Frequently Asked Questions about Carbapenem-resistant Enterobacterales (CRE) for Veterinarians

CRE stands for carbapenem-resistant Enterobacterales. These are highly antibiotic-resistant Gram-negative bacteria that can cause difficult-to-treat infections in both humans and animals, like pneumonia, bloodstream infections, urinary tract infections, and wound infections.

• Carbapenems are β-lactam antibiotics with a broad spectrum of activity and low toxicity. They have been a mainstay of treatment for highly multidrug-resistant infections in humans since the 1990s. Carbapenems have become increasingly important for treatment of Gram-negative infections (e.g., Escherichia coli) as resistance to extended-spectrum cephalosporin antibiotics has increased. There are four carbapenem antibiotics currently available in the United States: meropenem, ertapenem, doripenem, and imipenem.
• Resistance refers to bacterial defense mechanisms used to evade the effects of an antibiotic. These resistance mechanisms can be intrinsic (a normal characteristic of the bacteria) or acquired. Bacteria can acquire resistance through several mechanisms, such as mutations of their chromosome and by acquiring the genetic code to destroy certain antibiotics.
• Enterobacterales are a large order of bacteria, including E. coli and Klebsiella spp., commonly found in the gastrointestinal (GI) tracts of both humans and animals. When Enterobacterales develop resistance to carbapenem antibiotics, the bacteria are called carbapenem-resistant Enterobacterales (CRE).

No. Both humans and animals can be colonized with CRE, which means they can carry the bacteria in their gut without it causing infection or symptoms. People and animals colonized with CRE may still shed CRE into the environment and can still spread the germ to others.

Currently, there are no known treatments to decolonize a person or animal carrying CRE. Antibiotic treatment does not decolonize the GI tract and may increase CRE shedding and prolong colonization. People and animals who become colonized with CRE may decolonize naturally over time. Decolonization is more likely to occur in healthy individuals who rarely use antibiotics.

Some types of CRE are more likely to spread because they can share their resistance to carbapenem antibiotics among different strains of bacteria. These are called carbapenemase-producing CRE (CP-CRE). CRE increases in the United States are attributed to emergence and spread of CP-CRE. These have been targeted by public health for aggressive prevention measures in healthcare settings.

For technical information about CRE, please visit CDC’s CRE Technical Information webpage.

As of October 2020, multiple reports of carbapenemase-producing-CRE (CP-CRE) identified among U.S. cats and dogs have been published in the peer-reviewed literature or reported to public health officials. However, the overall incidence in the United States is unknown. Public health officials and veterinary diagnostic laboratories are currently working to understand the capacity of veterinary laboratories to detect CRE and determine how commonly it is identified. A few reports have described CP-CRE spread among animals in U.S. and European veterinary hospitals.

CRE are transmitted through contact. In human healthcare settings, patient-to-patient transmission typically occurs through indirect contact, such as contaminated healthcare worker hands, inadequately cleaned and disinfected medical equipment, or patient care areas.

Currently, information about modes of CRE transmission in veterinary settings is limited. Extrapolation from outbreaks in veterinary settings and from human healthcare settings suggests that transmission may occur via direct contact with animals or animal feces, and via indirect contact with contaminated hands of veterinary personnel, medical equipment and devices, and environmental surfaces. In veterinary settings, allowing animals colonized or infected with CRE to use shared urination and defecation relief areas may facilitate CRE transmission to other animals.

Reports in the peer-reviewed literature indicate that CRE can be transmitted between companion animals and humans through household contact. Transmission can occur from humans to animals, and from animals to humans; however, the frequency of CRE transmission between humans and animals is not yet known.

Additionally, one report from Switzerlandexternal icon found that of 108 veterinary healthcare personnel screened, 2 were colonized with CP-CRE strains that were genetically nearly identical to CP-CRE recovered from dogs in their facilities, suggesting that transmission between animals and humans occurred in the veterinary healthcare setting (Endimiani, 2019). Although this is a single report, these findings stress the importance of using standard infection control precautions in veterinary settings. To access the Compendium of Veterinary Standard Precautions, please visit the National Association of State Public Health Veterinarians (NASPHV) webpage pdf icon[PDF – 27 Pages]external icon.

