Highlights
- REPJFX01 is a persistent strain of multidrug-resistant Salmonella Infantis bacteria that has caused illnesses and outbreaks in the United States and globally.
- This strain has spread to people through contaminated chicken in the United States and through exposures during international travel.
- REPJFX01 infections may not be treatable with some antibiotics normally used to treat serious Salmonella infections.
At a glance
- Raw chicken products: 1 outbreak
- Mechanically separated chicken (suspected): 2 outbreaks
- Cabbage salsa (suspected; cross-contamination): 1 outbreak
- Person-to-person contact: 2 outbreaks
Key findings
REPJFX01 is a persistent, multidrug-resistant strain of Salmonella Infantis bacteria that has caused illnesses and outbreaks in the United States and globally.
Illness caused by this strain was first reported to PulseNet in 2012. Illnesses caused by this strain occur year-round but are most common in July and August.
This strain of Salmonella Infantis is relatively diverse genetically. Bacteria in the strain are within 82 allele differences of one another by. This is more genetically diverse than typical multistate foodborne outbreaks, in which bacteria generally fall within 10 allele differences of one another.
What the data show
Illnesses and outbreaks data
Lab-confirmed REPJFX01 infections
Among a subset of 471 patients
- 30% were hospitalized
- 6% were admitted to the intensive care unit
- 1% died
The median age of patients was 54 years (interquartile range, 27–70 years), and 63% were female.
The isolate source was stool in 66% and urine in 27% of cases.
Among a subset of 471 patients, 9% traveled internationally in the 7 days before their illness began.
Most traveled to the Dominican Republic (25%), Peru (19%), or Ecuador (11%).
Outbreaks and other investigations
Although most enteric illnesses—including those caused by REPJFX01—are not part of an outbreak, investigation of outbreaks provides information that increases our understanding of bacteria, sources, settings, and factors that contribute to illness. Moreover, lab-confirmed cases comprise only a small portion of the true number of illnesses that occur because most people do not seek medical care and even fewer submit a clinical (e.g., stool) specimen.
CDC and local, state, and federal health and regulatory partners have investigated several clusters of Salmonella Infantis illness as possible outbreaks caused by the REPJFX01 strain.
Summary of selected multistate outbreaks and other investigations
| Outbreak | Dates of illness onset |
Outbreak source |
WGS-linked Illnesses |
Number of states with WGS-linked Illnesses |
More information |
|---|---|---|---|---|---|
| Outbreak A | May 15– August 19, 2016 |
Mechanically separated chicken (suspected) |
3 | 1 | |
| Outbreak B | January 5– March 28, 2017 |
Unknown | 7 | 6 | |
| Outbreak C | February 9– July 23, 2017 |
Unknown | 39 | 22 | |
| Outbreak D | April 25– June 7, 2017 |
Unknown | 5 | 3 | |
| Outbreak E | December 1, 2017–January 2, 2018 | Person-to-person (child daycare) | 3 | 1 | |
| Outbreak F | March 1–15, 2018 | Unknown | 2 | 1 | |
| Outbreak G | June 23–September 14, 2018 | Unknown | 12 | 7 | |
| Outbreak H | July 28–October 10, 2018 | Unknown | 10 | 7 | |
| Outbreak I | April 5–September 28, 2019 | Person-to-person (long-term care facility) | 6 | 1 | |
| Outbreak J | October 10, 2018–January 27, 2019 | Raw chicken products | 113 | 31 | |
| Outbreak K | July 24–August 5, 2019 | Cabbage salsa (suspected) | 5 | 1 | Possible cross-contamination of restaurant item |
| Outbreak L | August 2–September 4, 2019 | Unknown | 1 | 1 | |
| Outbreak M | September 24–October 7, 2019 | Mechanically separated chicken (suspected) | 1 | 1 | |
| Outbreak N | February 25–March 10, 2020 | Restaurant, unknown vehicle | 8 | 1 | Multiple health code violations; one ill food handler |
Selected publications regarding REPJFX01 investigations
- (2021)
- (2020)
- (2018)
- (2018)
- (2017)
Timeline
People with Salmonella Infantis illnesses caused by the REPJFX01 strain, by month of isolate collection, 2012–2024
Map
Salmonella Infantis illnesses caused by the REPJFX01 strain, by state, 2012–2024
Laboratory data
Whole genome sequencing analysis
Bacteria in this strain are within 82 allele differences of one another by . This is more genetically diverse than typical multistate foodborne outbreaks, in which bacteria generally fall within 10 allele differences of one another. Increased diversity can occur over time as strains pass among human hosts, animal hosts, and environmental settings, each with different selective pressures.
