Highlights
- REPJJP01 is a persistent strain of multidrug-resistant Salmonella Newport bacteria that has caused illnesses and outbreaks in the United States.
- Most outbreaks caused by this strain have been linked to travel to Mexico, beef products purchased in the United States, and cheese purchased in Mexico.
- REPJJP01 infections may not be treatable with some antibiotics normally used to treat serious Salmonella because they are resistant to these antibiotics.
- Additional research could help determine where this strain is coming from and how to prevent future illnesses.
At a glance
First detection
Outbreaks investigated
- International travel to Mexico: 6 outbreaks
- Beef obtained in the United States: 5 outbreaks (1 confirmed, 4 suspected)
- Cheese obtained in Mexico: 1 outbreak (suspected)
*Most isolates were multidrug resistant, but not all.
Key findings
REPJJP01 is a persistent, often multidrug-resistant strain of Salmonella Newport bacteria that has caused illnesses and outbreaks in the United States and in other countries.
Illness caused by this strain was first reported in late 2015.
Multiple sources
REPJJP01 has spread to people through international travel, beef products from the United States, and cheese obtained in Mexico.
Genetically diverse
This strain of Salmonella Newport is relatively diverse genetically based on results from whole genome sequencing (WGS).
Genetic diversity can increase over time as strains pass among human hosts, animal hosts, and environmental settings, each with different selective pressures. Understanding this genetic diversity helps public health officials identify related illnesses and better understand how these strains continue to spread and persist over time.
What the data show
Illnesses and outbreaks
Lab-confirmed REPJJP01 infections
Among 2,160 people who provided race and ethnicity
- 58% were Hispanic/Latino
- 38% were non-Hispanic/Latino White
- 5% were non-Hispanic/Latino and another race
Among 2,262 people with available travel information
- Almost half (47%) reported traveling to Mexico
- 1% reported traveling to countries other than Mexico, including Brazil, Colombia, Costa Rica, the Dominican Republic, or Guatemala
- 52% reported no international travel before their illness began
Outbreaks and other investigations
Although most enteric illnesses—including those caused by REPJJP01—are not part of an outbreak, investigation of outbreaks provides information that increases our understanding of germs, sources, settings, and factors that contribute to illness.
Starting in 2016, CDC and local, state, and federal health and regulatory partners have investigated several outbreaks of Salmonella Newport illnesses caused by the REPJJP01 strain.
Summary of selected multistate outbreaks
| Outbreak | Dates people got ill | Outbreak source |
Geographic location of outbreak source | Reported illnesses | Number of states with illnesses |
|---|---|---|---|---|---|
| A | August 2014–July 2017 | Unknown | Mexico and the United States | 53 | 17 |
| B | June 2018–March 2019 | Cheese obtained in Mexico, beef obtained in the United States (suspected), and unknown | Mexico and the United States | 255 | 32 |
| C | September 2021–January 2022 | Dried beef from Mexico and beef obtained in the United States (suspected) | Mexico and the United States | 72 | 6 |
| D | December 2021 | Beef obtained in the United States (suspected) | United States | 5 | 1 |
| E | August 2022 | Ill food handler (suspected) | United States | 7 | 1 |
| F | August–October 2022 | Ground beef obtained in the United States | United States | 22 | 6 |
| G | January–March 2023 | Unknown | Mexico | 24 | 17 |
| H | February–April 2023 | Unknown | Mexico | 23 | 17 |
| I | July–September 2023 | Unknown | Mexico | 18 | 11 |
| J | September 2023 | Ground beef obtained in the United States (suspected) | United States | 5 | 1 |
| K | September–October 2023 | Unknown | United States | 3 | 1 |
| L | February–July 2024 | Person-to-person transmission in a day care | United States | 4 | 1 |
| M | July 2024 | Unknown | Mexico | 10 | 8 |
| N | October–December 2024 | Unknown | Mexico | 13 | 13 |
Selected outbreak publications
- Outbreak B - Outbreak of Salmonella Newport infections with decreased susceptibility to azithromycin linked to beef obtained in the United States and soft cheese obtained in Mexico — United States, 2018–2019
- Outbreaks C and F - Strain of multidrug-resistant Salmonella Newport remains linked to travel to Mexico and U.S. beef products — United States, 2021–2022
- Outbreak J – Foodborne outbreak of Salmonella: An uninvited wedding reception guest
Timeline
Map
Laboratory data
Whole genome sequencing analysis
Bacteria in this strain are within 24 allele differences of one another by core genome multilocus sequence typing. This is more diverse than typical multistate foodborne outbreaks, in which bacteria generally are within 10 allele differences of one another.
