ISSN 2398-2942      

Meticillin-resistant Staphylococcus pseudintermedius


Anette Loeffler

Jon Hardy

Synonym(s): MRSP (previously MRSI); MR-S.pseudintermedius (previously MR-S.intermedius), methicillin-resistant S. pseudintermedius




  • Genus: Staphylococcus
  • Family: Micrococcaceae
  • Species: pseudintermedius
  • Antimicrobial-resistance: carries additional genetic marker mecA for meticillin-resistance and broad β-lactam resistance.


  • Gk: staphyle- bunch of grapes; coccus- grain or berry; Gk: pseud- like/similar to; Latin: intermedius:-in-between. S. intermedius Staphylococcus intermedius was first described in 1976 as the main skin pathogen in dogs with characteristics ‘in between’ S. aureus Staphylococcus aureus and S. epidermidis Staphylococcus epidermidis; S. pseudintermedius was formerly named S. intermedius. It was first described as a separate species in 2005 when results from molecular analyses became available.
  • Meticillin (INN; international non-proprietory name) or Methicillin (USAN; United States adopted names): semisynthetic penicillin introduced for clinical use in 1959 but no longer manufactured today. Marker for broad beta-lactam antibiotic resistance.

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Clinical Effects



  • Healthy dogs (and cats):
    • Although MRSP may be carried on skin and mucosae, this is considered rare (its meticillin-susceptible counterpart S. pseudintermedius is part of the microflora of most dogs, less frequent in cats, but MRSP is thought to only succeed as a coloniser (microflora) if there is selection pressure from antimicrobial therapy).
    • Known staphylococcal carriage sites in dogs: nostrils, oropharynx, mucocutaneous junctions such as the perianal skin, external genitalia, skin (including squames and hair shed into the environment).
    • Higher risk of MRSP carriage in animals that have previously suffered from MRSP infection.
    • May also inhabit the gastrointestinal tract.
  • Infected pets:
    • In pus, infected body fluids such as urine, other infection sites.
    • MRSP likely carried at skin and mucosal sites during active infection, supported by licking/grooming behavior.
  • Environment:
    • Nosocomial pathogen (veterinary clinics and veterinary hospitals).
    • Dry surfaces for many months (including home environment).
    • Adhere to squames and hair shed into the environment.


  • Reproduction by binary fission.

Pathological effects

  • Infections involving MRSP show the same pathology as those due to meticillin-susceptible S. pseudintermedius (MSSP). No difference in virulence between MRSP and MSSP.
  • Typically skin and ear infections, traumatic and post-surgical wound infections, possibly complicated by implants, suture material and biofilm.
  • Any other organs (eg urinary tract, respiratory tract) as for other staphylococci.
  • No lasting immunity.

Other Host Effects

  • Same as for other Staphylococcus spp and as for meticillin-susceptible S. pseudintermedius.
  • MRSP can colonize skin and mucous membranes of healthy animals and predispose to subsequent MRSP infection.
  • Has host-preference (dog) but is not host-specific, ie can contaminate or colonize other host species and cause infection in immune-compromised individuals (opportunistic).


Control via chemotherapies

  • All MRSPs are resistant to all beta-lactam antibiotics Resistant bacterial infections, regardless of individual in vitro susceptibilities.
  • Topical antibacterial therapy should be used whenever possible Therapeutics: antimicrobial drug Therapeutics: bacterial infection.
  • 2-4% chlorhexidine Chlorhexidine preparations and/or fusidic acid Fusidic acid containing creams have good efficacy if owner and pet are compliant.
  • When systemic therapy is indicated, antibacterial selection should always be based on susceptibility test results.
  • If no susceptibilities identified, extended testing may be discussed with the laboratory.


  • None commercially available.

