A 45-year-old previously healthy female was admitted to the ICU with sepsis caused by community-acquired pneumonia. Per hospital policy, all patients admitted to the ICU are screened for MRSA colonization. If the nasal screen is positive, contact isolation is initiated and the hospital’s MRSA decolonization protocol is implemented. Her nasal screen was positive for MRSA.
MRSA infections are associated with significant morbidity and mortality, and death occurs in almost 5% of patients who develop a MRSA infection. In 2005, invasive MRSA was responsible for approximately 278,000 hospitalizations and 19,000 deaths. MRSA is a common cause of healthcare-associated infections (HAIs) and is the most common pathogen in surgical site infections (SSIs) and ventilator-associated pneumonias. The cost of treating MRSA infections is substantial; in 2003, $14.5 billion was spent on MRSA-related hospitalizations.
It is well known that MRSA colonization is a risk factor for the subsequent development of a MRSA infection. This risk persists over time, and approximately 25% of individuals who are colonized with MRSA for more than one year will develop a late-onset MRSA infection.1 It is estimated that between 0.8% and 6% of people in the U.S. are asymptomatically colonized with MRSA.
One infection control strategy for reducing the transmission of MRSA among hospitalized patients involves screening for the presence of this organism and then placing colonized and/or infected patients in isolation; however, there is considerable controversy about which patients should be screened.
An additional element of many infection control strategies involves MRSA decolonization, but there is uncertainty about which patients benefit from it and significant variability in its reported success rates.2 Additionally, several studies have indicated that MRSA decolonization is only temporary and that patients become recolonized over time.
It is estimated that 10% to 20% of MRSA carriers will develop an infection while they are hospitalized. Furthermore, even after they have been discharged from the hospital, their risk for developing a MRSA infection persists.
Most patients who develop a MRSA infection have been colonized prior to infection, and these patients usually develop an infection caused by the same strain as the colonization. In view of this fact, a primary goal of decolonization is reducing the likelihood of “auto-infection.” Another goal of decolonization is reducing the transmission of MRSA to other patients.
In order to determine whether MRSA colonization is present, patients undergo screening, and specimens are collected from the nares using nasal swabs. Specimens from extranasal sites, such as the groin, are sometimes also obtained for screening. These screening tests are usually done with either cultures or polymerase chain reaction testing.
There is significant variability in the details of screening and decolonization protocols among different healthcare facilities. Typically, the screening test costs more than the agents used for decolonization. Partly for this reason, some facilities forego screening altogether, instead treating all patients with a decolonization regimen; however, there is concern that administering decolonizing medications to all patients would lead to the unnecessary treatment of large numbers of patients. Such widespread use of the decolonizing agents might promote the development of resistance to these medications.
Medications. Decolonization typically involves the use of a topical antibiotic, most commonly mupirocin, which is applied to the nares. This may be used in conjunction with an oral antimicrobial agent. While the nares are the anatomical locations most commonly colonized by MRSA, extranasal colonization occurs in 50% of those who are nasally colonized.