Resistance mechanisms are employed by bacterial organisms to gain a growth advantage in conditions that impose a tremendous selective pressure, resulting in the materialization of isolates that are resistant to multiple classes of antimicrobials. Surveillance systems are commonly used in human medicine to track the frequency and emergence of these strains, and this information is used to implement infection control policies aimed at reducing the number of these organisms. The implementation and sophistication of these monitoring programs in veterinary medicine lags behind the human counterpart. With the increasing prevalence of methicillin-resistant Staphyloccus aureus (MRSA) in humans, particular emphasis is placed on methicillin-resistant staphylocci (MRS) at the OSU-VMC. All staphylococcal species isolated during routine microbiological examination are screened for the presence of the mecA gene, which defines an isolate as being methicillin-resistant. This gene is carried on the Staphylococcal Cassette Chromosome (SCCmec), which can be used to help further classify MRS organisms. Healthcare-associated methicillin-resistant Staphylococcus aureus (HA-MRSA) is typically isolated from patients in a healthcare setting, tends to be multidrug resistant, and is usually associated with SCCmec types I, II, or III. Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) is typically isolated from young, healthy individuals with no history of indwelling medical devices, recent visitation to a healthcare facility, or any other risk factors for HA-MRSA. CA-MRSA is usually associated with skin and soft tissue infections, is generally susceptible to multiple antimicrobial classes, contains the Panton-valentine leukocidin (PVL) gene, and is most often associated with SCCmec types IV, V, VI, and VII. Additionally, using DNA fingerprinting methods, HA-MRSA strains are generally most related to USA types 100, 500, and 800, while CA-MRSA are most related to USA types 300 and 400. Bidirectional transmission facilitates the zoonotic potential of these organisms. Unlike human medicine, long term veterinary studies are lacking, so little information is available to determine how the prevalence of MRSA and MRSP have changed over time. However, the availability of DNA fingerprinting methods such as PFGE have facilitated efforts to determine if isolates from separate sources are clonally related; these results provide information that can be used to better characterize how MRSA and MRSP are being transmitted between humans, animals, and the environment. Our study will provide information on prevalence, including changes over time and will provide information that can be used to track the movement of pathogens among and between patients within the veterinary medical center. This information can be used to guide the judicious use of antimicrobials and to implement infection control procedures aimed at limiting the spread of pathogens between animals, the hospital environment, hospital staff, and owners.
The main objectives of this project are:
Determine if antimicrobial prescribing practices provide selective pressure for multidrug resistant organisms
Determine the prevalence of MRSA and the level of clonality among these species
Identify novel genotypes