Methicillin resistant Staphylococcus - MRSA - MRSP

Should you be afraid of the Multiresistant Staphylococci (MRSI / MRSA)?

Staphylococci
bacteria are frequently observed in association with bacterial 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 - specifically Methicillines - and are named "Methicillin Résistant Staphylococcus" (MRS).

In human medicine, it is not so rare these days to contract a bacterial infection of Staphylococcus aureus multiresistant (MRSA) following a simple stay in hospital. In dogs, the Staphylococci intermedius multiresistants (MRSI) are now also evident. They represent 17% of Staphylococci culture cases encountered in the United States and they have now appeared in Europe. A recent article published in the magazine Veterinary Dermatology mentions a frequency of 23% for such infections tested in a German veterinary clinic.

In Belgium, we identified them for the first time in 2007. Since then, numerous dogs were treated for this skin disease.

The diagnosis
rests on:

  • the detection of bacterial infection of the skin (or not). 
  • the cytology: identication under the microscope at the clinic of a ‘cocci’ type bacterium (staphylococcus). 
  • the culture and the antibiogramme showing evidence of multiple resistances:  to Méthicilline, Oxacilline, or Cefoxitine
  • with the help of retaining disks of the antibiotics applied on agar jelly. 
  • the use of VITEK to establish the inhibitory minimal concentrations (MIC) of the antibiotics versus bacteria. 
  • the identification of the gene mecA with PCR technics
  • the identification of the species of staphylococci (Aureus / Intermedius) by PCRresearch on the thermonucleus (nuc) genes

N.B. A skin infection that doesn't normally evolve should attract concern: It is essential to confide the management of such cases to a veterinary specialist in dermatology for the following reasons :

  • He/she will guide the laboratory toward a precise identification of the infection
  • It is absolutely necessary to limit the diffusion of these bacterial strains in the canine population. 
  • the presence of MRSA (Staphylococcus aureus) can present a danger to humans when contacted 
  • the management of these cases is difficult -  both treatment of the dog and the environment

To date, contagiousness to man (from dog)  by the Staphylococcus intermedius has not been observed. On the other hand, man could equally contaminate dogs. For veterinarians interested in these staphylococci resistant methicilline, advice in respect of 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.