Highlights
- REPDBR01-1, REPDBR01-2, and REPDBR01-3 are persistent, extensively drug-resistant strains of Campylobacter jejuni bacteria (collectively referred to as “REPDBR01”).
- These strains have caused illnesses and outbreaks in the United States.
- REPDBR01 has spread to people through contact with dogs carrying these strains, especially puppies from pet stores.
- REPDBR01 infections may not be treatable with antibiotics commonly recommended for Campylobacter infection, limiting treatment options.
At a glance
REPDBR01-1
REPDBR01-2
REPDBR01-3
Key findings
REPDBR01-1, REPDBR01-2, and REPDBR01-3 are persistent, extensively drug-resistant strains of Campylobacter jejuni bacteria (collectively referred to as "REPDBR01") that have caused illnesses and outbreaks in the United States.
Illness caused by these strains was first reported in 2007.
Genetically diverse
These strains of Campylobacter jejuni are relatively diverse genetically based on results from whole genome sequencing.
Genetic diversity can increase over time as strains pass among human hosts, animal hosts, and environmental settings, each with different selective pressures.
What the data show
Illnesses and outbreaks data
Lab-confirmed REPDBR01 infections
Among 273 ill people who provided race and ethnicity:
- 87% were White non-Hispanic
- 7% were Hispanic/Latino
- 4% were Black non-Hispanic
- 2% were another non-Hispanic race
REPDBR01 has spread to people through contact with dogs carrying these strains, especially puppies (typically younger than 6 months). 96% percent of ill people reported contact with a dog before becoming ill. Among those with additional information:
- 73% reported contact with a pet store puppy
- 7% reported contact with a puppy from another setting, such as a shelter or breeder
Among those with contact with pet store puppies:
- 68% were pet store customers
- 27% were pet store employees
- 4% were pet store visitors
- 2% had contact with a pet store puppy purchased by someone else
Some of the associated puppies showed signs of illness, such as diarrhea. Some showed no signs of illness.
Outbreaks and other investigations
Although most enteric illnesses—including those caused by REPDBR01 strains—are not investigated as part of an outbreak, outbreak investigation provides information that increases our understanding of bacteria, sources, settings, and factors that contribute to illness.
CDC and local, state, and federal public health and regulatory partners have investigated three outbreaks of Campylobacter jejuni illnesses caused by REPDBR01 strains.
These strains have been identified in pet store puppies, but the factors that influence why some puppies carry these strains are not completely understood. Evidence collected during outbreak investigations indicate these strains are widespread in the dog breeding industry.
| Outbreak | Dates people became ill | Outbreak source | Reported illnesses | Number of states with illnesses | More information |
|---|---|---|---|---|---|
| A | January 12, 2016 – January 7, 2018 | Pet store puppies (confirmed) | 113 | 17 | CDC Investigation Notice |
| B | January 6, 2019 – January 2, 2021 | Pet store puppies (confirmed) | 56 | 17 | CDC Investigation Notice |
| C | May 19, 2024 – August 11, 2024 | Pet store puppies (confirmed) | 3 | 3 |
Selected publications regarding REPDBR01 investigations
- All REPDBR01 – Evaluation of core genome and whole genome multilocus sequence typing schemes for Campylobacter jejuni and Campylobacter coli outbreak detection in the USA (2023)
- All REPDBR01 – Ongoing outbreak of extensively drug-resistant Campylobacter jejuni infections associated with US pet store puppies, 2016–2020 (2021)
- Outbreak A – Antimicrobial susceptibility testing and successful treatment of hospitalised patients with extensively drug-resistant Campylobacter jejuni infections linked to a pet store puppy outbreak (2021)
- Outbreak A – Comparison of molecular subtyping and antimicrobial resistance detection methods used in a large multistate outbreak of extensively drug-resistant Campylobacter jejuni infections linked to pet store puppies (2020)
- Outbreak A – Multidrug-resistant Campylobacter jejuni outbreak linked to puppy exposure – United States, 2016–2018 (2018)
Selected publications on Campylobacter jejuni are for reference; other publications regarding the bacteria may be available.
Timeline
Map
Laboratory Data
Whole genome sequencing analysis
Bacteria in these strains are within 53 allele differences (REPDBR01-1), 116 allele differences (REPDBR01-2), and 140 allele differences (REPDBR01-3) of one another by core genome multilocus sequence typing.
