Methicillin-Resistant Staph Aureus
The Rise of a Multi-Drug Resistant Bacterium in Two Settings
MRSA is becoming a major health issue in the hospital and the community. What exactly is this infectious pathogen?
Staphylococcus aureus is a bacterium that is both harmless as a ubiquitous bacterium and dangerous as a pathogen. It is found virtually everywhere, even on people's skin. But once introduced into soft tissues under the skin, the bloodstream, or any other part of the body that is normally sterile, there is the potential for infection. To make matters worse, a resistant form of this bacterium called methicillin-resistant Staphylococcus aureus (MRSA) has been on the rise.
Hospital-Acquired and Community-Acquired MRSA
As with most resistant pathogens, MRSA appeared because of frequent use of antibiotics. Although the name states that the bacterium is specifically resistant to methicillin, the resistance actually includes multiple drugs of the penicillin and cephalosporin classes of antibiotics. In the beginning, MRSA was limited to inhabiting the hospital setting, so people would be infected with MRSA as a hospital-acquired, or nosocomial, infection (HA-MRSA) through unsanitary contact transmission.
In contrast, community-acquired MRSA (CA-MRSA) is contracted anywhere outside the hospital. It is particularly true in close-contact settings, like prisons, child day care centers, and sports teams. Other risk factors may play a role, such as breaks in the skin and sharing items. Like HA-MRSA, CA-MRSA is resistant to multiple drugs. However, CA-MRSA has slightly different mechanisms for resistance, suggesting that it truly originated in the community and is not simply HA-MRSA brought into the community.
However, the line dividing these two designations is often blurred. People may get MRSA from the hospital and develop an infection upon entering the community, and vice versa. This is evident because of cases where strains unique to one of the two settings are found in the other setting. The lesson here is that MRSA infection, traditionally limited to hospitals, can occur anywhere.
Management of Infections
Whether it is MRSA or methicillin-sensitive Staphylococcus aureus (MSSA), the bacterium can cause many types of infections, including but not limited to cellulitis, pneumonia, wound infections, endocarditis, and sepsis. Even with resistance to several antibiotics, there are still other antibiotic regimens to use for treatment, including the antibiotic vancomycin. Gram stain and culture to characterize the bacterium itself can also help, in case MSSA is involved and not MRSA. But regardless of the setting, hygiene is a key element in prevention.
The Future
As MRSA continues to be a challenge for healthcare professionals, experts will continue to monitor statistics related to this pathogen. Besides the greater prevalence of MRSA, there is also the concern of further antibiotic resistance, especially with use of vancomycin. Only time will tell the direction that current trends will ultimately take.
References
- Boyce, John M. "Epidemiology of Methicillin-Resistant Staphylococcus Aureus Infection in Adults." UpToDate. Ed. Burton D. Rose. Waltham, MA: UpToDate, 2008.
- Boyce, John M. "Patient Information: Methicillin-Resistant Staphylococcus Aureus (MRSA)." UpToDate. Ed. Burton D. Rose. Waltham, MA: UpToDate, 2008.
