Dermatology and Pyoderma (bacterial infections)

Facial fold pyoderma
German shepherd dog pyoderma
Un exemple de lésion

Pyoderma (bacterial infection of the skin) are probably the dermatoses most commonly encountered in veterinary practice. In England they represent 21% of all consultations in veterinary dermatology (results taken from a survey of the prevalence, diagnosis and treatment of dermatological conditions in small animals in general practice) (Survey of the prevalence, diagnosis and treatment of dermatological conditions in small animals in general practice).

Staphylococcus Intermedius is the most common bacteria isolated in association with bacterial infections of the skin of dogs

Classification of Pyoderma according to the depth of tissue reached:

  • Surface Pyoderma: Pyotraumatic dermatitis, Folds pyoderma (intertrigo), Mucocutaneous pyoderma 
  • Superficial Pyoderma:  Impetigo, bacterial folliculitis, Superficial Spreading Pyoderma 
  • Deep Pyoderma: Pyotraumatic folliculitis and furonculosis, furonculose of the chin (chin acne), localized or generalized deep Pyoderma and, finally, German Shepherd pyoderma

Diagnosis requires : 

  • a clinical and detailed dermatological examination 
  • microscopic examination with coloration (cytology)
  • identification of the bacteria with bacterial cultures 
  • cutaneous biopsies (less common)

The treatments call for:

  • topical treatments such as shampoos, ointments, lotions (for small surfaces without hairs)
  • antibiotics: the length of the treatment depends strongly on the type of Pyoderma
  • sometimes immunomodulators (vaccines)

Any underlying cause e.g : an allergy, hormonal trouble, a parasite……... must always be sought-after

In the particular case of Multi-resistant Staphylococci (as explained above), Staphylococci bacteria are frequently observed in connection with infections of the skin. Until recently, our classic antibiotics were efficient in fighting against these infections …. but new strains of Staphylococci have become resistant to many antibiotics (tested resistant to Methicillin) known as "Methicillin Resistant Staphylococcus” (MRS)

In human medicine, it is not so rare these days to contract a bacterial Multiresistant Staphylococcus Aureus (MRSA) infection following a simple stay in hospital.
Among dogs, Multiresistants Staphylococci Intermedius (MRSI) have also now become evident. They represent 17% of Staphylococci infections identified in the United State and have now appeared in Europe. A recent article published in the magazine Veterinary Dermatology mentions a frequency of 23% for cultures identified in a German veterinary clinic.
In Belgium, we saw them for the first time in 2007 and since then five examples out of 500 Pyoderma cases have been identified with certainty (four MRSI: an Otitis, two superficial infections, an interdigital infection and, a deep MRSA infection).  Two of the dogs lived in Luxemburg and three in Belgium. In 2008, an MRSI otitis was detected in a dog presenting rather insignificant symptoms and with relatively short evolution time of the complaint. A second case became evident on very localized but deep lesions situated on the neck.... The number of cases slowly progress each year.

The diagnosis rests on: 

  • diagnosis of bacterial infection (or not) of the skin
  • the cytology:  identification under the microscope in the clinic of a cocci-type bacteria (Staphylococcus)
  • the culture and the antibiogramme with some evidence of multiple resistances: resistance to Methicillin, Oxacillin, or Cefoxitin (using containing disks of these antibiotics on agar jelly)
  • the use of VITEK to establish minimal inhibitory concentrations (MIC) of these antibiotics vis-a-vis bacteria
  • identification of the gene mecA by technical PCR procedures
  • identification of the species of Staphylococci (Aureus / Intermedius) via PCR research of the thermonucleus Nuc genes

A skin infection that doesn't evolve normally should always attract your attention: It is preferable to refer the management of such cases to a veterinary dermatologist specialist because :

  • he/she will guide the laboratory toward a precise identification
  • at all costs it is necessary to limit the spread of these bacterial strains in the canine population
  • the presence of MRSA (Staphylococcus Aureus) can present a danger to humans should they come into contact with the infected animal
  • the management of these cases is difficult (both treatment of the dog and the surroundings)

To date, contagiousness from dog to man by Staphylococcus Intermedius has not been proven. On the other hand, man could constitute a danger of infection to the dogs that we treat.

For veterinarians interested in these Methicilline Resistant Staphylococci, advice on hygiene and precautions has been published by the BSAVA (in November 2006). The main measures concern hygiene of the hands and the environment but also the prudent use of antibiotics

Pyodermite secondaire à une démodécie, malnutrition et teigne avant traitement
Le même Boxer après 4 mois de traitement