Over the past five years, the RVC Dermatology Service has seen an increase in dogs with skin or ear infection due to methicillin-resistant Staphylococcus pseudintermedius (MRSP). It recently established a decolonisation study aimed at reducing its spread.

MRSP was first recognised in North America in 2001. It was found in continental Europe in 2007 and has since been identified by vets across the UK.

It shares many features with the human and animal pathogen MRSA, including the risk factors for acquisition, such as repeated exposure of the patient to antimicrobial therapy, invasive procedures or chronic skin disease and frequent visits to clinical settings.

It is therefore important to not only identify and cure the infection early but also to correct underlying triggering causes to prevent pyoderma recurrences and implement rigorous infection control measures to reduce the risk of contagion.

Owner education and a comprehensive management of the household setting are also extremely important. Many of the cases referred to the RVC have come with a challenging epidemiology, such as multi-pet households, show dogs or with immune-compromised owners undergoing medical treatments themselves.

During initial 90-minute dermatology consultations at the RVC, a detailed historical and clinical assessment is followed by in-house tests, including cytology for every patient, so that indicators of bacterial infection and potentially multidrug-resistance can be recognised early.

Consultations also include a work-up of underlying diseases responsible for secondary bacterial infections, and a comprehensive discussion of zoonotic implications with owners. The RVC dermatology specialists typically recommend a prolonged follow-up for MRSP patients and monitoring for MRSP carriage beyond the resolution of infection, either with our dermatology team or in collaboration with the referring vets. This is important because dogs that had an MRSP infection once frequently develop it again at a later stage. This could be due to persisting colonisation or environmental contamination.

Protocols are in place at the RVC’s Queen Mother Hospital for Animals (QMHA) for all suspected and confirmed MRSP patients to ensure that further diagnostics and management can be performed with minimal risk to others. The protocols were designed by a multidisciplinary Infection Control Committee.

MRSP is one of a range of multidrug-resistant bacterial pathogens found in small animal practice, most of them identical to pathogens causing problems in human hospitals. However, a particular concern about MRSP is that even after infection has resolved, patients can remain colonised or contaminated with MRSP on healthy skin, hair and mucosae, thus spreading MRSP to their environment, other animals and people. It also provides a source for their own re-infection with MRSP. While much is known about the transmission of MRSA in humans, little is known about MRSP carriage and spread in dogs.

The RVC Dermatology Service has a long-standing track record of research into antimicrobial resistance in staphylococci and canine pyoderma. In the late 1990s, the RVC group, then led by Professor David Lloyd, recognised and successfully managed the first cases of MRSA infections in dogs. This was followed, in 2007, by the first description of MRSP in Europe.

The new study launched by the RVC team investigates the role of MRSP contamination of the home environment on the persistence of MRSP carriage in dogs that have recovered from infection, and the potential need for decolonisation.

Dogs in the study will be allocated into two groups. In one group, the owners will follow a practical household cleaning protocol in three seven-day cycles. In the other, household cleaning will be combined with topical antibacterial treatment (fusidic acid gel, chlorhexidine/miconazole shampoo). All sampling materials and antibacterial medication will be provided free of charge, swab results will be shared with participating vets and owners to aid patient management.

The study is part of a BBSRC / Dechra co-funded CASE studentship, with the aim to identify strategies to reduce the risk of nosocomial and zoonotic infection. It has been approved by the RVC Clinical Research and Ethics Committee.

Commenting on the problem of MRSP and referring to the study, dermatology specialist Anette Loeffler said: “The emergence of this multidrug-resistant canine pathogen substantially limits treatment options for our patients and highlights the urgent need to review antimicrobial prescribing and hygiene strategies.”

Call for patients for clinical research project

If you are seeing or have recently seen a dog with MRSP, we would like to hear from you as your patient might be eligible. Participation will help you with a responsible follow-up of your MRSP-patient and reduce the spread of this veterinary nosocomial pathogen with zoonotic potential. In addition, we will provide you with advice and study material designed to reduce the risk of MRSP re-infection for your patient and to deal with owner concerns. We will enrol dogs that have recovered from MRSP skin, ear or wound infection but please do not hesitate to contact us before infection has resolved to discuss inclusion requirements.

Contact us 

If you see, or have recently seen, a dog with MRSP infection, please contact one of us to discuss eligibility.

• Anette Loeffler, Senior Lecturer in Veterinary Dermatology (01707 666246)
• Sian Clark, PhD student (01707 667037)
• Ross Bond, Professor in Veterinary Dermatology (01707 666410)