Cluster of methicillin-resistantStaphylococcus aureuscolonization in a small animal intensive care unit

Abstract

Methicillin-resistant Staphylococcus aureus (MRSA) was isolated from the tracheostomy tube of an 18-month-old castrated male Golden Retriever in the intensive care unit (ICU) of the Ontario Veterinary College. This prompted an investigation of MRSA colonization in other animals in the ICU. On day 1 of the investigation, MRSA was isolated from nasal swabs obtained from 2 of 10 animals (2/7 dogs and 0/3 cats), including the index case. Subsequently, MRSA was isolated from 3 of 12 animals on day 9; 3 of 9 animals on day 13; and none of 14, 5, and 6 animals on day 20, 27, and 78, respectively. Overall, MRSA was isolated from 6 of 26 (23%) animals during the outbreak period (4/22 dogs and 2/4 cats). The apparent incidence of MRSA acquisition in the ICU from days 1 through 13 was 20% (5/25 animals). No clinical signs of MRSA infections developed. All isolates were indistinguishable from one another. Infection-control measures including active surveillance of all animals in the ICU, barrier precautions, and hand hygiene were used to control the apparent outbreak. Methicillin-resistant S aureus is an emerging problem in veterinary medicine. Intensive care units may be at particular risk for periodic outbreaks of colonization and disease. The outbreak of this report highlights the potential for clinically inapparent transmission of MRSA within a facility; infection-control measures that might facilitate MRSA eradication should be considered in ICU settings.