Drug-resistant bacteria has circulated among pet store customers/employees for at least 10 years

A CDC survey study found that puppies from commercial pet stores were linked to outbreaks of extensively drug-resistant Campylobacter jejuni (C jejuni) infections among store customers and employees.

Rates of Campylobacter infection—the top bacterial cause of diarrhea, typically caused by C jejuni—have doubled over the last two decades, and a substantial portion of these infections have increased resistance to fluoroquinolones and macrolides. In August 2017, the Florida Department of Health received six reports of patients developing Campylobacter infections following contact with puppies sold by a national pet store chain based in Ohio, according to Mark E. Laughlin, DVM, MPH-VPH, of the Division of Foodborne, Waterborne, and Environmental Diseases at the CDC, and colleagues.

“Samples from puppies yielded isolates highly related by whole-genome sequencing (WGS) to an isolate from a patient in Ohio who had recently purchased a puppy from the same pet store chain,” they wrote. “In response, the [CDC], along with federal and state partners, initiated a national outbreak investigation of C jejuni infections linked to pet store puppies.”

From Aug. 1, 2017-Feb. 29, 2020, the CDC and partners conducted two investigations. Their findings were published in JAMA Network Open.

“This survey study found that human extensively drug-resistant C jejuni infections were associated with contact with puppies sold through the commercial dog industry,” they wrote. “Surveillance data indicate the extensively drug-resistant C jejuni strains have been circulating for at least 10 years and continue to cause illness among pet store customers, employees, and others who encounter pet store puppies. The extensively drug-resistant isolates are resistant to all recommended treatment agents.”

Laughlin and colleagues concluded that their findings “suggest that practitioners should ask about puppy exposure (including occupational exposure) when treating patients with Campylobacter infection, especially those who do not improve with routine antibiotic treatment. When a polymerase chain reaction–based diagnostic test result is positive, an isolate should be obtained from a reflex stool culture for antibiotic susceptibility testing, public health surveillance, and outbreak detection. The commercial dog industry also needs to take action to help prevent the spread of extensively drug-resistant C jejuni from pet store puppies to people, including employees.

“This study highlights an ongoing problem within the companion animal sector that will require a collaborative solution,” they added. “These results indicate that public health officials, the commercial dog industry, animal welfare advocates, regulatory officials, physicians, and veterinarians should adopt a One Health approach to prevent the development and slow the spread of antibiotic resistance.”

The CDC has engaged in Campylobacter surveillance since 1996 and conducted case finding and investigation across four periods; for this analysis, researchers merged data on culture-confirmed cases collected during two investigations, a period of enhanced surveillance, and retrospective case finding, the study authors explained.

For the first investigation, state and local health officials interviewed patients with confirmed cases from Jan. 1, 2016, through Feb. 12, 2018. A case was defined as “culture-confirmed C jejuni infection in a patient with (1) an epidemiologic association with a pet store puppy (defined as contact with a pet store puppy before or after purchase, including contact resulting from pet store employment or during pet store visitation) or (2) an isolate highly related by core genome multilocus sequence typing (cgMLST) to an isolate from a patient with an epidemiologic association.”

Patients were interviewed using a focused questionnaire including demographic questions and exposures 7 days prior to illness (i.e., contact with a dog or puppy, type of exposure, pet store, or breeder affiliation). In October 2017, health officials collected fecal samples from puppies at implicated pet stores in Kentucky, Ohio, Pennsylvania, and Wisconsin and conducted traceback of any pets that had a sample with a relevant C jejuni strain or an epidemiologic association with a patient with Campylobacter infection.

As more cases arose, CDC conducted another investigation from Jan. 1, 2019, through Feb. 29, 2020. In this investigation, cases were defined as “culture-confirmed C jejuni infection with a strain highly related by cgMLST to an isolate from a patient in investigation 1 or to an isolate linked to a pet store puppy.”

All study isolates underwent testing for susceptibility to nine antibiotic agents (gentamicin, telithromycin, clindamycin, azithromycin, erythromycin, ciprofloxacin, nalidixic acid, florfenicol, and tetracycline). Isolates were classified as susceptible or resistant to antibiotics “using the European Committee on Antimicrobial Susceptibility Testing epidemiological cutoff values or clinical break points,” the study authors noted. They defined extensively drug resistant as resistance to macrolides and fluoroquinolones—the antibiotic classes recommended for Campylobacter) and three or more additional antibiotic classes.

The final analysis included a total of 168 patients (median [interquartile range] age, 37 [19.5-51.0] years; 105 of 163 female [64%]) who had an epidemiologic or molecular association with pet store puppies. “A total of 137 cases occurred from Jan. 1, 2016, to Feb. 29, 2020, with 31 additional cases dating back to 2011,” Laughlin and colleagues wrote. “Overall, 117 of 121 patients (97%) reported contact with a dog in the week before symptom onset, of whom 69 of 78 (88%) with additional information reported contact with a pet store puppy; 168 isolates (88%) were extensively drug resistant. Traceback investigation did not implicate any particular breeder, transporter, distributor, store, or chain.”

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Laughlin and colleagues noted that most sporadic Campylobacter infections in the U.S. are linked to raw or undercooked poultry, international travel, and animal contact, and a high proportion of antibiotic-resistant infections stem from international travel.

“However, these extensively drug-resistant strains have been associated with only dogs,” they wrote. “More than 1 in 3 US households has a dog, and dogs, especially puppies, can carry Campylobacter. Dogs carrying Campylobacter are frequently asymptomatic, underscoring the importance of primary prevention among pet store puppies.”

They also pointed out that, to their knowledge, these extensively drug-resistant strains were only found among the commercial dog industry and have not been linked with exposure to dogs from animal shelters, “indicating these strains might have a niche in commercial breeding and distribution of pet store puppies… Use of antibiotics and other management practices in the commercial dog industry might have selected for extensively drug-resistant strains and facilitated spread among dogs from 1 or more breeding facilities to many stores. In animal agriculture, factors such as crowding and inadequate husbandry have been associated with spread of illnesses among animals that may require antibiotic treatment, resulting in selection of resistant strains; similar conditions could be occurring in the commercial dog industry.”

In order to help reduce these infections, Laughlin and colleagues suggested that the commercial dog industry “could implement measures to curb unnecessary antibiotic use and improve hygiene and infection control at all levels from breeding facility to pet store, similar to those taken by the food animal production industry under U.S. Food and Drug Administration guidance.”

They also recommended focusing on antibiotic stewardship in veterinary schools and increased veterinary oversight within the industry and added that a national surveillance system “capable of combining human and companion animal diagnostic data could also improve the detection and investigation of zoonotic illness.”

Study limitations included that cases were likely underreported as a result of a lack of surveillance and oversight in the commercial dog industry; the study authors could not obtain exposure data regarding pet contact for all cases; and traceback data “revealed that puppies were often comingled throughout the distribution chain, making the primary source of infected puppies difficult to identify.”

  1. A CDC survey study found that puppies from commercial pet stores were linked to outbreaks of extensively drug-resistant Campylobacter jejuni (C jejuni) infections among store customers and employees.

  2. These findings suggest that practitioners should ask about puppy exposure when treating patients with Campylobacter infection, especially those who do not improve with routine antibiotic treatment.

John McKenna, Associate Editor, BreakingMED™

Study coauthor de Fijter reported grants from the CDC’s Epidemiology and Laboratory Capacity Cooperative Agreement during the conduct of the study. No other disclosures were reported.

Cat ID: 125

Topic ID: 79,125,730,125,190,192,151,925