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Bacterial Infections
The Importance of Controlling Methicillin-resistant Staphylococcus aureus
a report by
Samuel W Jones, MD and Bruce Cairns, MD, FACS
Department of Surgery, University of North Carolina-Chapel Hill
A Normal Part of the Flora It is important for the practitioner to be aware of the high carriage rates of
Methicillin-resistant Staphylococcus aureus (MRSA), first described in the S. aureus and MRSA among both patients and healthcare workers because
1960s,
1
is now endemic in many hospitals, and may account for up to 30% these organisms may be transferred or spread from patient to healthcare
of staphylococcal infections identified in hospital settings.
2
MRSA is an worker, patient to patient, or healthcare worker to patient. The primary route
S. aureus strain that is resistant to all classes of β-lactam antimicrobials, of MRSA transmission within the hospital appears to be from patient to
including penicillins, cephalosporins, and monbactams.
3
S. aureus is a patient, carried on the hands of hospital personnel.
10
MRSA may also exist on
normal part of the flora that colonizes the anterior nares and may spread to objects in the environment and spread from these objects to patients, often via
the skin, but is also an important human pathogen that causes a broad the hands of healthcare workers.
11–13
Environmental or fomite spread may be
spectrum of infections, from the trivial to the life-threatening. substantially underestimated as a route of nosocomial transmission of MRSA.
Staphylococcal organisms are detectable in many parts of the bodies of
both patients and staff. Patients who are either colonized or infected with
The primary route of methicillin-resistant
MRSA probably serve as the major reservoir for MRSA spread within
Staphylococcus aureus transmission
hospitals. Some authors report that about 20% of the population are
always colonized with S. aureus, 60% are intermittent carriers, and 20%
within the hospital appears to be from
never carry the organism.
4,5
Alarmingly, healthcare workers or hospital staff
patient to patient, carried on the hands
are also carriers, with approximately 6% exhibiting nasal carriage of MRSA
in some studies.
6–8 of hospital personnel.
Historically, MRSA has been considered to be a hospital-acquired organism. More Risk in Intensive Care Units
However, colonization and infections associated with community-acquired Infection and colonization with MRSA appears be more frequent in the
strains of MRSA are being reported more frequently. In a recent study of intensive care unit (ICU) than in general hospital wards. The risk of acquiring
pediatric patients in a community outpatient setting, 36% exhibited nasal MRSA in the ICU is increased by the severity of illness,
14
length of stay,
14,15
carriage of S. aureus, including carriage of MRSA in 9% of the patients.
9
intravascular device use,
16
and the intensity of exposure of infected patients
The MRSA carriage rate represented a significant increase compared with to antibiotics.
17
The ICU is important in the wider dissemination of MRSA, as
rates in recent years and has been associated with unique, community- patients in the ICU are discharged to wards throughout the hospital and
based isolates. The molecular and antimicrobial resistance profiles of the often to other hospitals and long-term care facilities.
18,19
Therefore,
community-acquired MRSA strains are distinct from hospital-acquired MRSA infectious control guidelines must be developed to control the spread of
strains; therefore, healthcare providers must be prepared to diagnose, treat, nosocomial transmission of MRSA. Infection control measures include
and help prevent these infections.
3
Conversely, at the time of hospital screening for MRSA on admission, segregation of MRSA-positive patients or
admission, many patients in the US have been identified as nasal carriers of those patients with a history of previous MRSA infection or colonization,
S. aureus, including MRSA, which may fit community- or hospital-acquired attempted eradication of nasal carriage, and good standards of general
resistance patterns. hygiene, especially hand disinfection. Recent studies suggest intranasal
mupirocin treatment may be effective in reducing S. aureus healthcare-
associated infections among patients with S. aureus nasal colonization.
20
Samuel W Jones, MD, is a Surgical Critical Care Fellow in the Department of Surgery at the
University of North Carolina. He has interests in trauma, critical care, and burn injury.
Mathematical models have been used to understand and predict
Bruce Cairns, MD, FACS, is Director of the Burn Intensive Care Unit at the North Carolina Jaycee
nosocomial cross-transmissions and provide a theoretical basis for
Burn Center at the University of North Carolina Hospitals. He has an active laboratory interventions to control infection and resistance.
21
Based on these models,
investigating the immune response to burn injury, and has extensive experience using multiple
effective strategies that would be expected to prevent transmission or
ventilator modes in the management of inhalation injury. Dr Cairns is a Fellow of the American
College of Surgeons (ACS) and is an active member of the American Burn Association (ABA), the
reduce the prevalence of MRSA in hospitals include reducing antibiotic use,
American Association for Respiratory Care (AARC), and the Society of Critical Care Medicine using antibiotics that do not induce resistance, and decreasing length of
(SCCM). He is board-certified in general surgery and surgical critical care.
hospital and ICU stays. Additionally, instituting infection control measures to
disrupt the spread of bacteria, such as restricting the contact between
56 © T OUCH BRIEFINGS 2007
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