Staphylococcus aureus is a major cause of healthcare-associated infection. An estimated 400,000 cases of S. aureus infection occurred in US hospitals in 2003. Approximately 60% of S. aureus hospital infections are caused by methicillin-resistant S. aureus (MRSA). It is estimated that MRSA infections are responsible for the death of nearly 19,000 hospitalized American patients annually. While S. aureus is known to colonize various anatomic sites, its primary habitat is the epithelium of the anterior nares. Therefore, active screening for MRSA using nasal swab culture followed by contact isolation of carriers is a widely practiced infection control strategy in US hospitals to prevent cross-transmission of this organism between patients. The advent of community-associated MRSA (CA-MRSA) strains, which are defined by distinct genetic traits and tendency to cause skin and soft tissue infection, is rapidly changing the epidemiology of MRSA. CA-MRSA strains, represented by the pulsed-field type (PFT) USA300 clone, may have a colonization pattern on the body surface that differs from healthcare- associated MRSA (HA-MRSA) strains. As the CA-MRSA epidemic progresses, CA-MRSA strains are increasingly becoming a common cause of healthcare-associated infections. In our preliminary study, we found that a substantial portion of patients who are colonized with MRSA are colonized on the skin, but not necessarily the nares. In addition, for some patients, we were able to recover MRSA using a sponge (which can sample a large area of the skin), but not swabs.
The specific aims addressed in this proposal are (1) to elucidate the colonization patterns of MRSA among patients in an acute care hospital and investigate the sensitivity of sponge-based screening method, and (2) to identify the difference in colonization patterns of CA- and HA-MRSA strains by determining the genotypes of the strains colonizing various anatomic sites. The main objective of this pilot is to develop a sensitive screening method for MRSA colonization. Such a method will then serve as a useful tool in studying the dynamics of MRSA colonization and evaluating the efficacy of infection control practices such as decolonization of carriers.
Methicillin-resistant S. aureus (MRSA) is a major cause of healthcare-associated infection in the United States. In many hospitals, whether a patient carries MRSA or not is determined by culturing of the nose. The proposed study aims to identify whether there are anatomic sites that are more sensitive in detecting MRSA than the nose, and whether the use of sponge enhances detection of MRSA.