When drugs don't kill 'bugs': strategies for preventing the spread of infections caused by antibiotic-resistant bacteria - Feature Article

Nursing Homes, May, 2003 by Robert J. Sharbaugh

When Sir Alexander Fleming observed in 1928 that colonies of the bacterium Staphylococcus aureus could be destroyed by the mold Penicillium notatum, a new age was about to dawn--an age in which physicians would finally have effective weapons to use in their fight against infectious diseases. Many wounded and sick soldiers' lives were saved during World War II by penicillin, the antibiotic that was developed in 1941 from Fleming's discovery. Baby boomers and their parents have been routinely treated with this "miracle drug" ever since--and with the other antibiotics that followed.

We've all heard that too much of a good thing is not really so good. Over the last half-century, the wide use--and, in some cases, overuse--of antibiotics has caused many bacteria to develop resistance to the effects of these drugs. By the early 1960s, strains of antibiotic-resistant microorganisms (AROs) already were being identified. Pharmaceutical researchers have countered antibiotic resistance through the years by developing new agents to treat the infections caused by drugresistant bacteria. But the problem of resistance continues--to the point where, today, some infections are virtually untreatable with antibiotics. Needless to say this is a major public-health concern.

The good news for long-term care facilities is that some of the most highly drug-resistant bacteria are generally confined to other settings--for example, multiple-drug-resistant tuberculosis is found in prisons and in HIV-positive or homeless populations.

The bad news for long-term care is that other antibiotic-resistant bacteria exist throughout the general population and are being seen more and more often in LTC facilities. These include methicillin-resistant S aureus (MRSA) and vancomycin-resistant enterococci (VRE), as well as strains of Streptococcus pneumoniae, pseudomonas species, Neisseria gonorrhea, salmonella species, and others.

What can be done to protect LTG residents from being infected with these drug-resistant bacteria? When residents are admitted to a nursing home or assisted living residence directly from a hospital, could they already be infected with drug-resistant bacteria? Or might these new residents be carriers, bringing the microorganisms into the facility even though they themselves haven't developed an infection? This article will address these questions with infection-control strategies aimed specifically at the problem of antibiotic resistance, with particular attention being given to MRSA.

In general, the staphylococci, including S aureus, are common members of the human microflora and can routinely be found on theskin, in the oropharynx, and in the lower colon. S aureus causes many infectious complications, including wound infections, carbuncles, cystitis, food poisoning, pneumonia, bacteremia, endocarditis, and osteomyelitis. The vast majority of strains of S aureus are susceptible to many antibiotics, including methicillin. However, certain of the staphylococci, called coagulase-negative strains, are notoriously resistant to many antibiotics, including methicillin, a semisynthetic penicillin developed to treat penicillin-resistant bacteria. Fortunately, these strains are much less frequently involved as infectious agents, although they can sometimes cause surgical-site infections, infected prostheses, and bacteremias associated with in-dwelling vascular catheters, especially central lines. It is important to remember that resistance to methidillin also implies resistance to two other semisyn thetic penidillins: oxacillin and nafcillin.

MRSA is not new to the United States, having first been reported in the early 1970s. While its initial presence was noted primarily in VA hospitals and large teaching hospitals, it has, over the years, become widespread in nursing homes and in communities-at-large throughout the country and the world. Its presence, then, is certainly not restricted to the hospital, or nosocomial, setting.

In spite of its ubiquity, MRSA has not been found to be any more virulent than methicillin-sensitive strains of this organism. There are, however, some high-risk factors that tend to predispose one to infection with MRSA and other ARCs. Such factors would include respiratory complications (e.g., chronic obstructive pulmonary disease, pulmonary edema, and emphysema), open wounds, and invasive devices (e.g., central lines or tracheostomies). MRSA also tends to have a predilection for intravenous drug abusers and for patients who receive prolonged antibiotic therapy, especially with cephalosporins.

The staphylococci, including MRSA, are transmitted primarily through direct contact with the hands of healthcare providers. As a result, hand washing and the use of appropriate barrier precautions (e.g., gloves) are paramount in preventing the spread of this and other microorganisms. Hand washing is especially important after having contact with a resident's intact skin (e.g., when taking a pulse, or blood pressure or lifting a resident), before inserting in-dwelling urinary catheters or other invasive devices, and after contact with body fluids or excretions, mucous membranes, non-intact skin, and wound dressings.