146 BASICS
In a similar period (2004), less than 0.6% ofS. intermedius(likelypseudintermedius)
were methicillin resistant, increasing to 10.2% in 2007.
Most canine cases involve MRSP and MRSS, rarely MRSA.
Most canine clinical presentations are seen as pyoderma, otitis, and surgical wound
infections (deep soft tissue, body cavities, and orthopedic repairs).
MRSP and MRSS are most commonly associated with superficial infections (skin and
ear canal) in dogs (Figures 7.1–7.5).
MRSA in canine patients is more commonly associated with deep infections – geni-
tourinary, respiratory, joint space, body cavity, and wounds.
TRANSFER OF INFECTION BETWEEN SPECIES:
INCREASING CONCERN
The zoonotic potential ofS. pseudintermedius,S. aureus,andS. schleiferiis becoming
increasingly concerning; all three species have the potential to cause disease in both
humans and animals.It is important to remember that not all transfers result in actual disease and may
represent only colonization: one study found MRSP in 4.5% of healthy dogs and 1.2%
of healthy cats.As a zoonotic example, household cats have been identified with MRSA isolates that
contain the staphylococcal chromosome cassette (SCC) mec element that is associ-
ated with nosocomial MRSA infections in people; these findings suggest a reverse
zoonotic transmission from humans.Increased incidence noted with owners employed in the healthcare field, suggesting
a possible mode of transmission from the person to the pet;S. pseudintermediushas
been isolated from pet owners with and without active infection.Staphylococcus schleiferihas the ability to develop multidrug resistance and is a
known cause of infection in both dogs and humans independent of interspecies
transfer.There is concern about dogs involved in hospital visitation programs causing
increased risk to both the animal and the hospitalized patient; current recommen-
dations are to avoid contact between visiting animals and patients infected with MRS
species; pets should be bathed and groomed prior to each visit.Transmission can happen by many paths: environment to human, human to environ-
ment, human to human, human to pet, pet to human, pet to pet, pet to environment,
and environment to pet.Transmission is usually by direct contact with the nasal passages, throat, and skin or
by indirect contact from walls, floors, counters, bedding, dishes, etc.
Routine decolonization therapy is not recommended for humans or animals that have
mucosal colonization with MRSA; there is currently no evidence that such treatment
is effective, even with topical mupirocin.Adequate topical coverage of nasal passages, skin, or mucosa cannot be achieved.
Most pets will clear MRSA colonization spontaneously.