Genetic diversity can increase over time as strains pass among human hosts, animal hosts, and environmental settings, each with different selective pressures. Understanding this genetic diversity helps public health officials identify related illnesses and better understand how these strains continue to spread and persist over time.
Isolates from food, animal, and environmental samples
Information from 98 REPJJP01 isolates from animals and food products has been reported to PulseNet.
Most isolates were obtained from beef products and cecal samples from the large intestines of cattle and were detected as part of routine surveillance performed by the USDA Food Safety and Inspection Service (USDA-FSIS) and the USDA Agricultural Marketing Service (USDA-AMS), or as part of sampling performed by the National Antimicrobial Resistance Monitoring System (NARMS).
One isolate from a papaya and six isolates from pet treats were detected as part of routine surveillance performed by the U.S. Food & Drug Administration (FDA).
| Year | Number of isolates |
Isolate source | Source type | Geographic location of source | Reason collected |
|---|---|---|---|---|---|
| 2016 | 1 | Food | Beef | Texas | Routine sampling by USDA-FSIS |
| 2018 | 1 | Cecal content | Beef | Texas | Routine sampling by USDA-FSIS-NARMS |
| 2018 | 1 | Food | Beef | Texas | Routine sampling by USDA-AMS |
| 2018 | 1 | Food | Queso Fresco and Oaxaca Cheese | California | Outbreak B |
| 2019 | 1 | Cecal content | Beef | Texas | Routine sampling by USDA-FSIS-NARMS |
| 2019 | 6 | Food | Beef | Texas (5 isolates; 1 import sample from Mexico) & Utah (1 isolate) | Routine sampling by USDA-FSIS |
| 2019 | 2 | Food | Beef | California | Routine sampling by USDA-AMS |
| 2019 | 1 | Food | Papaya | California | Routine sampling by FDA |
| 2020 | 2 | Cecal content | Beef | Nebraska & Texas (1 isolate each) | Routine sampling by USDA-FSIS-NARMS |
| 2020 | 1 | Mesenteric lymph node | Beef | Arizona | Routine sampling by USDA-FSIS-NARMS Expansion Sampling |
| 2020 | 2 | Food | Beef | Florida (1 isolate) & Texas (1 isolate; import sample from Mexico) | Routine sampling by USDA-FSIS |
| 2020 | 4 | Food | Beef | Texas (4 isolates) | Routine sampling by USDA-AMS |
| 2020 | 3 | Pet food | Bully Stick (Beef) | Colorado (import sample from Mexico) | Routine sampling by FDA |
| 2021 | 4 | Cecal content | Beef | Kansas, Maryland (1 isolate each), and Texas (2 isolates) | Routine sampling by USDA-FSIS-NARMS |
| 2021 | 1 | Mesenteric lymph node | Beef | Texas | Routine sampling by USDA-FSIS-NARMS |
| 2021 | 6 | Food | Beef | Illinois, Kansas, Missouri, Tennessee, Texas, & Wisconsin (1 isolate each) | Routine sampling by USDA-FSIS |
| 2021 | 2 | Food | Beef | Texas | Routine sampling by USDA-AMS |
| 2021 | 1 | Cecal content | Sheep | California | Routine sampling by USDA-FSIS-NARMS |
| 2022 | 2 | Food | Beef | Michigan | Outbreak F |
| 2022 | 1 | Cecal content | Beef | Texas | Routine sampling by USDA-FSIS-NARMS |
| 2022 | 8 | Food | Beef | Alabama, Florida, Georgia, Illinois, Kansas, Washington (1 isolate each), and Texas (2 isolates) | Routine sampling by USDA-FSIS |
| 2022 | 1 | Food | Beef | Illinois | Routine sampling by Illinois Department of Agriculture |
| 2023 | 4 | Cecal content | Beef | Colorado, Texas (1 isolate each), and Kansas (2 isolates) | Routine sampling by USDA-FSIS-NARMS |
| 2023 | 6 | Food | Beef | California (2 isolates; 1 from import sample from Mexico), North Carolina (1 isolate), & Texas (3 isolates) | Routine sampling by USDA-FSIS |
| 2023 | 11 | Food | Beef | Nebraska (1 isolate) & Texas (10 isolates) | Routine sampling by USDA-AMS |
| 2024 | 6 | Cecal content | Beef | Kansas, Nebraska (1 isolate each), and Texas (4 isolates) | Routine sampling by USDA-FSIS-NARMS |
| 2024 | 6 | Food | Beef | California, Illinois, Kansas, Minnesota (1 isolate each), and Texas (2 isolates) | Routine sampling by USDA-FSIS |
| 2024 | 1 | Food | Pork | Kentucky | Routine sampling by USDA-FSIS |
| 2024 | 3 | Pet food | Rawhide braid (Beef) | Import from Mexico | Routine sampling by FDA |
| 2025 | 4 | Food | Beef | Import from Mexico, Illinois, Kansas, Nebraska (1 isolate each) | Routine sampling by USDA-FSIS |
| 2025 | 3 | Food | Beef | Texas (1 isolate) & Washington (2 isolates) | Routine sampling by USDA-AMS |
| 2026 | 1 | Food | Beef | Texas | Routine sampling by USDA-FSIS |
| 2026 | 1 | Cecal content | Beef | Texas | Routine sampling by USDA-FSIS-NARMS |
Genomic information
The National Center for Biotechnology Information (NCBI) advances science and health by providing access to biomedical and genomic information.
