Methicillin-resistant Staphylococcus aureus (MRSA) is a type of staph bacteria resistant to many common antibiotics, including methicillin, penicillin, and amoxicillin. This resistance limits treatment options when the bacteria actively cause illness. Whether MRSA stays in the body forever depends on distinguishing between two states: an active infection and simply carrying the bacteria (colonization). Understanding this difference addresses the persistence of MRSA.
Infection Versus Colonization
MRSA infection occurs when the bacteria invade and actively cause illness, such as a painful skin boil, pneumonia, or a bloodstream infection. This state is temporary and requires specific medical treatment with antibiotics effective against the resistant strain. Active infection is treated and cleared, meaning the acute illness does not persist indefinitely.
MRSA colonization, or the MRSA carrier state, is when the bacteria are present on the body without causing symptoms or illness. The bacteria live on body surfaces and multiply without invading tissues or triggering an immune response. Approximately 2 in every 100 people carry MRSA, and many more carry the non-resistant S. aureus in their nose. This silent presence leads to the perception that the bacteria might be permanent.
Understanding the MRSA Carrier State
The MRSA carrier state explains the long-term persistence associated with the bacteria. Colonization most commonly occurs in the anterior nares (nostrils), which serve as the primary reservoir for the bacteria. MRSA can also reside on the skin, particularly in moist areas like the armpits, groin, throat, and skin folds. Presence in these sites is often asymptomatic and does not require treatment in a healthy individual.
Colonization carries two significant risks. A colonized person can unknowingly transmit the bacteria to others, which is a major concern in healthcare settings. Also, a carrier is at a higher risk of developing an active MRSA infection, especially if they have a surgical wound, a weakened immune system, or an indwelling medical device. Strategies to eliminate the carrier state are implemented because colonizing strains often match those that later cause infection in the same person.
Strategies for Decontamination
Eradication of the MRSA carrier state is attempted through decolonization, which uses antimicrobial agents to eliminate the bacteria from body surfaces. The common protocol involves topical treatments targeting primary colonization sites. Nasal decolonization uses a topical antibiotic ointment, such as 2% mupirocin, applied inside the nostrils twice daily for five to ten days. This treatment clears the bacteria from their main reservoir in the nose.
Simultaneously, a person may use an antiseptic body wash, such as chlorhexidine gluconate (CHG), for daily bathing over a similar time frame. CHG body washes work by binding to the bacterial cell membrane, which helps reduce the MRSA burden on the skin. These comprehensive decolonization regimens are highly effective, achieving success rates of up to 87–98% when the full treatment course is completed. For individuals with persistent colonization or recurrent infections, specialized treatment may be needed, including screening multiple body sites or using oral antibiotics combined with topical agents.
Monitoring and Preventing Recurrence
After decolonization, follow-up screening is performed to confirm MRSA has been cleared from the body. Monitoring involves swabbing previously colonized sites, such as the nose, a few days after the final treatment dose. The goal is to reduce the risk of future infection or transmission, which decolonization achieves.
MRSA is common in the environment, and a successfully decolonized person can become colonized again. The risk of re-colonization is addressed through rigorous personal hygiene measures. Preventative measures include frequent hand washing with soap and water, using alcohol-based hand sanitizers, and avoiding the sharing of personal items like towels and razors. For individuals with recurrent MRSA infections, a healthcare provider might recommend periodic courses of nasal mupirocin application to maintain a reduced carrier state.