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Antibiotic-Resistant Infections in Dogs

Methicillin-Resistant Staph aureus (MRSA) Infection in Dogs

Staphylococcus aureus, often abbreviated as Staph aureus or S. aureus, represents a strain of bacteria that can develop resistance to standard antibiotics, including methicillin and other beta-lactam types. When it becomes resistant to these antibiotics, it’s termed methicillin-resistant Staph aureus, or MRSA.

Typically, Staph aureus doesn’t cause illness unless individuals or pets are already unwell or injured, at which point the bacteria can seize the opportunity to cause an infection. Some individuals may carry Staph aureus without showing any symptoms, a condition known as colonization. While dogs aren’t usually colonized with Staph aureus, exposure to colonized individuals or those with active infections can lead to infection or colonization in dogs as well.

Symptoms and Types

Main symptoms are:

  • Fever
  • Discharge from a wound (even a wound that looks small can be severely infected, as the infection can go deep rather than wide)
  • Skin lesion(s)
  • Skin swelling
  • Slow to heal wound(s)
  • MRSA infections in dogs most commonly involve skin and other soft tissues. They can result in skin infections and abscesses.
  • MRSA may also cause post-operative infections of surgical wounds and secondary infections of wounds originating from other causes.
  • More rarely, MRSA can also infect the dog’s urinary tract, ears, eyes and joints.


The causes of MRSA infections in dogs often stem from their exposure to colonized or infected individuals, primarily humans, in household settings. Factors such as prior surgery, hospitalization, and antibiotic treatments increase the risk of MRSA infections in dogs. Therapy pets, especially those involved in hospital visitation programs, may face heightened susceptibility.

When dogs encounter MRSA organisms, they can either become colonized or infected. Colonization implies the presence of MRSA bacteria in the dog’s nasal passages or anal region without showing symptoms, appearing outwardly healthy. Alternatively, dogs with existing wounds are more prone to MRSA infection. In some cases, dogs may exhibit both colonization and infection concurrently.

Although most dogs contract MRSA through human interaction, once colonized or infected, they can transmit the bacteria to other animals and humans alike, perpetuating the spread of the disease.


The diagnosis of MRSA typically involves conducting a bacterial culture. To obtain samples for culture, healthcare professionals may swab the nose or anal region of a suspected carrier or directly culture an infected wound, if present. A conclusive diagnosis of MRSA is made when a Staph aureus organism resistant to methicillin is isolated. In practice, oxacillin, a closely related antibiotic to methicillin, is used to test for susceptibility. Staph aureus organisms that exhibit resistance to oxacillin are classified as MRSA.


In the case of dogs colonized with MRSA who are otherwise healthy, treatment is typically unnecessary. Generally, assuming the dog isn’t re-exposed to the bacteria, the infection will clear up naturally within a few weeks. However, it’s advisable to maintain good sanitary practices, including thorough household disinfection.

For dogs with MRSA infections, proper local wound care is crucial. This may involve draining any abscesses, keeping wounds clean and properly bandaged, and adhering to your veterinarian’s instructions. Antibiotics are usually selected based on testing to identify the most effective medications for combating the bacteria. It’s essential to complete the full course of antibiotics prescribed for your dog, even if symptoms improve before finishing the medication.

Living and Management

If your dog is colonized or infected with MRSA, there are several measures you can take to prevent transmission:

  • Prioritize hand hygiene as the primary method to prevent transmission to other pets or family members. Thoroughly wash your hands with soap and water on a regular basis.
  • When handling infected areas on your dog, wear gloves and ensure you wash your hands meticulously after cleaning wounds or changing bandages. Dispose of used bandages directly into the trash.
  • Avoid allowing your MRSA-positive pet to sleep with you.
  • Refrain from permitting your MRSA-positive dog to lick or “kiss” your face or skin.
  • Always walk your dog on a leash and promptly clean up all feces.
  • Regularly clean your dog’s bedding and toys to minimize the risk of transmission.


To prevent the transmission of MRSA infections to your pet, prioritize maintaining good hand hygiene. If you or a family member have an MRSA infection or are colonized, make sure to wash your hands thoroughly and frequently with soap and water. Additionally, refrain from kissing your dog or allowing your dog to kiss you, and avoid contact with any broken skin.

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