Concerns about veterinary antibiotic use and human safety have traditionally been associated with food animal production. Two studies in Europe have shown that less than 4% of antimicrobial resistance in people could be associated with animal sources and that resistance was mostly related to zoonotic organisms. Compared with concerns about the use of antibiotics as growth promoters in food animals, risks posed by the use of antimicrobials to treat infections in pets were largely considered to be "low." This appears to be changing. In the early 1990s, multidrug-resistant infections (Acinetobacter species, Escherichia coli, Salmonella species) in hospitalized dogs appeared, particularly in dogs in intensive care units. Several studies in Europe and the United States have documented increasing bacterial resistance, particularly of S intermedius, the major cause of canine bacterial pyoderma. Methicillin-resistant and beta-lactamase-resistant S intermedius have been seen in both cats and dogs treated for infections. Methicillin-resistant S intermedius has also been isolated from normal cats in Brazil and from cats in London (normal feral cats, normal pet cats, and pet cats with skin disease). The highest frequency of isolation was from normal feral cats. Several studies have shown that owners of dogs with S intermedius infections were also colonized by the organism. S intermedius infections in people are rare, but methicillin-resistant S aureus (MRSA) in dogs poses more of a threat to owners. Once thought uncommon, MRSA infection in both dogs and cats in the United States and the United Kingdom is increasing, and transfer among people, pets, and veterinary staff can occur. In one study, 18% of 78 staff members were found to be carriers of MRSA. Typing has shown that people are the source of the MRSA in dogs and cats. It is now apparent that pets can pose a risk for infection to owners and veterinary personnel and that human carriers of MRSA can present a risk for infection to animals in their care.

COMMENTARY: Most interesting in this review is the point about colonization of pet owners and veterinary staff by S intermedius or MRSA. Pets with chronic skin disease logically pose the most risk for being the point of origin for colonization. On the basis of the information presented, it seems reasonable to take measures to minimize colonization. Owners can increase bathing of pets with chronic skin conditions; wash their hands frequently; change clothing after bathing or grooming their pets; and regularly launder pet beds, collars, and leashes. Veterinary staff can be more attentive to hand and clothing hygiene as well. Technicians and staff should change laboratory coats or smocks daily, especially after handling pets with skin disease. A recent study of 42 neckties worn by physicians revealed that 20 were contaminated by microorganisms, including 12 S aureus isolates. Other items cultured included stethoscopes, pens, and penlights. Maybe it is time to have a staff meeting about banning neckties! -- Karen A. Moriello, DVM, Diplomate ACVD

Reservoirs of antimicrobial resistance in pet animals. Lloyd DH. CLIN INFECT DIS 45:S148-S152, 2007.