CDC’s Role in Tracking Resistance

NARMS Surveillance and Laboratory Testing

CDC, through NARMS, tracks antibiotic resistance and studies patterns of emerging resistance in select bacteria transmitted commonly through food. Surveillance helps identify patterns of emerging resistance that can guide public health prevention and policy efforts to protect people from resistant infections. This information is used by a variety of stakeholders, including federal regulatory agencies, policymakers, consumer advocacy groups, industry, and the public.

National surveillance for NARMS is in all 50 states; several large metropolitan areas participate independently (New York City, Los Angeles, Houston, and Washington, D.C.).

Laboratory Testing and Isolate Submissions

The CDC NARMS laboratory conducts antibiotic susceptibility testing on isolates from sporadic cases and outbreaks of illness. The laboratory also confirms and studies bacteria that have new antibiotic resistance patterns and performs research to understand the genetic mechanisms of resistance and how they are spread.

Routine Surveillance

Public health laboratories submit every 20th non-typhoidal Salmonella, Shigella, and Escherichia coli O157 isolate received at their laboratories to CDC NARMS for antibiotic susceptibility testing. They also submit every Salmonella serotype Typhi, serotype Paratyphi A, serotype Paratyphi C, and Vibrio (other than V. cholerae) isolate received at their laboratories.

Public health laboratories of the 10 state health departments that participate in CDC’s Foodborne Diseases Active Surveillance Network (FoodNet) also forward a sample of Campylobacter isolates to CDC for susceptibility testing. The FoodNet sites are Connecticut, Georgia, Maryland, Minnesota, New Mexico, Oregon, Tennessee, and selected counties in California, Colorado, and New York.

Antibiotic susceptibility testing information for pathogens
Pathogen tested Year testing began Current sampling scheme
Salmonella, non-Typhi1 1996 1 in 20
E. coli O157 1996 1 in 20
Shigella 1999 1 in 20
Campylobacter 1997 varies
Salmonella Typhi 1999 all
Salmonella Paratyphi A and C1 2008 all
Vibrio species other than V. cholerae 2009 all

1 From 1996–2007, Salmonella Paratyphi A, B, and C were included in the 1:20 sampling scheme for non-Typhi Salmonella. Since January 2008, sites were asked to submit all Paratyphi A and C isolates to NARMS. Salmonella Paratyphi B isolates continue to be included in the 1 in 20 sampling scheme for non-Typhi Salmonella.

Outbreak Investigations

CDC NARMS tests bacteria from outbreaks for antibiotic resistance. Resistance patterns and mechanisms can help investigators identify the source of an outbreak or provide clues about the source of the outbreak. Investigations of outbreaks of resistant Salmonella traced to food-producing animals show how animal and human health are linked.