MRSP and MRSA in companion animals: plain facts for clinic teams

MRSP and MRSA in companion animals: what is the difference?

The difference between MRSP and MRSA in companion animals is the species of staphylococcus, and the culture report names it. Both resist beta-lactam antibiotics, and both often carry resistance to other classes as well.

Most methicillin-resistant staph infections in dogs are MRSP, not MRSA, and MRSP is not more severe or more contagious than susceptible strains; it is harder to treat.

How common is MRSP, and who is at risk?

MRSP is fairly common in dogs with recurrent disease and much rarer in the general dog population. S. pseudintermedius causes about 90% of skin infections in dogs with allergies and is a common cause of ear infections, according to the Worms & Germs and CAVD fact sheet. The methicillin-resistant form turns up mostly in dogs that keep coming back.

• Studies have found up to 17% of healthy dogs carrying MRSP, though in the general population probably only 1 to 2% carry it at any time.
• In dogs with recurrent skin infections, up to 41% of infections are due to MRSP.
• Risk factors include antimicrobial use, longer hospital stays and regular clinic visits for chronic disease.
• Up to 62% of dogs may remain carriers after treatment for an MRSP skin infection, some for months or longer.
• About 4% of veterinarians working with dogs and cats are colonized with MRSP, usually without any problem.

Look at those risk factors and you'll recognize your regulars: the itchy allergic dog on his fourth course this year, the long-stay surgical patient. They're the ones for whom culture and tight infection control matter most.

Diagnosis and treatment principles

Diagnosis takes culture and susceptibility testing, because MRSP infections look exactly like infections with susceptible S. pseudintermedius. The fact sheet notes results can take about 7 days.

So culture early in recurrent or non-responsive pyoderma, otitis and surgical site infections, rather than after several empirical courses. And treat infection, not colonization. The fact sheet says decolonization therapy with antibiotics isn't recommended in pets: there's no known effective way to clear MRSP or MRSA colonization in dogs, and trying adds resistance pressure.

Topical therapy deserves a real look. Some MRSP infections respond to topical treatment as well as susceptible strains do, and intensive topical therapy alone may be an option when a strain resists almost every systemic drug. For highly resistant strains, bring in a veterinary dermatologist or a pharmacology expert. Either way, recheck at the end of treatment to confirm it's resolved, and deal with whatever's underneath, such as allergy.

Put culture results and the drug you chose in the patient record, so the next vet on the case sees the susceptibility history before prescribing. PetGrid's prescriptions sit in the same chart.

Infection control in the clinic

Infection control in the clinic mostly comes down to standard precautions done well, since MRSP spreads mainly by direct contact with an infected or colonized animal. Spread from a contaminated object is possible, the fact sheet says, but appears very rare.

Hand hygiene comes first, before and after every patient. The Canadian Committee on Antibiotic Resistance's clinic guidance calls it the single most important measure and says gloves aren't a substitute. For known MRSP or MRSA patients and their lesions, add gloves and a gown or lab coat, and take them off before you touch anyone else.

Exam tables and equipment get cleaned, then disinfected. MRSP can survive in the environment for a long time, but most common disinfectants handle it on a surface that's been cleaned first. Flag known carriers in the record, and where you can, book them so they don't overlap with surgical or immunocompromised patients. Hospitalized patients with active infections should be isolated when possible.

The Ontario Animal Health Network hosts the 2020 IPC best practices for small animal clinics, audit checklist included. Our post on zoonotic disease risks for clinic staff covers protecting the team more broadly.

What to tell owners

Tell owners first that MRSP isn't MRSA, because most of them will have read about the human one. The fact sheet's message is reassuring and practical: most pets with MRSP infections are treated successfully, and human infection is rare.

• Give every dose as prescribed and finish the course unless told otherwise, then come back for the recheck.
• Wash hands after handling the pet; people who wash their hands after touching their pets carry S. pseudintermedius less commonly.
• Avoid touching the infected area, and keep it covered where possible.
• Clean bedding, toys and bowls 2 to 3 times a week with warm, soapy water during treatment.
• Anyone in the home who is immunocompromised should take extra care and speak to their own doctor.

It sticks better in writing. Send the fact sheet and the plan home with them, and with owner messaging, the instructions and recheck date reach the client in the PetGrid app.

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En resumen

MRSP and MRSA in companion animals are different bacteria. MRSP is common in dogs and rare in people; MRSA is the other way round. Culture early, treat infection rather than carriage, use topical therapy where it fits, and keep standard infection control tight.

PetGrid keeps culture results, prescriptions and owner instructions in one record and one conversation. See how it works in a short demo.