Risk factors for meticillin-resistant Staphylococcus aureus (MRSA) carriage in MRSA-exposed household pets

Background: Household pets can carry meticillin-resistant Staphylococcus aureus (MRSA) introduced to the home by their human companions. Specific factors promoting pet carriage of this pathogen have not been fully elucidated. Objective: This study evaluated MRSA cultured from pets and the home environment in households where a human infected with MRSA had been identified, and aimed to determine potential risk factors for pet MRSA carriage. Materials and Methods: Humans diagnosed with community-associated MRSA (CA-MRSA) skin or soft-tissue infection (SSTI) in the mid-Atlantic United States were identified. One hundred forty-two dogs and cats from 57 affected households were identified of which 134 (94.4%) pets and the household environment were sampled for bacterial culture, PCR confirmation and spa-typing for MRSA strain determination. Samples were obtained 3 months later from 86 pets. Results: At baseline, 12 (9.0%) pets carried MRSA. Potential risk factors associated with carriage included pet bed (environmental) MRSA contamination, flea infestation and prior antimicrobial use in the pet. Pets tended to carry human-adapted MRSA strains and spa-types of MRSA isolates cultured from pets were concordant with strains cultured from the home environment in seven of eight homes (87.5%) at baseline. Conclusions and Clinical Relevance: Results may inform risk-based veterinary clinical recommendations and provide evidence for selective pet testing as a possible alternative to early removal of pets from the homes of humans infected with MRSA. MRSA contamination of the home environment is likely an important risk factor for pet MRSA carriage, and household interventions should be considered to reduce risk of MRSA carriage in exposed pets.