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Staphylococcus pseudintermedius


Synonym(s): S. pseudintermedius (formerly Staphylococcus intermedius)




  • Genus: Staphylococcus.
  • Family: Micrococcaceae.


  • Gk: staphyle - bunch of grapes; coccus - grain or berry; Gk: pseud - like/similar to; Latin: intermedius - in-between. S. intermedius was first described in 1976 as the main skin pathogen in dogs with characteristics ‘in between’ S. aureus and S. 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.

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Clinical Effects



  • S. pseudintermedius is part of the normal skin and mucosal microbiota of most dogs, less frequent in cats.
  • Inhabits the distal nasal passages, external nares and skin (adheres to squames and hair), especially at mucocutaneous junctions such as the perineum and external genitalia.
  • May also inhabit the gastrointestinal tract.


  • Reproduces by binary fission.


  • Spread by direct and indirect contact.
  • Many animal infections are probably endogenous, ie caused by a resident strain.
  • Transmission between different hosts (eg dog - human) occurs but unlikely to lead to persistent S. pseudintermedius carriage in non-dog, non-cat hosts.

Pathological effects

  • Opportunistic: infection only occurs due to a primary underlying cause that disrupts the balance between host-defences and microbiota.
  • Typically skin and ear infections (surface, superficial and deep pyoderma), traumatic and post-surgical wound infections, possibly complicated by implants, suture material and biofilm.
  • Any other organs (eg urinary tract, respiratory tract).
  • Most often neutrophilic response +/-macrophage involvement (pyogranulomatous inflammation)
  • No lasting immunity.

Dog and cat

Horse, cattle, sheep, pig, guinea pig, etc

  • Infections less common.
  • S. pseudintermedius has a 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

  • Surface and superficial pyoderma, ear and superficial wound infections: most cases will respond to topical antibacterial therapy alone, provided patient and owner compliance is good  and topical products with proven efficacy against staphylococci are used
  • When systemic antimicrobial therapy is indicated: sensitivity testing is recommended in the interest of good antimicrobial stewardship.
  • Repeated antimicrobial therapy (eg in recurrent pyoderma) is a recognized risk factor for multidrug-resistance Meticillin-resistant Staphylococcus pseudintermedius.
  • Primary underlying causes need to be diagnosed and corrected to avoid recurrent/persistent S. pseudintermedius infection.


  • No vaccines are commercially available.
  • Autogenous bacterin therapy and staphylococcal phage lysates have been used to control recurrent staphylococcal superficial pyoderma. There is little evidence of their efficacy but likely effect via stimulation of innate cell-mediated immunity.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Beco L, Guaguère E, Lorente Méndez C et al (2013) Suggested guidelines for using systemic antimicrobials in bacterial skin infections (1): diagnosis based on clinical presentation, cytology and culture.​ Vet Rec 172 (3), 72-78 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.
  • Bond R, Loeffler A (2012) What's happened to Staphylococcus intermedius? Taxonomic revision and emergence of multi-drug resistance. JSAP 53 (3), 147-154 PubMed.
  • Mueller R S, Bergvall K, Bensignor E et al (2012) A review of topical therapy for skin infections with bacteria and yeast. Vet Dermatol 23 (4), 330-341, e62 PubMed.
  • Fitzgerald J R (2009) The Staphylococcus intermedius group of bacterial pathogens: species re-classification, pathogenesis and the emergence of meticillin resistance. Vet Dermatol 20 (5-6), 490-495 PubMed.
  • Wildermuth B E, Griffin C E, Rosenkrantz W S (2006) Feline pyoderma therapy. Clin Tech Small Anim Pract 21 (3), 150-156 PubMed.

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