Community-Associated Methicillin-Resistant Staphylococcus Aureus in Outpatients, United States, 1999-2006

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has become a major problem in U.S. hospitals already dealing with high levels of hospital-associated MRSA (HA-MRSA).

Using antimicrobial drug susceptibility data for 1999–2006 from The Surveillance Network, the authors characterized the relationship between outpatient and inpatient levels of CA-MRSA nationally. In outpatients, the frequency of CA-MRSA isolates has increased more than seven times during 1999–2006, which suggests that outpatients have become a major reservoir for CA-MRSA. However, contrary to results in other reports, although CA-MRSA increases are associated with decreases in the frequency of HA-MRSA in hospitals, the decreases are only modest. This finding suggests that instead of replacing HA-MRSA in the hospital, CA-MRSA is adding to the overall presence of MRSA already found within the hospital population.

The findings from this study have implications for local and national policies aimed at containing and preventing MRSA. More rapid diagnostic methods are urgently needed to better aid physicians in determining appropriate empiric therapy. Strategies for prevention of infection and treatment of patients with CA-MRSA within health care settings should be coordinated primarily at the local level in accordance with local susceptibility profiles. Lastly, infection control policies should take into account the role that outpatients likely play in the spread of MRSA and promote interventions that could prevent spread of MRSA from outpatient areas to inpatient areas.