Methicillin-resistant Staphylococcus aureus (MRSA) is a type of bacteria resistant to several common antibiotics, including methicillin. It is important to distinguish between an active MRSA infection, where the bacteria causes illness, and MRSA colonization, where it lives on the body without causing harm. While many individuals carry non-resistant Staphylococcus aureus without issue, carriage of the resistant MRSA strain carries an elevated risk that warrants treatment. The process of eliminating this harmless colonization is known as decolonization.
Why Nasal MRSA Carriage Matters
The anterior nares (inside of the nostrils) serve as the primary reservoir for Staphylococcus aureus and MRSA. Bacteria in this passage can easily spread to the skin and other parts of the body via the hands, making the nose a continuous source of potential contamination.
Nasal carriage significantly increases the risk of developing an invasive MRSA infection, where the bacteria enters the bloodstream or deep tissue. This risk is pronounced for patients in high-risk settings, such as those preparing for major surgery, or those with medical devices like catheters. Patients colonized with MRSA are approximately four times more likely to develop an invasive infection compared to those carrying the non-resistant strain. Decolonization aims to eliminate this nasal reservoir, reducing the chances of the bacteria causing serious illness.
Primary Medical Decolonization Treatments
The most common prescription agent used to eliminate MRSA from the nose is Mupirocin, typically a 2% nasal ointment. Mupirocin is a topical antibiotic that works by inhibiting the bacterial enzyme isoleucyl-tRNA synthetase. Blocking this enzyme halts the synthesis of bacterial proteins, which ultimately kills the MRSA cells.
The ointment is applied directly inside the anterior nares to target the bacteria at their colonization site. Mupirocin has historically been highly effective, often eradicating the bacteria in most treated patients. Alternative agents, such as povidone-iodine preparations, are sometimes used, particularly if Mupirocin resistance is suspected. Povidone-iodine is a broad-spectrum antiseptic that rapidly kills bacteria on contact and is often preferred for short-term suppression, such as before a surgical procedure.
Understanding the Decolonization Protocol
A typical MRSA decolonization regimen focuses on eliminating reservoirs in both the nose and the rest of the body. The standard nasal treatment duration is five days, with Mupirocin ointment applied twice daily to the inside of each nostril. A small amount is applied, and the nostrils are pinched together to distribute the ointment throughout the nasal passage.
This nasal treatment is combined with antiseptic body washing, most commonly using a 2% or 4% chlorhexidine gluconate (CHG) solution. The CHG body wash is used daily for the same five-day period to remove MRSA from the skin and body folds. Strict adherence to this dual protocol is important, as failure to treat extra-nasal sites can lead to rapid recolonization.
Managing Treatment Failure and Resistance
The primary limitation to the use of Mupirocin is the growing problem of bacterial resistance. Increased use makes MRSA strains more likely to develop mechanisms to circumvent its effects, such as high-level resistance mediated by the mupA gene, which is associated with decolonization failure.
Healthcare providers limit Mupirocin use to necessary protocols to preserve its effectiveness. If initial decolonization fails, doctors may repeat the nasal treatment with an alternative agent, such as povidone-iodine. In rare, high-risk cases, systemic antibiotics may be considered as a last resort, though this approach carries risks. Ongoing screening and monitoring are necessary to confirm successful decolonization and detect any potential return of MRSA carriage.