Methicillin-resistant S. aureus infection is a particularly serious problem in hospitals, where MRSA often exceeds 25% of S. aureus isolates. Because MRSA strains are not susceptible to cephalosporin or semi-synthetic penicillin antibiotics, intravenous vancomycin is usually employed when MRSA infections occur. For reasons of cost, toxicity, and to avoid driving the emergence of vancomycin-resistant Enterococcus (VRE) or the more fearsome vancomycin-resistant S. aureus (VRSA), vancomycin is not routinely ordered at the outset of most infections. Rather, empiric antibiotics are selected that would usually treat the affected body system. A delay of 36-48 hours may occur before culture results identify MRSA and antibiotics are changed. Like all bacterial species, there are many strains of MRSA. Some posit that MRSA may be inherently more pathogenic than methicillin-sensitive S. aureus (MSSA), but the data are inconclusive.1 Also of note, some MRSA strains are susceptible to antibiotics other than vancomycin, and some of these can be given orally. Community-acquired MRSA strains may be more broadly susceptible, as shown in a recent study comparing community-acquired to hospital-acquired MRSA: ciprofloxacin 79% versus 16% susceptible; clindamycin 83% versus 21%; erythromycin 44% versus 9%; trimethoprim-sulfamethoxazole 95% versus 90%; and vancomycin, both 100%.2

To prevent the spread of MRSA between hospitalized patients, hospital epidemiologists recommend contact precautions for infected or colonized patients. Because MRSA colonization often persists for months or years, at our institution a “flag” is maintained in the patient’s record and precautions are immediately resumed if the patient returns to the hospital at a later time.

Presence of MRSA may delay or alter discharge plans. Many nursing homes also employ contact precautions for patients known to have recently carried MRSA. Patients with MRSA can be placed in rooms with other MRSA-positive patients (cohorting) or in private rooms, but staff members must still observe contact precautions such as using gloves for all contact and disposable gowns for more extensive care, adding cost and reducing efficiency. Consequently, finding post-hospital institutional placement for patients with MRSA may be difficult. The problem is compounded by a misunderstanding of “mersa” by staff members, patients, and family members. Methicillin-resistant S. aureus is perceived by some to be a mysterious and dangerous contagion rather than a variant strain of a bacterium that is commonly present on many individuals’ skin or inside their nares.

Given the prevalence and persistence of MRSA, presence of this bacterium poses a question for medical practitioners who work in outpatient environments such as the office or the home: should we follow contact precautions in these other settings? Often, MRSA-carrying patients appear in our offices or are seen on house calls within days or weeks of being discharged from hospitals, where we carefully donned gloves, used “dedicated” stethoscopes that stayed in the patients’ rooms, washed hands between patients with antiseptic soap, and avoided surface contact that could transfer microorganisms. Sitting on the bed of a patient with MRSA in a wound or VRE in his or her stool would not be compliant with contact precautions. Could we not see ourselves unwittingly sitting on the bed of such a patient in the home? The only real difference lies in the distance we travel between patients.

Intuitively, it seems unlikely that MRSA infection is being spread in an epidemic manner from one home care patient to the next by careless health care providers; cause-and-effect cases are difficult to recall. Yet, home health care workers usually have no way of knowing when acute illnesses that may have resulted from nosocomial contagion occur in their patients. It is thus worthwhile to review data that may help us quantify the risk and choose a plan of action.

Methicillin-resistant S. aureus is not very prevalent in the community among healthy individuals. In 1998, prevalence of S. aureus colonization in the general population of the United Kingdom was 23% and MRSA carriage rate was 1.5%.3 At Tripler Army Medical Center in Hawaii, 38% of asymptomatic outpatients carried S. aureus and 2% carried MRSA.4 In San Francisco’s urban poor population, 22.8% were colonized with S. aureus and 2.8% carried MRSA.5 

