Letter to The Veterinary Times, March 27 2005
Methicillin-resistant Staphylococcus aureus isolates from companion animals SIR, - Following the recent letter to The Veterinary Record (March 6, p 310) and interest in the popular press (The Observer, December 14, 2003), we would like to report an apparent increase in the number of methicillin-resistant Staphylococcus aureus (MRSA) infections that we have been following at the Queen Mother Hospital for Animals (QMHA), Royal Veterinary College (RVC), Hertfordshire, in recent months.
We have seen 12 confirmed cases since November 2003, five in cats and seven in dogs. The isolates were cultured from urine (three cases), bronchoalveolar lavage fluid (one case), pleural effusion (one case), non-healing wounds (two cases), a fresh (<36 hours old) wound (one case), infections of previous sutures (two cases), a nasal swab in an animal with upper respiratory tract disease (one case) and a postmortem isolate from adrenal gland culture in a dog euthanased for presumed discospondylitis.
Following confirmation of infection, nasal swabs were taken in five of these cases and revealed MRSA colonisation of the nasopharynx in all of them. It is not clear whether mucosal colonisation had been the source of infection in these animals or whether they had become colonised subsequent to their infection. Although the origin of the infection remains uncertain, it seems likely that in most cases the organism had been present on admission to the hospital; it was isolated from swabs taken shortly after admission or from deep lesions that had not been exposed to the hospital environment before swabbing.
MRSA had also been isolated from chronic skin lesions unresponsive to routine antimicrobial therapy in two dogs referred for skin disease between November 2002 and November 2003. Both dogs had been seen as outpatients. The prevalence of MRSA carriage in the human community in the UK is largely unknown but appears to be increasing (Robinson and Enright 2004). Although canine infection with MRSA was first described in the UK and North. America in 1999 (Tomlin and others 1999), there is little information on the incidence of colonisation in companion animals and whether this may be related to colonisation of in-contact humans.
However, a recent case report documented MRSA transfer between a human couple with recurrent MRSA infections and their pet dog (Manian 2003). At the RVCQMHA, we have recently completed a screening programme in which we have sampled staff and patients for pathogenic staphylococci, with a focus on MRSA. The results will be available shortly and will be published in due course.
Considering the potential implications of MRSA infection and colonisation in companion animals for antimicrobial treatment strategies and the transfer of antimicrobial resistance in both medical and veterinary fields, we are writing this letter to raise further awareness of this issue within the profession.
D. H. Lloyd,
Department of Veterinary Clinical Sciences, Royal Veterinary College, Hawkshead Campus, North Mymms, Hertfordshire AL9 7TA