Talk with your veterinary diagnostic laboratoryexternal icon or state public health veterinarian pdf icon[PDF – 7 Pages]external icon about the availability of testing Enterobacterales isolates for carbapenem resistance and mechanisms of carbapenem resistance.

To prevent the spread of CRE and other infectious organisms between animals, veterinary personnel should follow the veterinary standard precautions outlined in the NASPHV Compendium of Veterinary Standard Precautions pdf icon[PDF – 27 Pages]external icon. This includes:

• Perform hand hygiene before and after contact with an animal or its feces, body fluids, vomitus, or exudates; after contact with articles contaminated with these substances; after contact with environmental surfaces in animal areas; and after removing gloves. Hand hygiene can be performed with soap and water, or with alcohol-based hand sanitizer containing 60-95% ethyl alcohol or isopropyl alcohol. If hands are visibly soiled, washing hands with soap and water is recommended.
• Clean and disinfect equipment and surfaces between uses and when visibly soiled, use water and detergent prior to disinfecting and use an EPA-registered disinfectant according to label instructions, with attention to storage conditions, prior dilution, and contact time. Special attention should be paid to high-touch surfaces (e.g., examination tables, doorknobs, cage latches, faucet handles, and sinks).
• Clean and disinfect animal cages, toys, and food and water bowls between uses and when visibly soiled.
  • Clean litter boxes at least once daily.
  • Facilities should consider ease of use when selecting a cleaner-disinfectant or disinfectant. Products with shorter contact times, or that are pre-mixed, may be used with greater adherence.
• Implement barrier precautions when procedures are performed that may result in exposure to potentially infectious materials.
• Isolate animals with suspected or confirmed communicable diseases, including animals colonized or infected with CRE, to protect other animals and veterinary personnel.
  • Bring animals directly into an exam room when presenting for care and do not allow them to mingle with other clients or their animals.
  • Whenever possible, use disposable articles, such as bowls, litter pans, and gowns when caring for an animal in isolation.
  • Whenever possible, dedicate medical equipment (such as stethoscopes) to the animal in isolation for the duration of their admission. If it is not possible to dedicate equipment to the animal in isolation, then be sure to clean and disinfect the equipment between animals.
  • Use a separate animal relief area for animals colonized or infected with CRE since they are likely to heavily contaminate the environment with CRE.
• Educate veterinary staff about CRE and these measures to prevent spread to veterinary staff and between animals.

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Implement the recommended infection control practices in the NASPHV Compendium of Veterinary Standard Precautions pdf icon[PDF – 27 Pages]external icon to prevent CRE from spreading to veterinary staff and other animals in your facility. Educate veterinary staff about CRE and these infection control measures.

Notify the client that their animal has CRE: describe any control measures you have implemented, any recommendations specific to their situation, and provide them with a copy of CDC’s CRE FAQs for Pet Owners. Additionally, notify the referring veterinary facility, if applicable.

Review your facility’s clinical cultures from the past 6 months to check for additional CRE cases and monitor your facility’s clinical cultures prospectively over the next 3 months to identify any new cases. If you think you may have had any transmission of CRE in your facility, contact your jurisdiction’s public health department or animal health official for assistance in preventing additional cases.

Additionally, determine the reporting requirements in your state and jurisdiction. In many jurisdictions, confirmed CRE may need to be reported to a public health or animal health official.

Healthy people rarely get CRE infections. Persons most at risk for CRE infections include individuals with weakened immune systems, invasive medical devices, and individuals who have recently or frequently take long courses of certain antibiotics. Healthy people are also thought to be at lower risk for carrying CRE asymptomatically in their gut, compared to individuals who have frequent or recent antibiotic use and chronic medical conditions.

Adhering to recommended infection control practices, including hand hygiene, personal protective equipment (PPE) use, and environmental cleaning, can lower the risk for acquiring CRE. Additionally, eating, drinking, smoking, applying makeup, and similar activities should be performed in an employee breakroom or designated area. These activities should not be performed where contamination is more likely to occur, such as animal-care areas or areas where animal laboratory specimens are tested or stored. Do not keep food or drink for human consumption in the same refrigerator as food for animals, biologics, or laboratory specimens. Dishes for human use should be washed and stored away from animal-care and animal food preparation areas.

