Control of Nosocomial Methicillin-Resistant Staphylococcus aureus Infection

To THE EDITOR—We write to express agreement with the statement of Klevens et al. [1] that, “regardless of which [methicillin-resistant Staphylococcus aureus (MRSA)] strains are present in hospitals, action is necessary to control further spread” (p. 391). We believe, however, that their next sentence, “Aggressive programs in several European countries have documented the success of identifying and treating colonized patients quickly,” (p. 391) misled readers by implying that health care facilities in those countries (and in Western Australia, which has had similar success with a similar approach [2]) quickly treat—but do not isolate—colonized patients, and that treating colonized patients is the key secret to those countries' success in controlling MRSA infection. On the contrary, Dutch eradication therapy is often postponed until conditions are optimal (frequently after discharge), whereas isolation is used for all patients with known or suspected MRSA colonization [3]. A recent Dutch study illustrated the importance of isolation, reporting that MRSA was transmitted to 38 individuals when 3 MRSA-colonized patients were admitted to an intensive care unit (ICU) unsuspected, uncultured, and unisolated, compared with transmission to only 1 individual when 3 other patients were suspected, cultures were performed, and the patients were isolated at admission to the same ICU [4]. Successes at the University of Virginia (Charlottesville) over 26 years, as well as at other American hospitals, confirm the importance of identifying and isolating all colonized patients [5–8], including many situations where eradication therapy was not used [5, 8–10]. Active detection and isolation have worked well for other contagious pathogens, such as smallpox virus [11], severe acute respiratory syndrome (SARS) coronavirus [11], Mycobacterium tuberculosis [12], and other antibiotic-resistant pathogens, such as vancomycin-resistant Enterococcus species, for which eradication therapy was not possible [13–16].

The Centers for Disease Control and Prevention (CDC) has never explicitly recommended routine use of active surveillance cultures for control of MRSA and vancomycin-resistant Enterococcus species; so only few US health care facilities have used them routinely to identify and isolate all colonized patients [17]. Standard precautions, as recommended by the CDC, have failed to stem the growing tide of MRSA infections in many settings [18], including in the CDC's National Nosocomial Infections Surveillance (NNIS) system hospitals [1], where standard precautions have been required since 1996 (including mandatory annual infection-control retraining of all health care workers). In 1983, the CDC began recommending that contact isolation of patients with known or suspected colonization or infection be used to control spread of epidemiologically important antibiotic-resistant pathogens like MRSA. Data were already available at that time that suggested that success would require active surveillance cultures to identify and isolate all MRSA-colonized patients [5].

Eradication therapy to eliminate MRSA colonization can help control the spread of infection, because an individual who is no longer a carrier is no longer a reservoir for spread [3, 19, 20]; however, the very high MRSA prevalence in many US health care facilities would make it difficult to use eradication therapy for primary control of infection (i.e., for logistical reasons, and because of the potentiation of mupirocin resistance). Because active detection and isolation of all colonized patients results in major reductions in rates of infection, even in hospitals with very high levels of endemicity and without the use of eradication therapy [5, 9, 10], this practice should remain as the mainstay [21]. After MRSA prevalence falls, eradication therapy could then be added judiciously, making its use safe and convenient.