To the Editor—Methicillin-resistant Staphylococcus aureus (MRSA) is a common nosocomial infectious agent with greater associated mortality and morbidity than infections caused by methicillin-susceptible Staphylococcus aureus isolates.Reference Gould ¹ One considerable reservoir of MRSA is patients in long-term care facilities, who often have >1 factor predisposing them to become persistent MRSA carriers: advanced age, prior hospitalizations with greater length of stay, the presence of wounds, indwelling devices, and chronic diseases.Reference Lucet, Chevret, Durand-Zaleski, Chastang and Régnier ² These patients have also been shown to have low rates of successful MRSA decolonization, and this report suggests that complex continuing care patients are similar.Reference Lucet, Chevret, Durand-Zaleski, Chastang and Régnier ^{2 –} Reference Shenoy, Paras, Noubary, Walensky and Hooper ⁴

There are several methods of MRSA management, none of which are universally established: topical or systemic decolonization,Reference Vanderhelst, De Wachter, Willekens, Piérard, Vincken and Malfroot ⁵ the implementation of isolation precautions, and follow-up screening.Reference Marschall and Mühlemann ^{3 ,} Reference Annex ⁶ Herein, we briefly describe a MRSA outbreak that occurred among long-term patients in a complex continuing care center from October 2013 through to December 2014 and the challenges concerning MRSA follow-up and management.

Patients were screened (ie, pooled swabs of axilla, nares, groin and perineum, and single swabs of all wounds and indwelling devices) upon admission or readmission to the facility. Colonized patients were on contact precautions per standard recommendations.Reference Annex ⁶ MRSA-positive patients who had no wounds or indwelling devices received topical decolonization with 2% mupirocin and 2% chlorhexidine gluconate. In addition, 1 patient also received systemic decolonization (ie, doxycycline, rifampin, chlorhexidine gluconate, and mupirocin) once. Decolonization was attempted no more than twice for any patient. Those not suitable for decolonization received daily baths with chlorhexidine gluconate. Pulsed-field gel electrophoresis was used to determine the relatedness of MRSA isolates.Reference Tenover, Arbeit and Goering ⁷

During this outbreak, 8 patients acquired MRSA, and 5 were previously colonized. A total of 5 unsuccessful topical decolonization attempts were made with 3 patients: 2 patients received decolonization twice, and a third patient received decolonization only once because previous failed attempts confirmed that our patients would not likely be decolonized using topical treatments.Reference Lucet, Chevret, Durand-Zaleski, Chastang and Régnier ^{2 –} Reference Shenoy, Paras, Noubary, Walensky and Hooper ⁴ In 1 previously positive case, a patient had acquired CMRSA-2 in July 2006 and systemic decolonization was attempted 1 month later. This patient tested positive for recolonization in July of 2009 after 463 days and 8 negative cultures. The patient subsequently tested negative 13 times over a period of 1,169 days before recolonizing again in January 2013. Thereafter, 2 negative culture times were observed, 1 involving 7 negative cultures over 127 days where the patient remained off precautions from April to December 2013, and the other involving 4 negative cultures over 56 days. Ultimately, the patient screened positive for MRSA again in April 2014. During the last negative surveillance period, the patient was not on precautions (March and April 2014). All isolates identified within this patient were >95% homologous (Figure 1a). A second previously positive patient originally tested positive for CMRSA-2 in March 2012. This patient subsequently cultured negative on 25 successive occasions over the course of 631 days and was not on precautions until screening positive for CMRSA-2 in April 2014. These isolates were indistinguishable by pulsed-field gel electrophoresis before and after a negative culture period of 631 days (Figure 1b).

FIGURE 1 Molecular characterization by pulsed-field gel electrophoresis of methicillin-resistant Staphylococcus aureus (MRSA) chromosomal DNA restriction fragments of isolates from patients colonized over extended periods of time.

Despite following recommended best practices,Reference Annex ⁶ this outbreak was triggered by previously positive patients who intermittently screened negative for MRSA and, therefore, were not always on contact precautions. Long durations of intermittent colonization with a single MRSA isolate were observed in these patients (Figure 1), which has been noted in other studies, the longest being 51 months.Reference Marschall and Mühlemann ³ These findings indicate either low levels of colonization where MRSA is present yet undetectable by regular culture methods, or intermittent shedding of MRSA.

A key challenge is the duration of MRSA colonization; 3 complex continuing care patients remained colonized for years, and 1 patient was colonized as long as 7 years and 9 months. The longest length of colonization previously observed in any group of patients was 5.56 years, with a median follow up of 940 days.Reference Larsson, Gustafsson, Nilsson, Odenholt, Ringberg and Melander ⁸ These patients are potential MRSA reservoirs and can remain on contact precautions receiving chlorhexidine gluconate baths for years. Patients on precautions utilize limited resources, such as single rooms.Reference Annex ⁶ Although the colonized patients in this report were in single rooms, there may be benefits in cohorting carriers. Cohorting may free single rooms for other needs and may alleviate certain psychological effects (ie, increased anxiety, depression, loneliness and adverse events) as well as limited healthcare worker contact, which can be issues for patients on precautions.Reference Annex ^{6 ,} Reference Abad, Fearday and Safdar ⁹ Systemic decolonization may also be considered in place of topical decolonization, which may reduce contact precautions whereby patients can screen negative by typical culture methods for months. However, no standard protocols exist, and there may be adverse effects with systemic decolonization that would not occur with topical methods.Reference Vanderhelst, De Wachter, Willekens, Piérard, Vincken and Malfroot ^{5 ,} Reference Annex ^{6 ,} Reference Chase, Webster and Materniak ¹⁰ Systemic decolonization would necessitate increased surveillance frequency to avoid undetected periods of intermittent shedding. There remains a paucity of data in support of systemic decolonization, as many studies involve varied patient groups, small sample sizes, and a lack of data to support the significant effectiveness of systemic decolonization over topical decolonization after a year.Reference Vanderhelst, De Wachter, Willekens, Piérard, Vincken and Malfroot ^{5 ,} Reference Larsson, Gustafsson, Nilsson, Odenholt, Ringberg and Melander ^{8 ,} Reference Chase, Webster and Materniak ¹⁰ Consideration of systemic methods of decolonization should be considered, as this patient population will likely remain in complex continuing care as chronic carriers.