However, in patients with more disease and more health care exposure, MRSA carriage is more common. MRSA was found in 15% of elderly inpatients with prolonged hospital stays, and was associated with exposure to ampicillin or quinolone antibiotics.6  Records from hospitals in four Connecticut urban areas showed that 48% of S. aureus bacteremia episodes originated in the community; one-third involved MRSA and these always occurred in patients with underlying health problems.7 A recent case-control study similarly showed that MRSA bloodstream infections established at the time of hospital admission resulted from prior exposure to MRSA in a health care facility rather than the community.8 Among patients on French acute geriatric care wards, 14.6% were MRSA carriers, a state associated with prior hospitalization within 6 months and the presence of wounds.9 Additional evidence came from a study conducted in Detroit showing that MRSA strains were from many clones and tended to be found much more often in persons with recent stays in health care facilities.10 A large Canadian database showed that of 3009 MRSA cases with a known site of infection, 86% were acquired in hospitals, 8% in nursing facilities, and 6% in the community. Methicillin-resistant S. aureus infections most often involved skin or soft tissues (25%), lung (24%) or surgical sites (23%), and 13% were bacteremic.11 Similarly, among 1100 MRSA infections reported in Minnesota, 12% were community-acquired and 85% were health care-associated.2

Acquisition of MRSA during a hospital stay is more common among those who have prolonged admissions (17.7 days in patients acquiring MRSA vs 5.3 days in those who did not).12 Methicillin-resistant S. aureus is also common in long-term care facilities. In a chronic care facility, 125 of 519 individuals were MRSA-positive at some point, including 11.6% who were MRSA-positive on admission and 69 patients who acquired MRSA in the facility.13 In another nursing facility, MRSA was found in 6.2% of patients on surveillance culture.14 Careful analysis of MRSA strains also demonstrated that in one nursing home, five patients brought MRSA from the hospital, which then spread to 12 others.15 In group living settings, MRSA can cause serious epidemic outbreaks, especially if precautions are inadequate and antibiotics are often used.  In one institution, S. aureus was found in 60% of residents and 32% of staff members; of these, MRSA was found in 96% of residents and 26% of staff members’ cultures.16 This problem can be widespread in an institution. In 1998, 43% of one skilled care facility’s residents grew antibiotic-resistant bacteria, including MRSA (24%), resistant strains of Klebsiella pneumoniae (18%) and Escherichia coli (15%), and VRE (3.5%), yet only 3% were on contact precautions.17 In another study completed late in 2000, numerous patients from long-term care facilities admitted to hospitals carried resistant organisms: 16.3% of urine specimens, 6.7% of blood cultures, and 40% of sputum cultures.18

Perhaps because there are many persons in our communities who have chronic ill health or have spent time in hospitals, MRSA may be more widespread than we think, and health care workers may play an important role as vectors. A study in Charlottesville, VA, found MRSA colonization in 25 (14.5%) of 172 household and community contacts exposed to patients known to harbor MRSA.19 In another study involving a 600-bed French tertiary care hospital, 6.2% of health care workers carried MRSA, and several workers’ family members were also MRSA carriers.20 

Thus, based on this evidence, we should probably treat nursing home patients much like we do hospital patients, and although contagion with MRSA and other resistant pathogens during home care episodes is probably not a major public health problem, it is probably also far from rare. Providers in the field, whether in patients’ homes or in the office, should all follow basic hygienic procedures,21 all of which are too often overlooked even though they are Joint Commission on Accreditation of Healthcare Organizations (JCAHO) standards. The foremost is hand-washing between patient contacts using antiseptic soap (preferably one that contains chlorhexidine). To facilitate this, providers in our house calls program carry containers of antiseptic cleansing foam that is alcohol-based and requires no sink or towels. Also, do not reach into your doctor bag for equipment after examining a patient who may carry resistant bacteria, unless you plan to clean your hands or change your gloves first. For patients recently released from hospitals with open wounds or who are known to carry MRSA, it may be prudent for providers to wear gloves during direct contact and to avoid contaminating our clothes. When patients develop infections where S. aureus is a likely pathogen (skin, for example), high-risk patients should receive medication likely to inhibit MRSA, such as trimethoprim-sulfamethoxazole, clindamycin, or a quinolone, rather than a beta-lactam medication. Finally, when our informed judgment tells us it is safe enough, we should seek to retain vitally important features of the house call even in this modern era of frightful pathogens: sitting at the patient’s beside and providing a compassionate human touch.