Isolates from food, animal, and environmental samples
Information from more than 8,000 REPJFX01 isolates from non-human sources has been reported to PulseNet, with the earliest in 2014. Most isolates are from chicken samples collected by the , including 5,738 from FSIS sampling of food and food products and 586 from FSIS sampling of intestinal (cecal) content. Other non-human sources of bacteria sequences reported to PulseNet include
- Turkey (286 isolates)
- Pork or swine (60)
- Beef or cattle (51)
- Water (20); and
- Other food, animal, and environmental sources (55).
Although WGS data from samples have not always been submitted to PulseNet, more than 1,000 food and environmental isolates collected through FDA sampling programs are highly related to REPJFX01 isolates by WGS, including many samples from retail chicken products. More information about these isolates can be found through the or the platform.
Number of REPJFX01 isolates from non-human sources submitted to PulseNet, by month of sample collection, 2012–2024
Genomic information
The National Center for Biotechnology Information (NCBI) advances science and health by providing access to biomedical and genomic information.
Antimicrobial-resistant isolates
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), (USDA), and (FDA) in the United States. The NARMS program helps protect public health by providing information about emerging antimicrobial resistance, the ways in which resistance is spread, and how resistant infections differ from susceptible infections.
Bacteria from most ill people's samples showed resistance to multiple antibiotics, including several recommended for first-line or alternative treatment: ampicillin, ceftriaxone, ciprofloxacin, and trimethoprim-sulfamethoxazole.
Most people with Salmonella illness recover without antibiotics. However, if antibiotics are needed, some illnesses resulting from REPJFX01 may not be treatable with commonly recommended antibiotics and may require a different antibiotic choice. Results from antimicrobial susceptibility testing .
Percentage of human Salmonella REPJFX01 isolates that were antimicrobial resistant, by antibiotic, as of December 31, 2024 — NARMS
Collaborate with CDC
Interested in collaborating on a project related to this strain? Contact CDC at REPStrains@cdc.gov.
About the data
Information provided in the "Morbidity and mortality," "Antibiotic treatment," and "Travel" rows is based on data from a subset of 471 patients with records in the Foodborne Diseases Active Surveillance Network (FoodNet) during 2018–2023.
Outbreak dates are based on reported or estimated illness onset dates.
Confirmed sources were implicated by epidemiologic plus traceback or laboratory data. Suspected sources were implicated by epidemiologic data only. More information about determining outbreak sources available in the latest summary of possible multistate enteric disease outbreaks.
The number of illnesses and states listed per outbreak in this table may differ from other reports (e.g., publications). This is because the table only includes illnesses with whole genome sequencing (WGS) data that meet the allele range for this REP strain (see Genomic Information section).
Outbreak data were obtained from the System for Enteric Disease Response, Investigation, and Coordination (SEDRIC) and the National Outbreak Reporting System (NORS).
Selected publications on Salmonella Infantis are for reference; other publications regarding this strain are available.
Includes 3,904 human illnesses for which information was reported as of December 31, 2024.
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.
PulseNet transitioned to using whole genome sequencing (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.
Includes 3,904 human illnesses for which information was reported as of December 31, 2024. Illness year is based on the date of isolate collection.
Includes 8,367 non-human isolates for which information was reported as of December 31, 2024. Some collection dates have been estimated from other reported information.
Isolates sequenced by FSIS from non-chicken sources included
- 21 isolates from cecal contents (part of the animals' intestines)
- 1 isolate from a food animal, and
- 317 isolates from food, food products, and environmental sources.
Isolates sequenced by FSIS include isolates collected by the .
The exploratory testing was performed on (prior to evisceration and prior to application of all interventions).
The SNP (single nucleotide polymorphism) tree provided by NCBI's Pathogen Detection Pipeline in the link above may include isolates that are not considered part of this strain. The difference in allele vs. SNP thresholds occurs because NCBI's Pathogen Detection Pipeline uses an analysis pipeline different from the one used by PulseNet.
The link is provided to give context to the overall genetic relatedness of the strain reported on this page, as well as to provide links to raw sequence files. The SNP trees on NCBI's Pathogen Detection Pipeline are updated more frequently than this web page.
Resistance information was available for 3,866 cases. Resistance was determined based on the results of antimicrobial susceptibility testing when available (211 isolates). Otherwise, resistance was predicted based on whole genome sequencing (3,655 isolates).
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 was based only on predicted resistance from whole genome sequencing for hygromycin, tobramycin, trimethoprim, kanamycin, and fosfomycin.