Antimicrobial resistance
The National Antimicrobial Resistance Monitoring System (NARMS) is a national public health surveillance system that tracks antimicrobial resistance for certain intestinal bacteria from ill people (CDC), food animals (USDA), and retail meats (FDA) in the United States. The NARMS program helps protect public health by providing information about emerging antimicrobial resistance, the ways in which resistance spreads, and how resistant infections differ from susceptible infections.
Bacteria from most ill people's samples showed resistance to antibiotics, including several recommended for first-line or alternative treatment: ampicillin, azithromycin, ciprofloxacin, and trimethoprim-sulfamethoxazole.
Most people with Salmonella illness recover without antibiotics. However, if antibiotics are needed, some REPJJP01 illnesses may not be treatable with commonly recommended antibiotics and may require a different antibiotic choice. When possible, healthcare providers should use antimicrobial susceptibility testing results to guide treatment.
Collaborate with CDC
Interested in collaborating on a project related to this strain? Contact CDC at REPStrains@cdc.gov.
About the data
Lab-confirmed cases are only a small part of the actual number of illnesses. Most people do not seek medical care and even fewer submit a stool specimen.
PulseNet transitioned to using WGS as the standard subtyping method for Salmonella in July 2019. Before then, not all Salmonella isolates reported to PulseNet had WGS data available. Isolates are identified as part of this strain based on WGS. As a result, the number of people with lab-confirmed illness caused by this strain before 2019 may be underrepresented.
Outbreak dates are based on reported or estimated illness onset dates.
Confirmed sources were identified by epidemiology plus traceback or laboratory data. Suspected sources were identified by epidemiology only. More information about determining outbreak sources is available in the latest summary of possible multistate enteric disease outbreaks.
The geographic location of a confirmed outbreak source may not always be known. This can happen when:
- a product (e.g., ground meat) sold from or mixed with other products from multiple suppliers is confirmed as the source, but evidence cannot implicate a specific supplier; or
- evidence confirms an outbreak source but traceback cannot pinpoint the exact geographic location of the source. In these cases, geographic location of an outbreak source represents where patients were likely infected.
The number of illnesses and states listed per outbreak in this table may differ from other reports (e.g., publications). This is because this table only includes illnesses with WGS data that meet the allele range for this REP strain (see Laboratory data section).
Selected publications on Salmonella Newport are for reference; other publications regarding this strain are available.
Includes 3,631 human illnesses for which information was reported as of March 31, 2026. Some illness onset dates have been estimated from other reported information.
The "by year" view of the timeline labels each bar as "January" because of a limitation in the data visualization. Switch to the "by month" view to see a more detailed breakdown of when people became ill.
Includes 3,631 human illnesses for which information was reported as of March 31, 2026.
Resistance information was available for 3,616 cases. Resistance was determined based on the results of antimicrobial susceptibility testing when available (190 isolates). Otherwise, resistance was predicted based on WGS (3,426 isolates).
Interpretive criteria for azithromycin resistance have not been established for Salmonella serotypes other than serotype Typhi. Therefore, the presence of resistance determinants for azithromycin should not be used to predict clinical efficacy.
Ciprofloxacin data includes isolates with an intermediate interpretation on antimicrobial susceptibility testing or a single quinolone resistance mechanism (a single mechanism is typically associated with intermediate interpretation in Salmonella).
Resistance determination for kanamycin, ceftiofur, and fosfomycin was based only on predicted resistance from whole genome sequencing (3,615 isolates).
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