Post-Discharge Methicillin-Resistant Staphylococcus aureus Infections: Epidemiology and Potential Approaches to Control

Development of Strategies to Decrease Post-Discharge MRSA

While the epidemiology of post-discharge health care–associated MRSA infections has become a topic of interest to researchers, approaches to control are in their infancy. Few of the approaches have been subjected to rigorous study in the post-discharge environment. Nevertheless, some low risk, common sense strategies may be considered. Furthermore, an outline of research objectives may be constructed.

Prevention of Colonization in the Inpatient Setting

Robust infection control measures must be implemented in inpatient settings to prevent incident MRSA colonization [16,17]. Key recommendations include surveillance and monitoring of MRSA infections, adherence to standard hand hygiene guidance, environmental cleanliness, and use of dedicated equipment for patients who are colonized or infected with MRSA. Active screening for asymptomatic MRSA carriage and isolation of carriers may be implemented if routine measures are not successful.

Decolonization

Despite the best infection control programs, some patients will be colonized with MRSA at the time of hospital discharge. As detailed above, MRSA colonization is a potent risk factor for infection in the post-discharge setting, as well as in hospital inpatients [22]. A logical approach to this would be to attempt to eradicate colonization. There are several strategies for decolonization therapy, which may be used alone or in combination, including nasal mupirocin, nasal povidone-iodine, systemic antistaphylococcal drugs alone or in combination with oral rifampin, chlorhexidine bathing, or bleach baths [26–29].

A preliminary step in approaching the idea of post-discharge decolonization therapy is to show that patients can be successfully decolonized. With those data in hand, randomized trials seeking to demonstrate a decrease in invasive MRSA infections can be planned. Decolonization using nasal mupirocin has an initial success rate of 60% to 100% in a variety of patient populations [30–35]. Poor adherence to the decolonization protocol may limit success in the outpatient setting. Patients are more likely to resolve their MRSA colonization spontaneously when they regain their general health and independence in activities of daily living [23]. Colonization of other household members may provide a reservoir of MRSA leading to recolonization of the index case. Treatment of the household members may be offered, to provide more durable maintenance of the decolonized state [35]. When chronically ill patients who have been decolonized are followed longitudinally, up to 39% become colonized again, most often with the same strain [30,31]. Attempts to maintain a MRSA-free state in nursing home residents using prolonged mupirocin therapy resulted in emergence of mupirocin resistance [31]. Thus decolonization can be achieved, but is difficult to maintain, especially in debilitated, chronically ill patients. Mupirocin resistance can occur, limiting success of decolonization therapies.

Successful decolonization has been proven to reduce the risk of MRSA infection in the perioperative, dialysis, and intensive care unit settings [33,36–38]. In dialysis patients the risk of S. aureus bloodstream infection, including MRSA, can be reduced 59% with the use of mupirocin decolonization of the nares, with or without treatment of dialysis access exit sites [37]. A placebo-controlled trial demonstrated that decolonization of the nares with mupirocin reduced surgical site infections with S. aureus. All S. aureus isolates in the study were methicillin-susceptible. A second randomized controlled trial of nasal mupirocin did not achieve a statistically significant decrease in S. aureus surgical site infections, but it showed that mupirocin decolonization therapy decreased nosocomial S. aureus infections among nasal carriers [33]. 99.2% of isolates in that study et al were methicillin-susceptible. Quasi-experimental studies have shown similar benefits for surgical patients who are colonized with MRSA [39–41]. A more recent randomized trial, in ICU patients, demonstrated decreased incidence of invasive infection in patients treated with nasal mupirocin and chlorhexidine baths [38]. The common themeof these studies is that they enrolled patients who had a short-term condition, eg, surgery or critical illness, placing them at high risk for invasive MRSA infection. This maximizes the potential benefit of decolonization and minimizes the risk of emergence of resistance. Furthermore, adherence to decolonization protocols is likely to be high in the perioperative and ICU settings. To extrapolate the ICU and perioperative data to the post-discharge setting would be imprudent.