Outbreak of Antibiotic Resistant Campylobacter Bacteria Linked to Pet Store Puppies

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Outbreak of Antibiotic Resistant Campylobacter Bacteria Linked to Pet Store Puppies

The Centers for Disease Control & Prevention (CDC) issued a report recently concerning the spread of antibiotic resistant Campylobacter jejuni bacteria from pet store puppies to humans. We have summarized the findings and provide analysis.

CDC Report Summary

  • 118 persons, including 29 pet store employees, in 18 states were identified with campylobacteriosis illness onset during January 5, 2016 – February 4, 2018.
  • In total, six pet store companies were linked to the Campylobacter jejuni outbreak.
  • Outbreak isolates were resistant by antibiotic susceptibility testing to all antibiotics commonly used to treat Campylobacter infections.
  • Puppies became infected with Campylobacter before reaching the pet stores.

Epidemiologic Investigation

  • Among 149 puppies with available information, 142 (95%) received one or more antibiotic courses before arriving or while at the pet store.
  • Among 142 puppies that received antibiotics, treatment information was available for 134 (94%).
  • 78 (55%) treated puppies received antibiotics for prophylaxis only.
  • 54 treated puppies (38%) received therapy for prophylaxis and treatment.
  • Two puppies (1%) were given treatment only.
  • Median antibiotic treatment duration was 15 days
    (range = 2–67 days).
  • Four antibiotics (metronidazole, sulfadimethoxine, doxycycline, and azithromycin) accounted for 81% of all antibiotics administered.
  • Use of broad-spectrum antibiotics also was noted, including tetracyclines, quinolones, aminoglycosides, and chloramphenicol.

Laboratory Investigation

  • Campylobacter jejuni isolates were obtained in 51 persons and 23 puppies. Outbreak isolates from 45 persons and 11 puppies grouped into three distinct clades (isolates with a common ancestry) by whole genome multi-locus sequence typing (wgMLST).
  • Eighteen outbreak isolates (10 human and eight puppy) representing all three clades were selected for antibiotic susceptibility testing, and all were resistant to azithromycin, ciprofloxacin, clindamycin, erythromycin, nalidixic acid, telithromycin, and tetracycline.
  • In addition, 16 of 18 isolates were resistant to gentamicin, and four of 18 were resistant to florfenicol.
  • Importantly, none of the cultures of 12 dog food samples yielded Campylobacter spp.

Traceback Investigations

  • Distributors of pet animals are companies that purchase puppies wholesale from breeders and sell them to pet stores and other locations.
  • Practices identified during review of the records indicated that pet store puppies travel from breeders to distributors to pet stores by third-party transport companies.
  • Information collected for eight puppies owned by infected persons and 20 puppies with fecal samples that were positive for Campylobacter jejuni traced back to 25 breeders and eight distributors.
  • No single breeder, distributor, or transporter was identified as the infection source. However, potential for Campylobacter transmission among puppies exists because puppies from different breeders were commingled at distributors, during transport, and in the pet stores.

Public Health Response

  • CDC has developed educational materials on prevention of campylobacteriosis. CDC and the individual states have shared these with pet industry partners, including retail pet stores.
  • Educational messages focused on handwashing, separating human eating areas from animal areas, and using personal protective equipment correctly, such as wearing gloves when cleaning cages in pet stores.
  • CDC has posted an outbreak advisory online, which included information for clinicians and veterinarians recommending culture and antibiotic susceptibility testing to guide antibiotic treatment decisions.


  • Dog-associated Campylobacter outbreaks have been reported previously, but those outbreaks involved fewer illnesses, and the isolates were not multidrug-resistant.
  • The investigation of this outbreak revealed widespread administration of multiple antibiotic classes, including all classes to which the outbreak Campylobacter strains were resistant.


This report clearly shines a light on how problematic and far-reaching antibiotic resistance is and focuses upon conditions at puppy mills or in other places where animals are crowded and congregate (fairs, petting zoos, pet adoption events etc).

First, some background.

Antibiotic resistance is not the fault of an individual’s body. To survive, the bacteria itself needs to mutate to bypass an antibiotic.

Antibiotic resistance is commonly spread by overly prescribed antibiotics and food such as meat. The CDC emphasizes public education initiatives to curb antibiotic prescriptions, whereas the U.S. Food and Drug Administration (FDA) focuses on the amount of antibiotics given to livestock. Currently, antimicrobials – including antibiotics – important to human medicine cannot be given to livestock for growth promotion through feed and drinking water, but can be used sub-therapeutically (for prophylaxis).

This latest CDC report illustrates that antibiotic resistance is more pervasive than previously thought and can easily pass zoologically from dogs to humans.

What is lost in all of this is that the practice of giving antibiotics prophylactically (preventatively) to puppy mill-based pet store puppies clearly has been going on well before the outbreaks started in 2016. Now, the bacteria circulating in the supply chain of these puppy mill puppies have outwitted the antibiotics.

The question becomes, “Why are those who supply puppy mill puppies giving a broad range of antibiotics prophylactically?” We believe that the less than acceptable hygienic conditions and nutrition often found on these breeding farms provide the most likely explanation.

