What are NARMS Interim Data Updates?
NARMS interim data updates provide a summary of recent unusual or concerning antimicrobial resistance findings in enteric bacteria found through surveillance of retail meats. These updates are based upon using whole-genome sequence (WGS) analysis to screen for bacterial genes associated with resistance to one or more medically important antibiotics. Findings that would lead to a data update include but are not limited to
- Resistance to antimicrobials typically used to treat infections in humans (e.g., ceftriaxone and ciprofloxacin for treatment of severe Salmonella infections),
- Resistance to antimicrobials used as last-resort treatments (e.g., colistin), and
- Emergence of extensively drug-resistant clones.
NARMS interim data updates do not serve as notice of product recalls, alerts, or outbreaks of foodborne illness. Information about these events can be found at
NARMS Retail Meat Testing Interim Data Update: Multidrug-Resistant (MDR) Salmonella I 4,,12:i:-
In November of 2019, NARMS collected a retail pork sample that yielded a Salmonella serotype I 4,,12:i:- isolate (19MN11PC02) that is resistant to 10 out of 14 antibiotics on the NARMS Salmonella panel (see Table). Further genetic characterization of this isolate revealed a plasmid carrying both cephalosporin and fluoroquinolone resistance genes which is uncommon in Salmonella in the United States. To our knowledge, this is the first time this combination of resistance genes has been found in NARMS retail meat testing and raises concern since ceftriaxone (a cephalosporin) and ciprofloxacin (a fluoroquinolone) are critical drugs to treat severe Salmonella infections (CDC, Antibiotic Resistance Threats in the United States, 2019).
MDR profile of the NARMS isolate 19MN11PC02
|Aminoglycosides||Streptomycin||X||aadA1, aph(3')-Ia, aph(3'')-Ib, aph(6)-Id|
|Beta-lactam combination agents||Amoxicillin-Clavulanic Acid|
|Folate pathway antagonists||Sulfisoxazole||X||sul2|
|Folate pathway antagonists||Trimethoprim-Sulfamethoxazole||X||dfrA14|
|Penicillins||Ampicillin||X||blaCTX-M-15, blaOXA-1, blaTEM-1|
Organism: Salmonella I 4,,12:i:-
Source: Retail pork chop
Date collected: November 2019
Additional information on genetically similar Salmonella I 4,,12:i:- from pork and human clinical specimens can be found at NCBI’s Pathogen Detection Portal. At this time, the resistance pattern in Salmonella I 4,,12:i:-reported here is considered a rare finding in the United States.
Over the past decade, Salmonella I 4,,12:i:- has emerged as a major public health threat in Europe and the United States. In 2019, it ranked fifth among laboratory diagnosed nontyphoidal Salmonella infections in the United States (CDC).
FDA is performing additional genomic testing to better understand the origins of genes that caused the extensive resistance profile in 19MN11PC02 and other related I 4,,12:i:- isolates.
This notification is to inform stakeholders of this novel finding. While this rare finding by itself does not signify elevated risk, the public is advised to continue practicing safe handling of raw meats, as recommended by the USDA, and proper hygiene around animals as recommended by the CDC.