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MRSA IN DOGS
AND CATS
Note for Pet Owners:
This information is provided by
Provet for educational purposes only.
You should seek the advice of
your veterinarian if your pet is ill as only he or she can correctly advise
on the diagnosis and recommend the treatment that is most appropriate for
your pet.
MSRA is a
potential Zoonosis and so precautions must be taken to prevent
cross-infection from animals to people and vice-versa.
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Description
MRSA stands for methicillin-resistant Staphylococcus aureus. Bacterial
resistance to antibiotics has been recognised for over 60 years, and the ability
of organisms including Staphylococci to develop resistance to
new-generation antibiotics is well known. Of particular importance to humans is
the emergence of strains of MRSA that have developed multiple resistance to
antibiotics, and which can cause devastating disease and death in susceptible
patients
Cause
The bacterium Staphylococcus aureus is a normal commensal inhabitant of
the skin, nasal cavity and pharynx, and isolation of it from swabs taken from
these areas does NOT necessarily mean that an animal is showing clinical signs
of disease. The reported frequency of occurrence of Staphylococcus aureus isolated
from normal dogs and cats varies from less than 10% to 40% of cats
and 90% of dogs (Krogh & Kristensen 1976). However,
Staphylococcus aureus infections, including MRSA and multiple-resistant
strains, do occur in dogs and cats. It is not clear to what extent humans are
the primary reservoir source for infection transfer to dogs and cats, or to what
extent dogs and cats act as reservoirs of infection for susceptible people. In
one review of the subject (Duquette and Nuttall 2004) humans were cited as
being the most common source of infection for dogs and cats. The
reported isolation rate of methacillin-resistance Staphylococcus aureus
from normal dogs and cats also varies from 93/6519 (1.42%) in domestic animals
(Rich and Roberts 2004), to 3/148 (2.03%) cats (Lilenbaum et al 1998). The
occurrence of methicillin-resistant strains of Staphylococci (not just S.aureus)
increases in the presence of disease, and in one study 15/40 dogs with recurrent
pyoderma were infected with methicillin-resistant bacteria (Frank et al 2003).
In another study 23/25 methacillin-resistant Staphylococci (9 of which
were MRSA) isolated from dog wounds or skin lesions possessed the mecA
gene, which has been linked to methicillin-resistance in human infections. In
one study, 5/5 patients with MRSA infected wounds that were tested grew
MRSA positive cultures when they had a swab taken from their nasopharynx (Boag
et al 2004)
Breed Occurrence And Other
Factors
There is no reported breed predisposition to develop MRSA infections, however
they are associated with :
- Wound infections (including post-elective surgery)
- Hospitalisation
- The use of immunosuppressant drugs
The relative importance of these factors, and the significance of human or
pet contact with Hospital premises is unclear.
Signs
Wound infections, including post-operative wound infections are the most common
manifestation of MRSA infections in dogs and cats and account for over 66% of
all reports so far :
Study |
Total Number of MRSA Cases |
Number Isolated From Wound Infections (%) |
Boag et al (2004) |
14 |
11 (78.6%) |
North Carolina State University,
Duquette & Nuttall (2004)
|
3 |
2 (66.7%) |
Rich and Roberts (2004) |
93 |
71 (76.3%) |
Tomlin et al (1999) |
11 |
11 (100%) |
University of Liverpool, Duquette & Nuttall (2004) |
4 |
4 (100%) |
Veterinary Staff
Considerations
Veterinary staff should consider themselves to be potential carriers of
MRSA, and take suitable precautions to prevent transmission of this potential
pathogen to their patients.
Susceptible members of staff should consider themselves at risk of
contracting MRSA from their patients, and take precautions to prevent such
cross-infection
Strict hygiene controls should be employed on veterinary premises,
especially in surgical areas with respect to instrumentation sterilisation and
handling, and wound management to minimise the risk of post-operative wound
infection.
Unnecessary intimate contact between veterinary staff and patients
which might facilitate the transfer of bacteria from skin or nasal cavities
should be discouraged.
The rational use of antibiotics is important to minimise the risk of
further drug resistance developing.
Diagnosis Culture
and Sensitivity The diagnosis of MRSA infections needs to be carried
out in an experienced laboratory and care needs to be taken when interpreting
results. For example, specific broth or agar plate culture techniques are
preferred to Kirby-Baur disc techniques because of different specificities and
sensitivities, and the latter techniques over-estimate methicillin resistance. During
sample collection and investigation care MUST be taken to avoid :
- contamination of swabs from non-diseased areas of the patient known to
carry MRSA organisms eg skin, upper respiratory tract, AND
- contamination from humans who may be carrying the organism.
PCR PCR is used to identify the presence of the mecA
gene.
Treatment Patients
infected with MRSA can be treated with alternative antibiotics, based upon
culture and sensitivity findings. For example , one case of joint infection
following elective cranial cruciate repair was successfully treated by
surgically inserting an absorbable gentamicin-impregnanted sponge (Owen MR et al
2004)
Zoonosis Considerations
Several reports have demonstrated that Staphylococcus aureus infections can
be transferred from pets to humans (Simoons-Smit et al 2000, Bradshaw 2003), and
these would suggest that humans could acquire MRSA infections from their pets
and vice versa.
There are also reports of transmission of MRSA from animals to humans. A
cat was implicated as a reservoir of MRSA for the re-infection of humans in a
geriatric ward (Scott et al 1998) and carrier dogs have been implicated as a
reservoir for the infection of people in family homes (Cefai et al 1994;
Manian 2003)
References
Boag A, Loeffler A, and Lloyd DH. Methicillin-resistant Staphylococcus
aureus isolates from companion animals. Veterinary Record (2004) 154: 411 Bradshaw
SE . Endocarditis due to Staphylococcus aureus after a minor dog bite.
Southern Medical Journal (2003) 96: 407-9 Cefai C , Ashurst S and Owens C.
Human carriage of methicillin-resistant Staphylococcus aureus linked
with pet dog. Lancet (1994) 344:539-540 Duquette RA and Nutall TJ.
Methicillin-resistant Staphylococcus aureus in dogs and cats : an
emerging problem ?. Journal of Small Animal Practice (2004) 45:591-7 Manian
FA. Asymptomatic nasal carriage of mupirocin-resistant methicillin-resistant Staphylococcus
aureus in a pet dog associated with MRSA infection in household contacts.
Clinical Infectious Disease (2003) 36: E26-E28 Owen MR, Moores AP and Coe
RJ. Management of MRSA septic arthritis in a dog using a gentamicin-impregnated
collagen sponge . Journal of Small Animal Practice (2004) 45: 609-612 Rich M
and Roberts L . Methicillin-resistant Staphylococcus aureus isolates
from companion animals. Veterinary Record (2004) 154: 310. Scott GM et al.
Cross-infection between animals and man : possible feline transmission of Staphylococcus
aureus infections in humans ? Journal of Hospital Infection (1998)
12:29-34 Simoons-Smit AM et al. Transmission of Staphylococcus aureus between
humans and domestic animals in a household. European Journal of Clinical
Microbiology and Infectious Diseases (2000) 19: 150-2 Tomlin J et al.
Methicillin-resistant Staphylococcus aureus infections in 11 dogs.
Veterinary Record (2004) 144: 60-64 Updated
October 2013
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