Sheila Dunn, D.A. and Sarah E. Alholm, M.A.S.
This is the first in a series of Featured Articles that cover MRSA infections in the medical setting. In this article, contributing authors, Sheila Dunn, D.A. and Sarah Alholm, M.A.S., cover the basic facts about MRSA. Be sure to read the second article in the series: A Guide to MRSA Infections for Healthcare Workers: Part II - Preventing Transmission
Introduction
Doctors and nurses are quarantining newly admitted American patients at international hospitals in Amsterdam, Toronto, and Copenhagen. Why? To assess whether they're infected with methicillin-resistant Staphylococcus aureus (MRSA). The organism is increasingly common in the United States with recent outbreaks hitting not just healthcare facilities, but schools and athletic teams such as the St. Louis Rams, Baltimore Ravens and San Francisco 49ers.
Patients who test positive for MRSA, are greeted by European and Canadian hospital workers donning protective gloves, masks, and gowns. Then, healthcare workers strip off the gear and scrub down vigorously when they leave the room.
MRSA is creating a health hazard in many countries, dwarfing the threat posed by the H5N1 avian flu. As MRSA causes more infections in the general community, concerns abound regarding widespread outbreaks of hard-to-treat microbes.
What Is MRSA?
Staphylococcus aureus, often referred to simply as "staph," is a bacteria commonly found on the skin and nasal mucous membranes of healthy people. It may also be found in chronic sores like those caused by psoriasis or eczema. MRSA is a variant of staph that is resistant to methicillin, the antibiotic most commonly used to treat staph infections.
What Types of Patients Have MRSA?
MRSA has long been a nosocomial infection control nightmare for hospitals. Now, it’s infecting seemingly healthy people in the community, often children, and causing boils, abscesses and cellulitis, which are frequently misdiagnosed as spider bites.
The bacteria already have taken up residence in parts of California, Texas and Georgia. During last year’s influenza season, MRSA emerged as a potential cause of pneumonia, striking young patients with a vengeance: over 90% were admitted to the intensive care unit and about 20% died.
About two million people in the United States, or 0.8% of the population, are estimated to carry MRSA in their nasal passages.
Staphylococcus aureus infects about 300,000 hospital patients a year; the Centers for Disease Control and Prevention found 64% of the Staphylococcus aureus strains in American hospitals were MRSA. The bacteria kills an estimated 13,000 Americans every year making a hospital patient 10 times as likely to die of MRSA as an inmate is to be murdered in prison.
What About Community Associated MRSA?
Staph and MRSA also cause illness in persons outside of hospitals and healthcare facilities. MRSA infections in persons who have not been hospitalized or had a medical procedure (such as dialysis, surgery, or catheters) within the last year are considered community associated MRSA, or CA-MRSA cases. Infections occurring within the community usually manifest as skin infections, such as pimples and boils, and most often occur in otherwise healthy people.
Recent CA-MRSA outbreaks have revealed bacterial strains with
unique microbiologic and genetic properties compared with the
traditional hospital-based MRSA strains. The data suggests
mutations have allowed community strains to spread more easily or
cause more skin disease. Additional studies are underway to
compare the hospital versus community associated MRSA.
At least three different S. aureus strains found in the United States can cause CA-MRSA infections. The CDC works with state and local health departments to gather data from known cases as researchers attempt to determine why certain people get these infections. Pharmaceutical companies are searching for new antibiotics effective against MRSA. Also, longer term solutions are under investigation by these same companies, such as staphylococcal vaccines.
Colonization Versus Infection with MRSA
Colonization refers to presence of microorganisms with growth and multiplication, but without tissue invasion or damage. In the case of MRSA, the body site most commonly colonized is the anterior nares.
Other body sites colonized with MRSA include open wounds, the respiratory tract, perineum, upper extremities, umbilicus (in infants), urinary tract, and axilla. MRSA colonization can serve as a reservoir for the spread of these
microorganisms to others, and can lead to infection in the host. Colonized patients are also known as asymptomatic carriers.
Infection is the entry and multiplication of microorganisms in the tissues of the host leading to local or systemic signs and symptoms of infection.
About the authors:
Dr. Sheila Dunn, president and CEO of Quality America, Inc., holds a doctoral degree in clinical laboratory science. Sarah Alholm, an occupational safety professional, is the OSHA product manager at Quality America.