This is more genetically diverse than typical multistate outbreaks, in which bacteria generally fall 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.
| Year | Number of isolates | Isolate type | Geographic location of source | Reason collected |
|---|---|---|---|---|
| 2007 | 1 | Dog | Wyoming | Unknown |
| 2013 | 1 | Dog | Ohio | Unknown |
| 2017 | 10 | Dog | Florida, Ohio, Wisconsin | Outbreak A |
| 2017 | 5 | Dog | Florida, Wisconsin, Wyoming | Unknown |
| 2018 | 4 | Dog | Florida, Georgia | Outbreak A |
| 2018 | 3 | Dog | Florida, Ohio | Unknown |
| 2018 | 1 | Turkey (food animal) | Missouri | Routine sampling |
| 2020 | 2 | Dog | Iowa, Minnesota | Outbreak B |
| 2021 | 1 | Dog | New Hampshire | State investigation |
| 2021 | 1 | Chicken (food product) | Missouri | Routine sampling |
| 2023 | 2 | Dog | Florida, Ohio | State investigations |
| 2024 | 2 | Dog | Ohio | Outbreak C |
| 2025 | 2 | Dog | Nevada | State investigation |
Genomic information
The National Center for Biotechnology Information (NCBI) advances science and health by providing access to biomedical and genomic information.
Resource
View the full single nucleotide polymorphism (SNP) cluster by accessing the isolates browser and clicking the link underneath the "SNP Cluster" column.
REPDBR01-1: PNUSAC003228
REPDBR01-2: PNUSAC012858
REPDBR01-3: PNUSAC009690
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), 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 in intestinal bacteria, the ways in which resistance spreads, and how resistant infections differ from susceptible infections.
These strains have developed antimicrobial resistance, which means certain drugs may no longer be effective for treatment. Bacteria from most ill people's samples were resistant to multiple antibiotics, including several recommended for first-line or alternative treatment for Campylobacter infections (azithromycin, ciprofloxacin, and erythromycin).
People with mild illness may not require antibiotics. If antibiotics are needed, REPDBR01 infections may not be treatable with commonly recommended antibiotics and may require a different antibiotic choice.
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 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 specimen.
Most state public health laboratories do not routinely receive or sequence all Campylobacter isolates. Therefore, some cases of REPDBR01 infection may not have been detected.
PulseNet transitioned to using whole genome sequencing (WGS) as the standard subtyping method for Campylobacter in July 2019. Before then, not all Campylobacter reported to PulseNet had WGS data available. Isolates are identified as part of these strains based on WGS. As a result, the number of people with lab-confirmed illness caused by these strains before 2019 may be underrepresented.
Outbreak dates are based on reported or estimated illness onset dates.
Confirmed sources were implicated by epidemiologic plus traceback or laboratory data. More information about determining outbreak sources available in the latest summary of possible multistate enteric disease outbreaks.
Among the 113 illnesses in Outbreak A, only 48 were culture confirmed and met criteria for inclusion.
Includes 290 human illnesses for which information was reported as of June 30, 2025.
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 290 human illnesses for which information was reported as of June 30, 2025.
Illness year is based on the date of isolate collection.
The single nucleotide polymorphism (SNP) trees provided by NCBI's Pathogen Detection Pipeline in the links above may include isolates that are not considered part of these strains. 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 links are provided to give context to the overall genetic relatedness of the strains reported here and to provide links to raw sequence files.
The SNP trees on NCBI's Pathogen Detection Pipeline are updated more frequently than this webpage.
Resistance was determined based on the results of antimicrobial susceptibility testing when available (90 isolates). Otherwise, resistance was predicted based on whole genome sequencing (200 isolates).
For florfenicol, the resistance determination was based only on antimicrobial susceptibility testing.
For kanamycin and streptomycin, the resistance determination was predicted based only on whole genome sequencing.
Resources
Testing for dogs (including household pets or animals residing in a store or shelter) that had contact with a person infected with Campylobacter is available through the Veterinary Laboratory Investigation and Response Network. Contact Vet-LIRN at vet-lirn@fda.hhs.gov.
Recommendations for breeders, distributors, and pet store owners
Recommendations for pet owners
Recommendations for clinicians and public health professionals