MRSA Risk Factors and Incidence in Long-Term Care Facilities

Introduction: Nosocomial Infections and Vulnerable Populations

Nosocomial infections are a common occurrence in hospitalized patients, and such infections are often resistant to treatment. According to the Centers for Disease Control and Prevention, 70% of hospital-acquired bacterial infections in the United States — which kill 90,000 Americans a year — are resistant to at least one drug (Wenner, 2008, p. 11). Challenges to the immune system, open wounds, previous exposure to antimicrobial treatments, and open systems associated with treatment — such as chest tubes and, more commonly in long-term care facilities, Foley urinary catheters — all increase the opportunity to acquire one of the highly concentrated infectious diseases found on surfaces and in the air within institutions such as hospitals and long-term care facilities (LTCFs).

A particularly vulnerable human population is the elderly, as they often face additional physical challenges that further increase the incidence of opportunistic infections both in the community and in hospital settings. Long-term care facilities are also frequently populated by patients who require longer periods of recovery, physical and occupational therapy, dietary support, and assistance with activities of daily living than a short hospital stay can provide. These patients — often elderly — end up in LTCFs because their limited mobility and infirmity cannot be managed in a home setting. It is therefore reasonable to assume that such patients have a greater likelihood of transferring hospital-acquired infectious diseases into long-term care facilities, where those diseases may then spread to others.

Strausbaugh, Crossley, Nurse, and Thrupp suggest that in the LTC setting, person-to-person contact — particularly via healthcare workers' hands — is the most common means of transmission for these "superbugs," whether they enter through a colonized patient or develop into antibiotic-resistant strains within the LTCF itself. The same researchers stress that patients at greatest risk for MRSA colonization and other resistant bacteria are those with "serious underlying disease, poor functional status, wounds such as pressure sores, invasive devices such as urinary catheters, and prior antimicrobial therapy" (Strausbaugh, Crossley, Nurse & Thrupp, 1996, p. 129). Importantly, the researchers also note that many LTCFs lack adequate systems and procedures to eliminate these bacteria, and that there are cases where infections become aggressive and rapidly spread throughout the facility population, affecting both patients and higher-functioning staff (Strausbaugh et al., 1996, p. 129).

Staphylococcus aureus and several other infectious agents are a frequent occurrence in the LTC setting, and increasingly these agents are antibiotic resistant. The danger then becomes one of adaptive bacterial behavior: as diseases are treated with broad-spectrum antibiotics, only the weaker, non-adaptive strains are eradicated, leaving behind those increasingly capable of resisting known treatments. These resistant bacteria then colonize in the body where, not unlike a cancer, they move through the body's transport systems and manifest as traditional skin eruptions or, more seriously, attack deeper organ and bone systems — all while failing to respond to antimicrobial medications (Hughes & Andersson, 2001, p. 16). Colonized patients then experience near-constant outbreaks of the disease for the rest of their lives, or are eventually killed as the bacteria attacks vital functioning areas of the body. One of the most unpredictable and destructive of these superbugs is MRSA — methicillin-resistant Staphylococcus aureus — which frequently colonizes in patients and is resistant even to the strongest antibacterial treatments (Hughes & Andersson, 2001, p. 1).

Due to the high incidence of nosocomial infections in LTCFs, as well as antibiotic-resistant strains of bacteria — the most troubling of which is MRSA, given its unpredictability — LTCFs are in need of specialized research. MRSA can range from causing little more than a topical skin infection or showing no symptoms whatsoever, to systematically attacking vital systems of the body and resulting in serious illness or death. A further complication is that community-acquired MRSA (CA-MRSA) and historically known nosocomial strains are now intermingling in institutional settings and developing into even more resistant variants (Gorak, Yamada & Brown, 1999, pp. 797–800; Rutledge, 2007).

Statement of the Problem

LTCF residents also represent a practical research population: they are geographically concentrated, typically spend extended periods in facilities — unlike the high-turnover environment of hospitals and clinics — and are likely to consent to limited research aimed at improving their own outcomes and those of others. Despite this, only limited research has been conducted on this population. A great deal more could and should be done to decrease the odds of infection, further disease complications, and most importantly mortality from secondary infections such as MRSA.

Research Question: What is the incidence of MRSA in LTCF patients, and among these patients, who is at highest risk for infection and for spreading it?

Background and Significance of the Study

Statement of Purpose: Knowledge of the prevalence of MRSA colonization is important to controlling the spread of infection. Determining the prevalence of MRSA colonization among older residents in the LTC setting and identifying resident risk factors for colonization are of high priority in the development of both prophylactic and primary treatment strategies.

Bacteria have a natural capacity to adapt to treatment. As weak, non-adaptive strains are killed off by standard therapy, those that are adaptive survive and reproduce, becoming increasingly resistant to available treatments. When hosts deposit these adaptive bacteria on surfaces, in the air, or directly onto new hosts, the cycle repeats — and with each iteration, the emerging bacteria become more capable of resisting treatment.

Hughes and Andersson (2001) argue that if antibiotic treatment had never been introduced, bacteria would not have needed to adapt microbiologically to survive and might never have developed the capacity to resist treatment. In other words, they argue that resistance is largely a consequence of repeatedly exposing relatively benign bacteria to antibiotics when the human immune system might have been capable of defeating the infection naturally (p. 16). Had antibiotics been reserved strictly for life-threatening or permanently damaging infections, most would likely still be effective. As Hughes and Andersson put it: "There would be no need for bacteria to accumulate mutations or acquire extrachromosomal DNA specifying resistance mechanisms if it were not for the use of antibiotics" (p. 16).

The number of resistant bacterial strains continues to grow as bacteria do precisely what they are biologically programmed to do. Over-reliance on the so-called "miracles" of modern medicine — including the indiscriminate use of broad-spectrum antibiotics to treat non-life-threatening or even viral infections — has placed the global healthcare system in an increasingly threatened position. The World Health Organization has identified antimicrobial resistance as one of the greatest threats to global health, food security, and development, underscoring the urgency of research like the study proposed here.

Conclusion and Implications

LTC patients with risk factors including serious underlying disease, poor functional status, wounds such as pressure sores, invasive devices such as urinary catheters, and prior antimicrobial therapy (Strausbaugh, Crossley, Nurse & Thrupp, 1996, p. 129) will have a higher likelihood of disease conversion and colonization. Among patients without disease symptoms, colonization will be more prevalent than currently assumed, and preventative treatment may assist in isolating MRSA before it spreads epidemically to non-colonized patients.