Testing for Canine MRSA Infection With Blood, Skin, Urine or Sputum Cultures

Methicillin-resistant Staphylococcus aureus (MRSA), a type of bacteria, causes an MRSA skin infection (a kind of staph infection) that is difficult to treat with methicillin and other common antibiotics. Testing for an MRSA blood infection is performed by taking an MRSA sputum culture, or a blood or skin sample, depending on your dog's symptoms. Transmission of the MRSA contagious infection occurs from humans to dogs, and from dogs to humans. About 1,000 pets die each year from contracting MRSA. The sooner MRSA is diagnosed in your dog, the sooner effective treatment can be administered.

Risk Factors for MRSA

Staphylococcus bacteria exist in all species with no symptoms, including dogs. Fortunately, most dogs infected with staph bacteria, including MRSA, are able to fight off an infection. The downside is that both humans and animals infected with MRSA can be silent carriers. Dogs that do become ill from MRSA have the following risk factors:

  • Contact with owners or family members who are carriers
  • Contact with other pets or animals that are carriers
  • Contact with human or animal carriers at a vet hospital or kennel
  • Compromised immune system
  • Exposure to MRSA bacteria after sustaining wounds in an injury or undergoing surgery

Diagnosis of Canine MRSA

If your vet suspects your dog has contracted a MRSA infection or could be a carrier, samples of your dog's blood, affected skin, urine or sputum are sent to the lab in order to identify the exact bacteria present. Then, cultures are treated with different antibiotics to see which one works best in killing the bacteria. In the meantime, antibiotics other than penicillin and methicillin may be administered to your dog. Specimens taken from your dog may include the following:

  • Fluid from an abscess
  • Secretions from the nose, throat, bronchial tubes
  • Fluid from the pleural cavity
  • Blood
  • Tissue biopsy of a suspected internal infection site, like a joint or bone

Vets are also using a new method, the rapid BD GeneOHm test, which can detect MRSA genetic material in a blood sample in as little as two hours. The test can also tell whether the genetic material comes from a less dangerous type of staph bacteria that can be readily treated with methicillin. The test helps reduce the time between diagnosis and treatment.

Conditions Associated with Canine MRSA

Your vet will also evaluate your dog's general health status in diagnosing and treating MRSA in your dog. The MRSA bacteria causes minor skin problems, deep-wound infections and severe systemic damage. Here are conditions and complications associated with MRSA infection in dogs, some of which can be life-threatening:

  • Oozing surface sores and boils
  • Inflamed wounds or incision sites
  • Pneumonia
  • Meningitis
  • Septicemia ("blood poisoning")
  • Osteomyelitis
  • Septic arthritis
  • Heart and other organ damage
  • Necrotizing fasciitis (flesh-eating disease)
  • Purpura fulminans (hemorrhaging from vessels into the skin and clot formation)
  • Sepsis (whole-body infection)

Treating MRSA

Most cases of MRSA can be treated with the following antibiotics, alone or in combination: vancomycin, linezolid and mupirocin. Research is ongoing in non-antibiotic treatments as well. Whatever treatment regimen is prescribed for your dog, it is imperative that your dog takes the entire prescription of antibiotics on schedule. Do not think improvement after a few doses means your dog is cured. If you quit giving your dog an antibiotic prescribed for MRSA, a low dose left in your dog's system may allow bacteria to become resistant to that particular antibiotic. In addition, you should monitor your dog's symptoms during treatment judiciously. Contact your vet immediately if they do not improve or worsen. Bacteria's resistance to antibiotics can change rapidly, possibly necessitating a change in your dog's prescription.