Other countermeasures

  • For known MRSP patients: Barrier nursing or isolation:
    • Outpatients should be booked in for last appointment of the day.
    • Waiting and walking in the practice should be minimized.
    • Cleaning and disinfection of used rooms and equipment before next patient.
    • Personal hygiene: protective clothing and hand hygiene.
  • Prevent spread of MRSP from unknown carriers or infected patients:
    • As for other multidrug-resistant or contagious pathogens.
    • Frequent and correct hand washing is the single most effective measure to prevent spread within veterinary surgeries.
    • Cleaning will remove 90% of bacterial pathogens.
    • Disinfection will not replace cleaning.
    • MRSP can be killed effectively with biocides recommended for staphylococci if used according to manufacturer’s instructions.
  • Inform owner and in-contact people (staff) of zoonotic potential. Immuno-compromised people may want to seek advice from their general practitioner/physician.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Morris D O, Loeffler A, Davis M F et al (2017) Recommendations for approaches to meticillin-resistant staphylococcal infections of small animals: diagnosis, therapeutic considerations and preventative measures.: Clinical Consensus Guidelines of the World Association for Veterinary Dermatology. Vet Dermatol 28 (3), 304-e69 PubMed.
  • Borio S, Colombo S, La Rosa G et al (2015) Effectiveness of a combined (4% chlorhexidine digluconate shampoo and solution) protocol in MRS and non-MRS canine superficial pyoderma: a randomized, blinded, antibiotic-controlled study. Vet Dermatol 26 (5), 339-344, e72 PubMed.
  • Grönthal T, Moodley A, Nykäsenoja S et al (2014) Large outbreak caused by methicillin resistant Staphylococcus pseudintermedius ST71 in a Finnish Veterinary Teaching Hospital--from outbreak control to outbreak prevention. PLoS One (10), e110084 PubMed.
  • Moodley A, Damborg P, Nielsen S S (2014) Antimicrobial resistance in methicillin susceptible and methicillin resistant Staphylococcus pseudintermedius of canine origin: literature review from 1980 to 2013. Vet Microbiol 171 (3-4), 337-341 PubMed.
  • Beco L, Guaguère E, Lorente Méndez C et al (2013) Suggested guidelines for using systemic antimicrobials in bacterial skin infections: part 2-- antimicrobial choice, treatment regimens and compliance. Vet Rec 172 (6), 156-160 PubMed.
  • Singh A, Walker M, Rousseau J et al (2013) Methicillin-resistant staphylococcal contamination of clothing worn by personnel in a veterinary teaching hospital. Vet Surg 42 (6), 643-648 PubMed.
  • Bond R, Loeffler A (2012) What's happened to Staphylococcus intermedius? Taxonomic revision and emergence of multi-drug resistance. J Small Anim Pract 53 (3), 147-154 PubMed.
  • Feng Y, Tian W, Lin D et al (2012) Prevalence and characterization of methicillin-resistant Staphylococcus pseudintermedius in pets from South China. Vet Microbiol 160 (3-4), 517-524 PubMed.
  • Frank LA, Loeffler A (2012) Meticillin-resistant Staphylococcus pseudintermedius: clinical challenge and treatment options. Vet Dermatol 23 (4), 283-291, e56 PubMed.
  • Walther B, Hermes J, Cuny C et al (2012) Sharing more than friendship--nasal colonization with coagulase-positive staphylococci (CPS) and co-habitation aspects of dogs and their owners. PLoS One (4), e35197 PubMed.
  • Weese J S, Faires M C, Frank L A et al (2012) Factors associated with methicillin-resistant versus methicillin-susceptible Staphylococcus pseudintermedius infection in dogs. J Am Vet Med Assoc 240 (12), 1450-1455 PubMed.
  • Windahl U, Reimegård E, Holst B S et al (2012) Carriage of methicillin-resistant Staphylococcus pseudintermedius in dogs--a longitudinal study. BMC Vet Res 8, 34 PubMed.
  • Paul N C, Moodley A, Ghibaudo G et al (2011) Carriage of methicillin-resistant Staphylococcus pseudintermedius in small animal veterinarians: indirect evidence of zoonotic transmission. Zoonoses Public Health 58 (8), 533-539 PubMed.
  • Soedarmanto I, Kanbar T, Ülbegi-Mohyla H et al (2011) Genetic relatedness of methicillin-resistant Staphylococcus pseudintermedius (MRSP) isolated from a dog and the dog owner. Res Vet Sci 91 (3), e25-27 PubMed.
  • van Duijkeren E, Catry B, Greko C et al (2011) Review on methicillin-resistant Staphylococcus pseudintermedius. J Antimicrob Chemother 66 (12), 2705-2714 PubMed.
  • Loeffler A, Linek M, Moodley A et al (2007) First report of multi-resistant, mecA-positive Staphylococcus intermedius in Europe: 12 cases from a veterinary dermatology referral clinic in Germany. Vet Dermatol 18 (6), 412-421 PubMed.

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