Persistent Strains of Campylobacter jejuni (REPDBR01) Linked to Pet Store Puppies

Posted January 12, 2024

Posted January 12, 2024

Food Safety Alert/Investigation Notice

CDC, public health, and regulatory officials in several states, and _____________________________ are investigating a multistate outbreak of Salmonella Infantis infections with this persistent strain linked to ________________. Do not eat, sell, or serve ______________________.


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 to PulseNet in 2007. As of June 30, 2023, information from 247 ill people with REPDBR01 infection was reported to PulseNet.

The median age of ill people was 36 years (interquartile range, 20–52 years), and 66% were female. Among 220 ill people who provided race and ethnicity, 85% self-identified as White non-Hispanic, 9% self-identified as Hispanic/Latino, 5% self-identified as Black non-Hispanic, and 1% self-identified as another non-Hispanic race. The isolate source was stool in more than 99% of cases. Twenty-three percent (23%) of ill people were hospitalized for a median of 3 days (interquartile range, 2–4 days); no deaths were reported. Illnesses caused by these strains occur year-round.

In the past, REPDBR01 has spread to people through contact with dogs, especially puppies (typically <6 months of age), carrying these strains. Ninety-seven (97%) percent of ill people reported contact with a dog before becoming ill; among those with additional information, 78% reported contact with a pet store puppy, and 7% reported contact with a puppy from another setting, such as a shelter or breeder. Among those with contact with pet store puppies, 61% were pet store customers, 32% were pet store employees, 4% were pet store visitors, and 3% had contact with a pet store puppy purchased by someone else. Some of the associated puppies showed signs of illness, such as diarrhea, and some appeared healthy.

These strains of Campylobacter jejuni are relatively diverse genetically. There are up to 53 allele differences within REPDBR01-1, 104 allele differences within REPDBR01-2, and 101 allele differences within REPDBR01-3 by core genome multilocus sequence typing (cgMLST). This is more genetically diverse than typical multistate outbreaks, in which bacteria generally fall within 10 allele differences of one another.

What is a persistent strain?

CDC uses “persistent” to describe some strains of bacteria that have caused illness for years. The strains continue to cause illness, even though the number of illnesses they cause might vary over time. The strains are sometimes linked to more than one source, making them harder to control.

Learn about these strains and CDC’s efforts to control them

What is the definition used for extensively drug-resistant Campylobacter jejuni?

CDC defines extensively drug-resistant Campylobacter as resistant to macrolides and fluoroquinolones (the antibiotic classes recommended for treatment of Campylobacter) and 3 or more additional antibiotic classes.

Fast Facts
Learn fast facts about this rep strain.
Bacteria Campylobacter jejuni
Antimicrobial Resistance Profile Extensively drug resistant (details below)
Persistent Strains REPDBR01-1
First Detection June 2007
                       Illnesses Reported in PulseNet 247
Outbreaks Investigated 2
Identified outbreak sources*

*Confirmed sources were implicated by
epidemiologic plus traceback or laboratory data.
Suspected sources were implicated
by epidemiologic data only. More info

Pet store puppies (confirmed): 2 outbreaks

Last Updated: June 30, 2023

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. 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 two 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.

Summary of Selected Multistate Outbreaks and Other Investigations
Outbreak Dates People Got Sick* Outbreak Source Reported Illnesses Number of States with Illnesses# More Information
Summary of selected multistate outbreaks
Outbreak A January 12, 2016 – January 7, 2018 Pet store puppies 113§ 17 CDC Investigation Notice
Outbreak B January 6, 2019 – January 2, 2021 Pet store puppies 56 17 CDC Investigation Notice

* 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 info

§ Among these 113 illnesses, only 48 were culture confirmed and met criteria for inclusion.

# 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.

Selected Publications* Regarding REPDBR01 Investigations
Publication Year Published
Selected Publications* Regarding REPDBR01 Investigations
Evaluation of core genome and whole genome multilocus sequence typing schemes for Campylobacter jejuni and Campylobacter coli outbreak detection in the USA
PubMed DOI
Ongoing outbreak of extensively drug-resistant Campylobacter jejuni infections associated with US pet store puppies, 2016–2020
PubMed DOI
Antimicrobial susceptibility testing and successful treatment of hospitalised patients with extensively drug-resistant Campylobacter jejuni infections linked to a pet store puppy outbreak
PubMed DOI
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
PubMed DOI
Multidrug-resistant Campylobacter jejuni outbreak linked to puppy exposure – United States, 2016–2018
PubMed DOI

*Selected publications on Campylobacter jejuni are for reference; other publications regarding the bacteria are available.


This timeline, called an epidemiologic curve, shows when people got sick.

People with Campylobacter jejuni illnesses caused by the REPDBR01 strains, by month of isolate collection, January 2007–June 2023*,†

* Includes n=247 human illnesses for which information was reported as of June 30, 2023.

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.

Download data [XLS – 24 KB]


This map shows where ill people lived.

Laboratory Data

Whole Genome Sequencing analysis

Bacteria in these strains are within 53 allele differences (REPDBR01-1), 104 allele differences (REPDBR01-2), and 101 allele differences (REPDBR01-3) of one another by cgMLST. This is more genetically diverse than typical multistate outbreaks, in which bacteria generally fall within 10 allele differences of one another.

Isolates from food and animal samples

Year Number of Isolates Isolate Type Geographic Location of Source Reason Collected
Isolates from food and animal samples
2007 1 Canine Wyoming Unknown
2013 1 Canine Ohio Unknown
2017 10 Canine Florida, Ohio, Wisconsin Outbreak A
2017 5 Canine Florida, Wisconsin, Wyoming Unknown
2018 4 Canine Florida, Georgia Outbreak A
2018 3 Canine Florida, Ohio Unknown
2018 1 Turkey (food animal) Missouri Routine sampling
2020 2 Canine Iowa, Minnesota Outbreak B
2021 1 Canine New Hampshire State investigation
2021 1 Chicken (food product) Missouri Routine sampling
2023 1 Canine Florida State investigation

Genomic information

The National Center for Biotechnology Information (NCBI) advances science and health by providing access to biomedical and genomic information. To view the full SNP cluster, click on the link below; then within NCBI’s platform click the link underneath the “SNP Cluster” column.

SNP Cluster (REPDBR01-1)*: Isolates Browser – Pathogen Detection – NCBI (
SNP Cluster (REPDBR01-2)*: Isolates Browser – Pathogen Detection – NCBI (
SNP Cluster (REPDBR01-3)*: Isolates Browser – Pathogen Detection – NCBI (

*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 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 CDC PulseNet. The link is provided to give context to the overall genetic relatedness of these strains reported on this page, as well as to provide links to raw sequence files. Moreover, the SNP trees on NCBI’s Pathogen Detection Pipeline are updated more frequently than this web page.

Antimicrobial resistance information

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 is spread, and how resistant infections differ from susceptible infections.

Bacteria from all ill people’s samples showed resistance to multiple antimicrobials, including several that are recommended for first-line or alternative treatment: azithromycin, ciprofloxacin, and erythromycin. People with mild illness may not require antibiotics. If antibiotics are needed, illness resulting from REPDBR01 may be difficult to treat with commonly recommended antibiotics and may require a different antibiotic choice.

Figure: Percentage of human Campylobacter jejuni REPDBR01 isolates that were antimicrobial resistant, by antimicrobial (n=247), as of June 30, 2023 — National Antimicrobial Resistance Monitoring System


Interested in collaborating on a project related to this strain? Contact CDC at

Testing 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