Methicillin-resistant
Staphylococcus aureus

(MRSA)

Methicillin-resistant Staphylococcus aureus (MRSA) is a bacterium that causes various types of infections.  Due to its increased resistance to certain antibiotics, MRSA infections have become more difficult to treat.  MRSA is spread person-to-person through direct contact.

MRSA is most common among those with lowered immunity and have a history of hospitalization, recent medical procedure, or nursing home residency.  Studies have shown that nosocomial or healthcare-associated (HA)-MRSA infection is on the rise.  In intensive care units (ICUs) at hospitals participating in the National Healthcare Safety Network (NHSN), the mean percentage of S. aureus isolates that were MRSA increased from 2.4% in 1975 to 29% in 1991 and to 51.3% in 2002.¹ 

In addition to this increase in healthcare settings, MRSA is emerging as an important pathogen in the community as well.  MRSA infections that occur in healthy individuals who have not been recently (within the past year) hospitalized or had a medical procedure (such as dialysis, surgery, catheters) are known as community-associated (CA)-MRSA infections.

Although healthcare and community MRSA appear distinct in their clinical, microbiologic, and genetic characteristics, the surveillance activities for both are integrated. 

Surveillance for MRSA has traditionally been performed in hospitals and other healthcare settings, and rates calculated among patients at single institutions.¹ However, with the emergence of MRSA as a community pathogen, there is now a rationale for performing surveillance on a community-wide basis, so that population-based rates of disease can be determined.

For more information on MRSA, please visit the following CDC websites: CDC HA-MRSA Site, CDC CA-MRSA Site, The National MRSA Education Initiative

1. Panlilio AL, Culver DH, Gaynes RP, Banerjee S, Henderson TS, Tolson JS, Martone WJ, National Nosocomial Infections Surveillance System. Methicillin-resistant Staphylococcus aureus in U.S. hospitals, 1975-1991

Image courtesy of the CDC Public Health Image Library

Maryland Emerging Infections Program/ABCs
Johns Hopkins University Bloomberg School of Public Health
Candler Building
111 Market Place, Suite 850, Room 8546
Baltimore, MD 21202
Phone: 410-223-1810
Fax:  410-223-1815
Email: mdabcs@jhsph.edu