goat, lamb and veal. We also added other 

bacterial analyses to the existing Salmonella testing for Siluriformes fish (types of catfish). 

We started sampling cattle MLN to see if there were any Salmonella serotypes with 

antimicrobial resistance (AMR) that were not seen in the ongoing NARMS cattle cecal sampling. 

To do this, FSIS public health veterinarians collected cecal content and MLN samples from the 

same animal (i.e., paired samples) and submitted these to the FSIS labs for testing. Preliminary 

findings indicate that 14.65% (63/430) MLN were positive for Salmonella. Of the 63 Salmonella 

recovered from MLN, 11 matched the serotype of the paired cecal sample and four pairs were 

closely related genetically, as determined by whole genome sequencing technology. Only three 

MLN Salmonella isolates (out of 63) exhibited AMR and their profiles were identified as 

multidrug resistant (MDR) (resistant to 3 or more types of antimicrobial drugs). The types of 

AMR seen in MLN Salmonella serotypes were no different from those found in cattle cecal 

contents, so we decided to end MLN sampling in October of this year. 

When we tested Salmonella in Siluriformes fish and the cecal contents of minor species and 

veal, we found that a majority (over 77%) of the Salmonella were not resistant to 

antimicrobials. As expected, in the NARMS expansion samples, less than 10% of Salmonella 

found were MDR. This study is ongoing, and we will conduct further AMR analyses for 

Salmonella as well as Campylobacter, E. coli and Enterococcus found in the samples we collect. 

Antimicrobial resistance data from ceca provide a snapshot of the preslaughter exposure of the 

animals to factors that may trigger or spread AMR. FSIS ensures food safety and safeguards 

public health through its stringent oversight of inspection procedures related to animal 

slaughter and processing. This includes slaughter establishments’ compliance with the sanitary 

dressing procedures. During sanitary dressing, the animal’s digestive tract (including cecal 

contents) is removed entirely and antimicrobials may be applied to address incidental 

contamination on carcasses. There is a zero-tolerance standard for fecal contamination on 

carcasses. As a result, the AMR findings from cecal content samples do not reflect imminent 

and direct consumer exposure. Instead, the findings inform the NARMS surveillance about 

preslaughter changes in AMR trends, and the development and/or spread of novel AMR as seen 

via the cecal content bacteria. Details on the scope of FSIS NARMS testing and more analyses of 

our NARMS expansion work can be found on FSIS's NARMS Webpage. 

Uday Dessai, Gamola Fortenberry, Catherine Rockwell, Leslie Manis, Mustafa Simmons, Glenn 

Tillman, Spencer Pretecrum, Sheryl Shaw, USDA Food Safety and Inspection Service