Unfortunately, the CDC report abruptly stopped short at directly implicating these conditions. The educational materials the agency created only addressed veterinarians, healthcare providers and pet store owners on curbing antibiotic use and providing proper sanitation. The singular mention of the behind-the-scenes, supply chain operators was, “Educate breeders, brokers, and transporters who supply animals to pet stores about responsible use of antibiotics and the benefit of veterinary supervision of antibiotic use.”

While we wish the CDC would have been more forthright, the agency’s primary role is human public health, education and societal public health. So, what governmental agency oversees the conditions of puppy mills and should be able to enforce them? The United States Department of Agriculture (USDA), which follows the regulations set forth in the federal Animal Welfare Act (AWA).

We have read several well-intentioned and informative websites that advocate for the humane treatment of dogs and cats regarding puppy mills. We believe that the Puppy Mill Project provided the most factual information.

The Puppy Mill Project states:

  • Any breeder who wishes to sell to a pet store or to consumers over the internet with five or more breeding females must be licensed with the USDA. There are an estimated 10,000 puppy mills in the United States – this includes both licensed and unlicensed facilities.
  • The AWA’s standards are too minimal to ensure humane care and treatment. For instance, dogs may be kept in stacked cages, may be forced to relieve themselves in their cages, confined for 24 hours per day, mesh or wire flooring is allowed, no exercise requirement if dogs are housed with other dogs and certain minimal size requirements are met for the dog’s enclosure, and human interaction is not required (To be fair to the USDA, the agency does provide educational materials about socialization, health and exercise.)
  • The USDA is overburdened. The Puppy Mill Project submitted a Freedom of Information Act request in 2014. The organization found out that the USDA had an estimated 110 inspectors on staff to inspect all the facilities under its supervision, not just commercial dog breeders and brokers. In 2010, these inspectors were responsible for 8,782 facilities. The division of the USDA that is responsible for inspecting commercial dog breeding facilities is also responsible for animal exhibitors (circuses, zoos, petting farms, wildlife parks), research facilities (hospitals, universities, pharmaceutical firms), and animal transporters (airlines and trucking companies).

We took this one step further and specifically reviewed the AWA’s regulations for the terms: medication, drugs, antibiotics, antimicrobials, and vaccinations.

  • The words “antibiotics” and “antimicrobials” were not specifically addressed.
  • “Drugs, such as tranquilizers, shall not be used to facilitate, allow, or provide for public handling of the animals.”
  • Vaccination requirements only apply to the importation of dogs to the United States.
  • The only mention of medications in regards to dogs and cats is, “Accompanying documents and records. Shipping documents that must accompany shipments of dogs and cats may be held by the operator of the primary conveyance, for surface transportation only, or must be securely attached in a readily accessible manner to the outside of any primary enclosure that is part of the shipment, in a manner that allows them to be detached for examination and securely reattached, such as in a pocket or sleeve. Instructions for administration of drugs, medication, and other special care must be attached to each primary enclosure in a manner that makes them easy to notice, to detach for examination, and to reattach securely. Food and water instructions must be attached in accordance with § 3.13©.”

In essence, prophylactic use of antibiotics is not specifically addressed, so it is not regulated and is currently considered allowable by law. Clearly, though, if the conditions were hygienic, prophylactic antibiotic use would not have even been considered necessary.

It must be noted that some states and municipalities have additional laws about the treatment of puppy mill puppies. However, we could not find anything pertaining to antibiotic use.

If you would like a full-bred or mixed breed designer dog, please consider adoption. The second best option is to do your own research and seek out responsible breeders. They typically operate out of their homes so you can see how the dogs are cared for and raised. They also provide lineage documentation. Additionally, they are usually members of dog clubs that prohibit the sale of dogs to puppy stores.

W. Jean Dodds, DVM
Hemopet / NutriScan
11561 Salinaz Avenue
Garden Grove, CA 92843



Barnes, Kimberly. “Detailed Discussion of Commercial Breeders and Puppy Mills.” Animal Law Legal Center, Michigan State University College of Law, 2017, http://www.animallaw.info/article/detailed-discussion-commercial-breeders-and-puppy-mills-0.

Code of Federal Regulations, Title 9 – Animals and Animal Products, Chaper I – Animal
and Plant Health Inspection Service, Department of Agriculture, Subchapter A –
Animal Welfare
. U.S. Government Publishing Office, 1 Jan. 2016, http://www.gpo.gov/fdsys/pkg/CFR-2016-title9-vol1/xml/CFR-2016-title9-vol1-chapI-subchapA.xml.

Montgomery, Martha, et al. “Multidrug-Resistant Campylobacter Jejuni Outbreak Linked to Puppy Exposure — United States, 2016–2018.” Morbidity and Mortality Weekly Report, vol. 67, no. 37,
21 Sept. 2018, pp. 1032–1035. https://www.cdc.gov/mmwr/volumes/67/wr/mm6737a3.htm?s_cid=mm6737a3_w

Puppy Mills and the Law. The Puppy Mill Project, http://www.thepuppymillproject.org/relevant-laws.

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