NARMS Read Me First

by CDC Resources Editor AL last updated May 25, 2023 03:01 PM


The National Antimicrobial Resistance Monitoring System for Enteric Bacteria (NARMS) tracks antimicrobial resistance in foodborne and other enteric bacteria. NARMS is an interagency partnership among the Centers for Disease Control and Prevention (CDC), the US Food and Drug Administration (FDA), the US Department of Agriculture (USDA), and state and local health departments. The NARMS program at CDC (CDC-NARMS) helps protect public health by providing information about resistance in enteric bacteria from people, the ways in which resistance is spread, and how resistant infections differ from susceptible infections. NARMS surveillance of human bacterial isolates began in fourteen sites in 1996 and became nationwide for most pathogens it tracks in 2003. Public health laboratories submit bacterial isolates from clinical specimens to CDC-NARMS for antimicrobial susceptibility testing.


Antimicrobial resistance data on isolates from people are available via NARMS Now: Human Data, an interactive web tool.  Aggregate data from all states are included in the total counts and percentages displayed in tables, graphs, and maps; antimicrobial resistance data about isolates are available for most states. Data are refreshed daily and whenever criteria for interpretation of data are updated. (When standards-setting organizations update interpretive criteria, isolates might be re-classified as susceptible, intermediate, or resistant.) The Sanford Guide created antibiograms by using years of surveillance data from NARMS Now: Human Data, beginning with 2018.

Surveillance Isolate Submission and Testing

CDC-NARMS tests enteric bacterial isolates for antimicrobial susceptibility. The antimicrobial agents and drug classes tested vary by pathogen. Most state public health laboratories require clinical laboratories to send them all Salmonella and Shigella isolates. Public health laboratories submit to CDC-NARMS every 20th nontyphoidal Salmonella and Shigella isolate and every isolate of Salmonella serotypes Typhi, Paratyphi A, and Paratyphi C. Public health laboratories from the 10 FoodNet sites submit a frequency-based sample of Campylobacter isolates. Click here for more details about the sampling methodology. CDC-NARMS determines minimum inhibitory concentrations (MICs) by broth microdilution using dried panels.

Interpretive Criteria

The Sanford Guide uses standards and guidelines provided by the Clinical and Laboratory Standards Institute (CLSI) to categorize MIC results as susceptible, intermediate, or resistant. The Sanford Guide’s antibiogram results for Campylobacter species may differ slightly from the values on the NARMS Now: Human Data platform because Sanford Guide uses CLSI criteria for interpretation of MIC results whereas CDC-NARMS uses epidemiological cutoff values established by the European Committee on Antimicrobial Susceptibility Testing. Click here for more information on the antimicrobial agents tested for each pathogen and the interpretive criteria used by CDC-NARMS.


CDC provides data via NARMS Now: Human Data to raise awareness about antimicrobial resistance trends in the United States. However, it is important to understand these data are not intended or implied to be substitutes for professional medical advice, diagnosis, testing, or treatment. The antimicrobial agent recommendations shown on Sanford Guide do not signify CDC endorsement. Additionally, please note that the color scheme in the CDC antibiogram denotes the percent susceptibility of each pathogen-antimicrobial agent combination: Blue (95–100% susceptible); green (81–94% susceptible); yellow (51–80% susceptible); red (≤50% susceptible). These colors do not indicate the appropriateness of each agent for treatment as described in the “Legend” feature.

NARMS Now: Human Data

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