For most pet owners, the risk of acquiring CRE from a pet and developing infection is thought to be low. Persons who are most at risk for CRE infections include individuals with weakened immune systems, individuals taking long, frequent, or recent courses of certain antibiotics, and individuals whose medical care requires devices like ventilators, urinary catheters, or intravenous catheters. Individuals with underlying medical conditions or invasive medical devices may wish to consult with their healthcare provider about their individual risk and additional steps they can take to stay healthy. Regardless of their risk of infection, all owners of CRE-colonized or infected animals are encouraged to take steps to reduce the risk of transmission in their homes.

Information for pet owners about CRE in companion animals is available here.

Pet owners can prevent potential CRE transmission in home settings by following these guidelines:

Hand Hygiene

To reduce the risk of getting sick from germs pets can carry, it is important for clients to clean their hands following interactions with their pet, including playing with, feeding, or cleaning up after them. If the client is concerned about illness, they should talk to their healthcare provider and mention the animals they’ve had contact with recently.

Always clean hands:

• After touching or playing with their pet
• After feeding or handling pet food
• After providing medical or nursing care
• After handling pet habitats or equipment (crates, cages, toys, food and water dishes, etc.)
• After cleaning up after pets
• Before preparing food or drinks
• Before eating and drinking
• After removing soiled clothes or shoes

Alcohol-based hand sanitizer or running water and soap can be used for cleaning hands. If hands are visibly soiled, then soap and water should be used. Adults should always help young children with hand washing.

Practice Good Pet Hygiene

In addition to hand hygiene, practicing good hygiene can help prevent the spread of germs between pets and people. Advise clients to keep pets and their supplies out of the kitchen and disinfect pet crates/carriers and supplies outside of the house when possible. They should clean pet food and pet water dishes at least once a day, but whenever possible should not clean supplies in the kitchen sink, food preparation areas, or the bathroom sink. Advise clients to always remove their dog’s feces from their yard and public places using a bag and dispose of it in proper areas, keep children away from areas that might contain dog or cat feces, and cover sandboxes so cats don’t use them as a litter box.

Advise clients to seek veterinary care if their pet is ill. Cats or dogs that have diarrhea may need to be seen by a veterinarian for infection. If their pet has a history of CRE, advise owners to tell the veterinary clinic/hospital staff when booking an appointment and at the time of arrival about their pet’s history of this organism.

Pet Owners at Higher Risk of Infection

Advise individuals at higher risk of CRE infection (weakened immune system, taking antibiotics frequently, or using invasive medical devices) to follow these tips to reduce risk of environmental exposure when caring for an animal infected or colonized with CRE:

• Avoid high-risk activities (changing cat litter, cleaning up pet poop, or bathing pet), if possible. If no one else can perform the task, wear disposable gloves and clean hands afterwards. Both alcohol-based hand sanitizer and soap and water are acceptable methods for cleaning hands, unless hands are visibly soiled, in which case soap and water is preferred.
• Avoid receiving pet licks/kisses on the face or any wounds.
• Ensure that the cat litter box is changed daily.

National Association of State Public Health Veterinarians. Compendium of veterinary standard precautions for zoonotic disease prevention in veterinary personnel pdf icon[PDF – 27 Pages]external icon. JAVMA. 2015;247(11):1254-1276.

Aurelien N, Michael B, Valentina D, et al. Shedding of OXA-181 carbapenemase-producing Escherichia coli from companion animals after hospitalisation in Switzerland: an outbreak in 2018external icon. Euro Surveill. 2019;24(39):pii=1900071.

Cole SD, Peak L, Tyson GH, Reimschuessel R, et al. New Delhi metallo-β-lactamase-5–producing Escherichia coli in companion animals, United Statesexternal icon. Emerg Infect Dis. 2020;26(2).

Gronthal T, Osterblad M, Eklund M, et al. Sharing more than friendship – transmission of NDM-5 ST167 and CTX-M-9 ST69 Escherichia coli between dogs and humans in a family, Finland, 2015external icon. Euro Surveill. 2018;23(27):pii=1700497.

Endimiani A, Brilhante M, Bernasconi OJ, et al. Employees of Swiss veterinary clinics colonized with epidemic clones of carbapenemase-producing Escherichia coliexternal icon. J Antimicrob Chemother. 2019;dkz470.